RACIAL VARIATION IN SEEDLING
DEVELOPMENT OF DOUGLAS FIR,
PSEUDOTSUGA MENZIESII { MIRB.) FRANCO
by
HERBERT ELMER OWEN, JR.
A THESIS
submitted to
OREGON STATE COLLEGE
in partial fulfillment of
the requirements for the
degree of
DOCTOR OF PHILOSOPHY
June 1951
APPROVED:
Professor of Botany
In Charge of Major
Head
Chairman of
ol Graduate Committee
Dean of Graduate School
ACKNOWLEDGMENTS
Grateful acknowledgment is made for the guidance
and assistance of Dr. William
w.
Chilcote during the
course of this investigation, and for his and Dr.
Frank H. Smith's constructive criticism of this
manuscript.
Acknowledgment is made for the aid which the
Oregon State Board of Forestry and the United states
Forest Service gave by furnishing the seeds which were
used in this study.
The Oregon State College Seed Laboratory is
thanked tor their willingness to let the author use
their facilities.
Special thanks are due Dr. S.M. Dietz and other
members of the faculty of the oregon State College
Department of Botany and Plant Pathology for their
encouragement and aid 1n obtaining facilities with
which to carry out the experiments.
The author desires especially to acknowledge
the infallible support of his wife, without whom he
could never have completed this study.
TABLE OF CONTENTS
Page
INTRODUCTION . • • •
LITERATURE REVIEW
....•
• • • • • • • • •
1
• • • • • • • • • • • • • • •
4
MATERIALS AND METHODS
........ .....
Morphological, Low Temperature and Soil
Drought Resistance Relations • • • • •
Relative Rates of Radicle Elongation and
Temperature Relations • • • • • • • •
Temperature and Germination Relations • •
Comparative Dates of Bud Setting • • • •
PRESENTATION OF DATA • • • • • • • • • •
•
10
•
•
•
19
23
25
26
• •
• •
26
67
75
• •
90
• •
99
• • • • • • • • • • • • • • • • • • • •
111
DISCUSSION
SUll.miA.RY
•
• • •
Variation in Douglas Fir Seedling
Morphology, Resistance to Soil
Drought and Low Temperatures • • • •
Relative Rates 9f Radicle Elongation
and Temperature Relations • • • • •
Temperature and Germination Relations •
General Characteristics of Douglas Fir
Seeds and Seedlings • • • • • • • •
10
.....
• • • • •
.......
BIBLIOGRAPHY • • • • • • • • • • • • •
• •
• • • • •
116
FIGURES
P~e
1.
2.
Map showing approximate locations of the
seed sources • • • • • • • • • • • • • • • •
Method used to determine the relative rates
of radicle elongation • • • • • • • • • • •
14
21
TABLES
Page
1.
2.
List of seed sources used in the morphology,
low temperature, soil drought and radicle
elongation studies • • • • • • • • • • • • •
List of seed sources used in the germination
. . . . . . . . . . . . . . . . . . •
24
statistical analysis of the morphology
exper1men t s • • • • • • • • • • • • • • • •
27
study
4. Results of L.S.D. and Extreme Mean tests
of morphology data • • • • • • • • • • • • •
5. Results of L.S.D. and Extreme Mean tests
31
•••••••••• • •
92
Summary of the characteristics of the seed
sources listed in Table l • • • • • • • • •
9g
of germination data
6.
12
GRAPHS
l.
Average hypocotyl lengths of two weeks
old Douglas fir seedlings grown under
short and long photoperiods • • • • • • • •
2.
Average epicotyl elongation of four and
eight weeks old Douglas fir seedlings
grown under short and long photoperiods
4.
6.
g_
10.
..
Average total shoot height of four and
eight weeks old Douglas fir seedlings
grown under short and long photoperiods • •
Average root lengths of two, four and eight
weeks old Douglas fir seedlings grown under
short and long photoperiods • • • • • • • •
Average root/shoot ratios according to
length of two, four and eight weeks old
Douglas fir seedlings grown under short
and long photoperiods
• • • • • • • • • •
Average root/shoot ratios according to
length of Douglas fir seedlings grown
under short and long photoperiods as
plotted against age • • • • • • • • • • • •
Average root weights of two, four and
eight weeks old Douglas fir seedlings
grown under short and long photoperiods • •
Average shoot weights of two, four and
eight weeks old Douglas fir seedlings
grown under short and long photoperiods • •
Average root/shoot ratios according to
weight of two, four and eight weeks old
Douglas fir seedlings grown under short
and long photoperiods • • • • • • • • • • •
Average cotyledon lengths of Douglas fir
seedlings grown under short and long
photoperiods • • • • • • • • • • • • • • •
4g
50
52
55
61
63
Page
GRAPHS (continued)
11.
12.
13.
14.
Average grams per centimeter of root
length of two, four and eight weeks
old Douglas fir seedlings grown under
short and long photoperiods • • • • •
...
.
Number of two, four and eight weeks old
Douglas fir seedlings killed by the low
temperature treatment • . • • • • • • .
66
..
69
Number of two, four and eight weeks old
Douglas fir seedlings killed by the soil
drought treatment . • • • • • • • • • • • •
71
Dates of bud setting of Douglas fir
seedlings grown under short photoperiod
conditions
• • • • ~ • • • • • • • • •
73
Average radicle length of Douglas fir
seedlings grown at 5°0. at 14, 21, 2g
and 35 days of age • • • • • • • • • • • •
77
16. Average radicle length of Douglas fir
seedlings grown at 10°0. at 14, 21, 2S
and 35 days of age • • • • • • • • • • • •
17.
lS.
19.
20.
21.
22.
79
Average radicle length of Douglas fir
seedlings grown at 15oo. at 7, 14, 21
and 2S days of age. • • • • • • • • • • • •
Aver~e radicle length of Douglas fir
seedlings grown at 2000. at 3, 7, 10
and 14 days of age • • • • • • • • • • • • •
Average radicle length of Douglas fir
seedlings grown at 25°C. at 3, 7, 10
and 14 days of age. • • • • • • • • . • • •
Average radicle length of Douglas fir
seedlings grown at 30°C. at 3, 7, 10
and 14 days of age • • • • • • • • • • • • •
Average radicle length of Douglas fir
seedlings grown at 2000. and 30°0. at 3,
7, 10 and 14 days of age. • • • • • • • • •
S9
Relative rates of germination of Dou51as
fir seeds at 10°0., 15°C., 20°C., 25 C.,
30°0. and alternating temperatures of
2ooc. and 30°C.
94
RACIAL VARIATION IN SEEDLING
DEVELOPMENT OF DOUGLAS FIR,
PSEUDOTSUGA MENZIESII (MIRE) FRANCO
Introduction
Botanists have long recognized sub-units within
a plant species with characteristic morphological.
and physiological attributes.
These sub-units,
commonly called ecotypes, develop from the original
population under the control of environmental
selection.
The number of ecotypes present within a plant
species is strongly influenced by the variability
among the habitats which the species occupies.
Douglas fir (Pseudotsuga Menziesii (Mirb.) Franco)
is a species with a wide geographic distribution.
stands occur from British Columbia to New Mexico,
from the wet coastal ranges to the drier inland
mountains, and from sea level to several thousands
of feet in elevation.
Thus, the presence of many
ecotypes can be reasonably assumed.
In any attempt to delineate eootypes, two distinct possibilities must be recognized: (1) distinct, , very characteristic races may be present;
2
(2) ecotypic distribution may be clinal, that is,
a gradual gradation of characters may occur from one
extreme to the other.
The degree of ecotypic dis-
tinctiveness is controlled by the character of the
environmental gradiants existing within the range
of the species, and the degree of isolation which
has developed.
Delineation of naturally occurring ecotypes
with inherent morphological and physiological characteristics is of great importance in the management
of a tree species.
Particularly is this true of
Douglas fir in the Pacific northwest, where planting
and direct seeding is a common practice.
Intelli-
gent selection of stocking materials requires an
understanding of the genetic variability within and
between races, and the indefinite relation of the
materials to various growing conditions.
One must
not assume that seed bed conditions following clear
cutting are similar to those under which the forest
was naturally established, or that the highest quality
and most productive stock must be of local origin.
Fundamental to the problem of selecting the right
race for the right place, or to a breeding program,
3
is a clearer definition of the kind and degree of
variation between naturally occurring ecotypes.
This research has been directed in such a manner
as to further the recognition of ecotypes of Douglas
fir in the juvenile stage.
The juvenile stage was
selected because the materials can be rapidly obtained,
and inheritance of characters can be observed before
environmental selection and modifications develop •
.Germination and early seedling stages would appear to
be especially correlated with the natural habitat of
the ecotype.
The final goal is to relate these juven-
ile characteristics with the performance of the grown
tree.
This study is of a preliminary nature and much
more investigation is needed to substantiate, verify
and enhance the data obtained.
LITERATT.R E REVIEW
The presence of distinctive variation in a plant
species has long been recognized by botanists.
Kerner
(27) in 1895 describes what are probably the first
attempts to isolate ecotypes experimentally.
Kerner also
recognized the importance of heredity and relative fixation of certain plant characteristics as opposed to environmentaLly imposed modifications.
Bonnier (8), in
a series of experiments extending over a period of thirty
years, described ecotypic variation, but failed to differentiate between hereditary and environmental variation.
The eootype concept, as known today, probably stems
the European botanist Turesson's investigations
<46, 47,
48, 49). Turesson originally defined the term ecotype
as "the product arising as a result of the genotypical
response of an ecospecies or species to a typical
habitat~"
<46). MacDougall (29) and Clements (14) were early pioneers in the extensive study of ecotypes in America.
Clausen, Keck and Hiesey (12, 13) have probably contributed
the most extensive store of knowledge concerning the
ecotype concept in America.
The presence of two types of ecotypic variation in
plant populations is now well accepted:
(1) very dif-
ferent and easily recognized ecotypes, and (2) continuous
5
or clinal variation in which a given species of plant exhibits intermediate gradients of morphological and physiological characteristics between two or more extreme
populations
<45).
As early as 1913, Engler (19) de-
scribed a clinal ecotype development in Pinus sylvestris
L.
Other investigators have found similar
tributions in other species (7, 19, 22,
35,
eco~tpe
4>•
dis-
Clinal
development appears to occur most abundantly in widely
and continuously distributed plant species
ligate cross pollination (48).
<45),
with ob-
When distinctly different
ecotypes are present within a plant species, the species
distribution is usually a discontinuous one, or the ecotypes represent the extremes of a continuous species population
C45).
Although many scattered references indicate the
presence of ecojiyp.e s in Douglas fir, a clear definition
of their characteristics and habitats has not been developed.
As early as 1909, Frothingham (20) published
material citing the presence of three varieties of Douglas
fir:
(l) P. taxifolia var. viridis; (2) P. taxifolia
var. caesia; and, (3) P. taxifolia var. glauca.
The
viridis, or green, variety occurs in the northwest; the
caesia, or gray, variety comes from the intermountain
6
region; and, the glauca, or blue, variety occurs in the
Rocky Mountain region.
Richens (41), Busgen and Munch
(11) and Boyce (9) have reported varying insect and pathogen resistance between these three for.ms of Douglas fir.
Munger (33), Isaac
(~)
and Kanzow (26} have reported
racial variation to certain diseases within both the Rocky
Mountain form and the northwest form of Douglas fir.
Jackson (17) lists twelve varieties of Douglas fir based
on foliage variation.
Pearson (39) has shown the presence of Douglas fir
ecotypes in the southwest.
Isaac
(~)
has reported alti-
tudinal variation in Douglas fir with regards to frost
resistance in trees twenty to twenty-three years old.
Kummel, et al (28) and Paul (37) reported variation in
growth characteristics of older trees with regards to
altitude of seed source.
The most comprehensive data concerning Douglas fir
racial variation is found in the reports of Munger and
Morris (32, 33).
The above workers collected seed from
thirteen widely separated localities in western Oregon
and
Washington in 1911 and established plantations vary-
ing in elevation from 1000 feet to 4600 feet above sea
level.
Each plantation contained trees from each of the
1
thirteen seed sources.
Growth and survival data were
collected at five year intervals.
iations have been observed.
Apparent ecotypic var-
As a result of these inves-
tigations, nine major provenances have been outlined and
published by Kummel, et al (28) for Douglas fir in the
Pacific northwest.
Day length treatments have been used by a number of
researchers to demonstrate ecotypic differences w.ithin
species of wide geographic distribution.
Olmsted (35),
in a very comprehensive investigation of the grass species
Bouteloua curtipendula (Michx.) Torr., has shown distinct
differences between geographic races in their response to
photoperiod variation.
Pauley and Perry (38) have reported
varied day length responses between certain geographical
races of the genus Populus.
Vaartaja (50) has demonstrated
the presence of morphologically different ecotypes in
Pinus sylvestris and Alnus incana (L.) Moench, When the
seedlings are grown under varying photoperiods.
He round
that northern seedlings exhibited a more pronounced
photoperiodic response than did aouthern seedlings. Jester
and Kramer's (25) experiments substantiate the latter
observation.
Irgens-Moller (23) has separated various
ecotypes of Quercus borealis
~.
on the basis of photo-
periodic response, and noted differences in growth and
8
frost resistance.
Wareing (52, 53) has shown that the
advent of dormancy in the fall and the breaking of dormancy in the spring in Pinus sylvestris is controlled by
photoperiod.
No literature could be found concerning the
photoperiodic response of Douglas fir.
Many instances of ecotypic variation in seedling
drought and frost resistance have been recorded.
Pinus
(54), Pinus ponderosa Laws. C41, 42), Pinus
resinosa Ait. (5, 1), Pinus taeda L. (56) and Fraxinus
sylvestris
Pennsylvanica Marsh. {2, 30, 31) are but a few of the tree
species in which ecotypes have been shown to exhibit varying resistances to drought and frost.
The only report
directly concerning Douglas fir is Lawrence's report (24)
concerning relative drought resistances exhibited by two
races of Douglas fir seedlings.
Rudolf (43) and Baldwin
(3) have published lists of tree species which have been
observed to have ecotypes with variable frost and drought
resistances.
Burton {10) has shown racial variation in the germinative capacity of seeds from different seed sources in
Robinia pseudoacacia L., as has Bates {6) in Pinus resinoaa
and Pearson (40) in P. ponderosa.
~
Seeds of Prunus Ameri-
Marsh of northern and southern origin have been shown
9
to exhibit distinct differences in their temperature
requirements for germination (21).
Little is known of
the variation in germination requirements for Douglas
fir seeds from various localities within the range of
the species.
Little work has been conducted to distinguish
variations in the juvenile stages of apparent ecotypes
within a tree species.
Investigators have concentrated
on growth at the end of the first year and in subsequent annual increments.
Cummings and Blow (16),
Cummings (15), and Spurr (44) have noted differences
between geographic races in pine seedlings.
Recently
in the southern pine region of the United States, experiments have been designed and are now in progress, to
study variation in the juvenile stages of the native
pines (18).
10
Materials and Methods
The seeds used in this study were obtained rrom
the Oregon State Board
States Forest Service.
the
or
Forestry and the United
All seeds were harvested during
1952 season.
Table one lists the various seed sources by state,
county and elevation.
Speciric details
or
the site,
seed trees and harvesting conditions could not be obtained.
All seed lots exhibited cutting tests of
ninety-five per cent or better.
The general localities from which the collections
were made appear in the accompanying map (Figure 1).
Numbers outside the parenthesis refer to the areas
where seeds were collected for morphology, low temperature, soil drought and radicle elongation studies.
Numbers with the sub-letter A and within parenthesis
refer to the localities where the seed used in the
germination experiment were collected.
Morphological, Low Temperature and Soil
Drought Resistance Relations
Morphological and physiological characters of the
11
seedlings from the various seed sources listed in
Table one were studied under controlled greenhouse
conditions.
Seedlings from the nine seed sources were
grown under nine and sixteen hour daylengths.
Low
temperature, soil drought resistance and morphological
studies were conducted with seedlings of two, four
and eight weeks of age.
Since photoperiod could be
easily controlled and since an ecotypic response to
long and short photoperiods has been observed in other
tree species (38, 50, 23), long and short photoperiods
of sixteen and nine hours respectively were selected
as master treatments in this preliminary investigation
of Douglas fir ecotypes.
Seedlings used in these studies were grown in an
Oregon State College greenhouse during the summer and
spring of
1954.
The four and eight-weeks old seedlings
used in the morphological studies were grown in boxes
thirty inches deep and thirty inches square.
These
boxes were constructed of one by six tongue and groove
boards and placed on four by four stringers on the
greenhouse floor.
Aiken silty-clay loam soil was
placed in the boxes on top of a three inch layer of
gravel.
The gravel was used to facilitate drainage.
The two weeks old seedlings used in the morphological
12
Table 1
List of seed sources used in the morphology, low
temperature, soil drought resistance, and radicle
elongation studies.
Code Nmnber
countz
State
Elevation
1
Jackson
Oregon
4ooo-45oo feet
2
Pierce
Washington 1500 feet
3
Douglas
Oregon
1200 feet
4
Douglas
Oregon
3500-4000 feet
5
Jefferson Washington 500-1000 feet
6
Well
Montana
6000 feet
7
Park
Colorado
7500 feet
8
Polk
Oregon
0-500 feet
9
Linn
Oregon
500 feet
North Slope
13
Figure 1.
Map showing approximate location of seed sources
used in this study.
Numbers out of parenthesis refer
to seed sources listed in Table one.
Numbers in
parenthesis with the letter A addended represent the
seed sources listed in Table 2.
Figure 1.
1.5
studies and the four and eight weeks old seedlings
used in the physiological experiments were grown in
large greenhouse flats ten inches in depth.
One complete set of seedlings was grown under short
(nine hours of daylight) photoperiodic conditions.
These seedlings were covered for fifteen hours of the
day by three thicknesses of black percale cloth suspended from a frame located two feet above the top of
the boxes.
This cloth was weighted with lath strips
about the base.
The lath were held against the sides
of the boxes by nail pivoted boards.
The seedlings
were in complete darkness when this cloth was placed
above them.
Another seedling set was maintained at a sixteen
hour day by means of two banks of four-tube fluourescent lamps and tbree three hundred watt incandescent
lamps connected to an automatic time switch.
These
lamps were suspended approximately four feet above the
box tops.
Extension bulb thermographs showed that the effect
of supplemental light in the extended dawlength treatment and the cloth covering under the short daw treatment did not create significantly different temperature
i6
conditions.
This was probably due to good ventilation
and the position of the greenhouse used.
This green-
house was shaded on both the east and west sides from
the morning and late afternoon sun, and since the
black cloth was removed during the period of direct
sunlight, the high temperatures which might have been
expected under the black cloth did not develop.
The seedlings used in the morphological experiment
were removed from the boxes for measurement by removing the sides of the boxes and gently ·w ashing the soil
from the roots.
The seedlings were then placed in
gallon cans of water and measurements taken within a
twenty-four hour period following removal from the soil.
Morphological characters measured included:
(1)
length of the hypocotyl; (2) root length; (3) epicotyl
elongation; (4) total shoot length; (5) oven-dry root
weight; (6) oven-dry shoot weight; and (7) cotyledon
length.
Root/shoot ratios were calculated from the
root and shoot length and weight data obtained.
Measurements of the roots and shoots of the seedlings were made with the definite constriction occurring
at the base of the hypocotyl serving as a reference
point for the base of the shoot and top of the root.
17
The base of the cotyledons was used to mark the top
of the hypocotyl and tip of the epicotyl was used as
an end point for both epicotyl elongation and total
shoot length measurements.
Root lengths were measur-
ed from the constricted area to the root tip which
was checked for breakage with a hand lens.
Oven-dry
weights of the roots and shoots were obtained from
the same seedlings from which the length measurements
were taken.
An oven at 100° F. was used to dry the
seedling parts.
Root/shoot ratios were calculated from
the above figures.
Average cotyledon lengths were de-
termined by averaging the lengths of five cotyledons
on each seedling.
The oven-dry weight per centimeter
of root length was calculated from the root lengths
and weights determined by the above measurements.
All statistics obtained from these data were incqrporated into a randomized block factorial design
for statistical analysis.
This design included the
two photoperiods, nine seed sources and three age
groups mentioned previously.
Three groups of five
seedlings each served as three replicates.
To determine comparative low temperature resistances, boxes of seedlings each containing three groups
18
of ten even-aged seedlings from each seed source and
photoperiod were placed in a cold room at 0° F. for
forty minutes.
This time and temperature treatment
was derived from experience with preliminary experiments as the best for all ages.
A more moderate treat-
ment would have obtained better ecotypic separation in
the two weeks old seedlings.
In the soil drought experiment, boxes containing
three groups of ten even-aged seedlings from each seed
source were sown with barley seven to ten days prior
to treatment.
The barley served to remove the soil
moisture rapidly and to provide a uniform wilting point.
The treatment used was derived from preliminary experiments.
A more moderate treatment would have affected
better ecotypic separation in the two weeks old seedlings.
The treatment consisted of allowing the seed-
lings to remain under soil moisture conditions below
the permanent wilting point of the barley for ten days.
The data from both the low temperature and soil
drought resistance studies were analysed statistically
in a factorial design.
The number of seedlings killed
in each group of ten even-aged seedlings was used as
the statistic, with the three groups serving as repli-
19
cates within a seed source.
Relative Rates
~
£! Radicle Elongation
Temperature Relations
The ability of a seedling's radicle to penetrate
the soil rapidly as optimum soil moisture conditions
recede during the early part of the growing season rates
high on the list of desirable survival characteristics.
Therefore, if differential rates of radicle elongation
exist between ecotypes, a knowledge of the various
rates would be advantageous.
In a preliminary inves-
tigation, such variation was observed; also, differences in the rates of radicle elongation of seedlings
from early and late germinating seeds were noted.
The
following procedure was devised from the preliminary
trials.
The seeds were germinated at
250 c.
A seed was
considered to be germinated when the radicle protruded
two to three millimeters.
Three groups of five germin-
ated seeds each, from a single seed source, were placed
radicle do\vn three inches from the top of two moistened
sheets of germination paper which were twelve inches
high and sixteen inches
~ong.
Two more sheets of
20
moistened germination paper were then placed over the
three groups of seeds.
These four sheets were then
rolled into a cylinder and placed in a battery jar containing approximately one inch of tap water.
The tap
water served to keep the germination paper moist throughout the experiment.
Each battery jar eventually con-
tained a roll of germinated seeds from each seed source.
The battery jar was then placed in one of the various
temperature chambers used.
The first twenty-five per
cent of the seeds to germinate were compared with the
last twenty-five per cent to germinate.
(Figure 2).
At intervals, the rolls were removed, unrolled and the
radicle length measured.
After measurement of the rad-
icles, the seedlings were rerolled and returned to the
temperature chambers until the next interval.
This experiment included six ages:
three, seven,
ten, fourteen, twenty-one and thirty-five days; seven
temperature treatments:
/~0
c.,
10 0
c.,
1/~0
c.,
20 0
c.,
25° c., 30° c. and alternating 20°-30° c.; the nine
seed sources listed in table one; and the two germination groups.
In the lower temperature treatments,
radicle elongation was too slow to measure at the early
ages, and at the higher temperatures, maximum radicle
21
Figure 2.
The experimental method used to determine relative rates of radicle elongation of seedlings from
various seed sources.
22
Figure 2.
elongation was attained before the later ages were
reached.
Temperature and Germination Relations
Relative germination rates of the seeds from the
sources listed in Table 2 were determined by use of
the facilities of the Oregon State College Seed Laboratory.
Before treatment, all seeds were soaked for
twenty-four hours at 25°c., drained and stored at 2°c.
for one week.
This procedure is the type of stratifi-
.cation used by the
Orego~
State College Seed Laboratory
in their germination tests of Douglas fir seeds.
Each seed source was represented in each treatment
by three petrie plates containing fifty seeds each.
The following temperature treatments were used:
10°C.,
150 c., 20 0 c., 25 0 c., and 300 c. and an alternating temperature chamber set at 20°C. and 30°C.
At three, five,
seven, ten, fourteen, twenty-one and twenty-eight day
intervals the petrie plates were removed from the
chambers and counts of the germinated seeds were made.
The germinated seeds were removed at each count and
the petrie plates returned to the chamber until the
next count.
At the end
of~wenty-eight
days, any seeds
Table 2
Seed sources of seeds used in germination study.
The approximate location of these sources are shown
on Figure 1.
Code Number
Countz
State
Elevation
lA
Park
Colorado
7500 feet
2A
Well
Montana
6ooo feet No. Slope
~
3A
Well
Montana
6ooo feet So. Slope
4A
Jackson
Oregon
4500 feet
5A
Douglas
Oregon
3500 feet
6A
Linn
Oregon
500 feet
7A
Columbia
Oregon
200 feet
8A
Lane
Oregon
500 feet
9A
Marion
Oregon
506 feet
lert ungerminated were considered to be incapable of
germination under the conditions of the experiment.
The Least Signiricant Difrerences between the
number of seeds germinated from each seed source at
each temperature were used to statistically analyse
the data.
Comparison of Dates of Bud Setting
In other tree species (23, 38, 52, 53), the date
of bud setting has been shown to constitute an ecotypic reaction.
Also earliness or bud setting, frost
and drought hardiness have been directly correlated in
other tree species (38, 52, 53).
To see ir such a
correlation existed in Douglas fir, the following experiment was designed.
Seedlings used in the morphology experiments grown
under short photoperiods were observed daily ror setting
of the terminal buds.
When one-halr or more of the
seedlings exhibited bud scales on the terminal buds,
the buds were considered to be "set" or in a state or
dormancy, and the date was recorded.
26
PRESENTATION OF DATA
Variation in Douglas Fir Seedling
Morphology, Resistance to Soil
Drought and Low Temperatures
In a three-way factorial experiment involving
different seed sources, long and short photoperiodic
treatments, and three age groups, the data showed
significance according to Table 3.
analysis, L.
s.
Further statistical
D. and Extreme Means tests, determined
the exact points of interaction and single factor
affectiveness.
(See Table
4).
In all instances, un-
less otherwise stated, an increase in age and the long
photoperiod treatment resulted in an increase in the
magnitude of the morphological characters.
Photoperiod apparently had no effect on the
of the hypocotyl in most seedlings.
gro\~h
However, seedlings
from Colorado and Montana had much shorter hypocotyls
when grown under short photoperiods, and seedlings from
No. 1 had much longer hypocotyls when grown under short
photoperiodic conditions.
Number 1 seedlings had the longest hypocotyls,
while seedlings from Nos. 6 and 7 had the shortest hypocotyls.
Numbers 2, 3,
4, 5
and 9 seedlings had
Table 3
Statistical Analysis
Morphology Experiments
Seedling
Characteristic
Source of
Variation
Hypocotyl
Length
Photoperiods
Sources
Sources x Photoperiods
Epicotyl
Elongation
Total Shoot
Length
Root
Length
Photoperiods
Ages
Sources
Photoperiods X Ages
Photoperiods X Sources
Sources x Ages
Photoperiods x Ages x Sources
Photoperiods
Ages
Sources
Photoperiods X Ages
Photoperiods X Sources
Sources x Ages
Photoperiods X Ages x Sources
Photoperiods
Ages
Sources
Photoperiods
Photoperiods
Significant
Not
Significant
·;}
*
{~
-~
·'"'
#\
{~
*
-::·
·:'"
{~
-~~
~~
·!:·
-~
~~
-~
{~
..:~
X
X
Ages
Sources
*
*
..
·~~
N
-..:J
Seedling
Characteristic
Source o:f
Variation
Root
Length
Sources x Ages
Photoperiods x Ages x Sources
-:~
Root/Shoot
Ratio by
Lengths
Photoperiods
Ages
Sources
Photoperiods X Ages
Photoperiods X Sources
Sources x Ages
Photoperiods X Ages x Sources
-~
Shoot
Weight
Root Weight
Photoperiods
Ages
Sources
Photoperiods X Ages
Photoperiods X Sources
Sources x Ages
Photoperiods X Ages x Sources
Photoperiods
Ages
Sources
Photoperiods X Ages
Photoperiods x Sources
Sources x Ages
Photoperiods x Ages x Sources
Signi:ficant
Not
Significant
-~
*
**
i~
-~
-:~
*
{~
.:}
-~
"
··~
-~
*
-~
{}
-:~
·:~
·:}
~-
N
(X)
Seedling
Characteristic
Source o:r
Variation
Root/Shoot
Ratio by
Weight
Photoperiods
Ages
Sources
Photoperiods X Ages
Photoperiods x Sources
Sources x Ages
Photoperiods x Ages x Sources
Cotyledon
Length
Root Weight
Per Root
Length
Frost
Resistance
Photoperiods
Sources
Photoperiod x Sources
Photoperiods
Ages
Sources
Photoperiods X Ages
Photoperiods x Sources
Sources x Ages
Photoperiods x Ages x Sources
Photoperiods
Ages
Sources
Photoperiods X Ages
Photoperiods x Sources
Sources x Ages
Photoperiods x Ages x Sources
Signi:Cic ant
Not
Signi:Cicant
{-ti~
-'~
"
~~
-:}
~~
*
·U
-:~
i~
·:to
*
*·:to
-:~
-~
*
~~
*
i~
.
~
{~
~t-
*
N
""
Seedling
Characteristic
Source of
Variation
Soil Drought
Resistance
Photoperiods
Ages
Sources
Photoperiods x Ages
Photoperiods x Sources
Sources x Ages
Photoperiods x Ages x Sources
Significant
*
*
*
*
~~
Not
Significant
Table
Results
istics
o~
o~
4
L.S.D. and Extreme Mean tests according to the character-
the seedlings and sources
o~
variation.
Numbers correspond to
the numbers of the seed sources listed in Table one.
Seedling
Characteristic
Source of
Variation
Results o~ L.S.D. and
Extreme Means Tests
Hypocotyl
Length
Sources - Short Photoperiod
Sources - Long Photoperiod
Photoperiod x Sources
1 2,4,9,3,5 8 6,7
1,4,2 3,5,8,9 6,7
Epicotyl
Elongation
Sources
At 4
Sources
At 8
Sources
At 4
Sources
At 8
Total Shoot
.· Length
Sources - Short Photoperiod
At 4 Weeks
- Short Photoperiod
Weeks
- Short Photoperiod
Weeks
- Long Photoperiod
Weeks
- Long Photoperiod
Weeks
1 short
6 short
7 short
1 long
6 long
7 long
1,3,4,5,8,9 2,7 6
5 2,3,4,8 1 9 7 6
1,2,3,4,5,8 9 6 7
2~3,4 1,8 5 9 7 6
1 2,3,4,5,8,9 6,7
Table
4
Seedling
Characteristic
Source of
Variation
Results of L.s.D. and
Extreme Means Tests
Total Shoot
. Length
Sources - Short Photoperiod
At 8 Weeks
Sources - Long Photoperiod
At 4 Weeks
Sources - Long Photoperiod
At 8 Weeks
Age - Short Photoperiod
2,4,5,8 1,3,9 6,7
Root
Length
Sources - Short Photoperiod
At 2 weeks
Sources - Short Photoperiod
At 4 Weeks
Sources - Short Photoperiod
At 8 Weeks
Sources - Long Photoperiod
At 2 Weeks
Sources - Long Photoperiod
At 4 Weeks
Sources - Long Photoperiod
At 8 Weeks
Sources
Photoperiod
1,4,5,8,9 2,3 6,7
5 1,2,3 4,8 9 6,7
6,7 Exhibited No Growth
1,6,7 2,3,4,8,9 5
1,2,6,7,8,9 3,4,5
6,7 1,4 9,2 3,8 5
1,6,7,9 2,3;4,8 5
1 4,6,7,9 2,3,5 8
1,6,7,9 3,4 2,8 5
1,6,7 2,3,4,9 8 5
Long Short
Table 4
Seedling
Characteristic
Source of
Variation
Results of L.S.D. and
Extreme Means Tests
Root/Shoot
Ratio by
Length
Sources - Short Photoperiod
At 2 Weeks
Sources - Short Photoperiod
At
Weeks
Sources - Short Photoperiod
At 8 Weeks
Sources - Long Photoperiod
At 2 Weeks
Sources - Long Photoperiod
At 4 Weeks
Sources - Long Photoperiod
At 8 Weeks
Sources
Photoperiods
Ages
6 7 1,2,3,4,5,8,9
Shoot Weight
4
Sources
At 2
Sources
At 4
Sources
At 8
- Short Photoperiod
Weeks
- Short Photoperiod
Weeks
- Short Photoperiod
Weeks
6 2,7,8,9 1,3,4,5
6,7 1,9 2,3,4, 5,8
6,7 1,9 2,3,4,8 5
6,7 1,2,3,4,9 5,8
6,7 9 1,8 2,3,4, 5
6,7 1,9 2,3,4,8 5
Long Short
2 Weeks 4 Weeks 8 Weeks
1,2,3,4,5,8,9 6,7
li2,8,9 3,4,5 6,7
8 2 3,4,5 9,1 6,7
\,..)
\,..)
Table
4
Seedling
Characteristic
Source or
Variation
Results or L.S.D. and
Extreme Means Tests
Shoot Weight
Sources - Long Photoperiod
At 2 Weeks
Sources - Long Photoperiod
At 4 Weeks
Sources - Long Photoperiod
At 8 Weeks
Sources
Photoperiods
1,9 2,3 4,5,8 6,7
1,4,9 2,3,5,8 6,7
8 1,5 2,3,4,9 6,7
Sources - Short Photoperiod
At 2 Weeks
Sources - Short Photoperiod
At 4 Weeks
Sources - Short Photoperiod
At 8 Weeks
Sources - Long Photoperiod
At 2 Weeks
Sources - Long Photoperiod
At 4 Weeks
Sources - Long Photoperiod
At 8 Weeks
Sources
Photoperiods
8 1,2,3,5,9 4 6,7
8 3 1,2,4,9 5 6,7
2,8 1,3,4,9 5,6,7
5,8 2,3,4,9 1,4 6,7
Root Weight
1,8 2,3,4,5,9 6,7
Long Short
8 5 1,2,3,4,9 6,7
58 9 2,3 1,4 6,7
5,8 2,3,9 1,4 6,7
Long Short
\.1.)
-f="*
Table
4
Seedling
Characteristic
Source of
Variation
Results of L.S.D. and
Extreme Means Tests
Root/Shoot
Ratio by
Weight
Sources - Short Photoperiod
At 2 weeks
Sources - Short Photoperiod
At 4 Weeks
Sources - Short Photoperiod
At 8 Weeks
Sources - Long Photoperiod
At 2 Weeks
Sources - Long Photoperiod
At 4 Weeks
Sources - Long Photoperiod
At 8 Weeks
Sources
Photoperiods
2' 3' 5' 8 1' 4·, 6' 7' 9
Cotyledon
Length
Sources
Root Weight
Per Length
Sources
At 2
Sources
At 4
8 3,4 2,6,9 7 1
6 1,2,3,4,7,9 8 5
4,8 2,3,5 1,6,7,9
8 5 2,3,4 1,9 6,7
4,5,8,9 2 3 1,6,7
8 2,3,4,5 9 1,6,7
Long Short
i 2,3,4,8,9 5 6,7
- Short Photoperiod
Weeks
- Short Photoperiod
Weeks
5,8 2,3,9 1,4 6,7
8 3 1,2,4,5,9 6,7
Table
4
Seedling
Characteristic
Source of'
Variation
Results of' L.s.D. and
Extreme Means Tests
Root Weight
Per Length
Sources - Short Photoperiod
At 8 Weeks
Sources-Long Photoperiod
At 2 Weeks
Sources - Long Photoperiod
At 4 Weeks
Sources - Long Photoperiod
At 8 Weeks
Sources
Photoperiods
8 2 3,4 1,5,9 6,7
Resistance to
Low Temperatures
Frost
Resistance
5 8,4 2,3,9
1
2,4,5 3,9
1
8
6,7
6,7
5,8 4,9 3 1,2 6,7
8
5 2,3,9 1,4 6,7
Long Short
Sources
At 2
Sources
At 4
- Short Photoperiod
Weeks
- Short Photoperiod
Weeks
6 7
1
9 2,3,4,5,8
6,7
1
9 2,3,4 5,8
Sources
At 8
Sources
At 2
Sources
At 4
Sources
At 8
Sources
- Short Photoperiod
Weeks
- Long Photoperiod
Weeks
- Long Photoperiod
Weeks
- Long Photoperiod
Weeks
1,6,7 4,9, 2,3 5,8
6,7
1
9 2,3,4,5,8
6,7
1
9
4 2,3 5,8
1,6,7 4,9 2,3 5,8
6,7
1
9 2,4 3 5,8
Table
4
Seedling
Characteristic
Source of
Variation
Results of L.S .D. and
Extreme Means Tests
Soil Drought
Resistance
Sources
At 2
Sources
At 4
Sources
At 8
Sources
At 2
Sources
At
Sources
At 8
Sources
6,7 1,9 2,3,1+,5,8
6,7 1,9 4 2,3,5,8
1,6,7 9 4 2,3 5,8
6,7 1,9 2,4 3,5,8
4
- Short Photoperiod
Weeks
- Short Photoperiod
weeks
- Short Photoperiod
Weeks
- Long Photoperiod
Weeks
- Long Photoperiod
Weeks
- Long Photoperiod
Weeks
6,7 1,9 2,3 4 5,8
6,7 1 9 2,3,4 5,8
6,7 1 9 2, 3,lf. 5' 8
hypocotyls of approximately equal lengths.
(See
Graph 1).
The epicotyl elongation of all seedlings was
greatly reduced by the short photoperiod treatment,
but in some cases more so than in others.
growth of seedlings from Nos.
Epicotyl
1,6 and 7 was reduced
the most by the short photoperiodic treatment, while
the epicotyl growth of seedlings from No. 5 was the
least reduced.
Numbers 2, 3,
4 and
8 are similar
in their epicotyl growth response under the short
photoperiodic treatment.
Under long photoperiodic treatment, seedlings
from Nos. 1, 2, 3,
4,
5 and 8 had the greatest
epicotyl growth at four weeks of age; Nos.
9 exhibited the least amount of growth.
6, 7 and
At eight
weeks of age, seedlings from Nos. 2, 3, and
4 had
the
greatest amount of epicotyl growth, followed by seedlings from Nos. 1 and 8,
5, 9,
7 and 6 in that order.
(See Graph two).
At four weeks of age, the total shoot growth
was not affected by photoperiodic variation, but
at eight weeks of age, a marked shoot shortening
39
Graph 1
Average hypocotyl lengths in centimeters of
two weeks old Douglas fir seedlings from nine seed
sources, grown under long and short photoperiods.
Solid bars represent short photoperiodic conditions,
while dotted bars represent seedlings grown under
long photoperiods.
4.5
0
...:::r
4.0
3.5
~
~ 3.0
~~
~~ 2.5
~~
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,.q
~
H
C1
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~ 1.5
~
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1.0
0.5
QO
4
5
SOURC£5
6
7
9
Graph 2
Average epicotyl elongation in centimeters
of four and eight weeks old seedlings of Douglas
fir, from nine seed sources grown under short
(solid bars) and long (dotted bars) photoperiods.
"'~
5
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Graph 2
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occurred under the short daylength conditions.
Seed
source one seedlings had the longest total shoot
length at the four weeks age interval, closely followed by seedlings from Nos. 2,3,4,5,8 and 9·
Seedlings from Nos. 6 and 7 had the smallest shoot
lengths.
At eight weeks of age, under long photo-
periods, seedlings from No.
5
had the longest shoot
lengths, closely followed by seedlings from Nos. 1,
2 and 3.
Numbers
4 and
8 seedlings were in the
next smallest group, followed by seedlings from No.
9.
Seedlings from Nos.
6 and 7 had the shortest
shoot lengths.
Under short photoperiodic treatment, at eight
weeks of age, seedlings from Nos. 2,
4, 5,
and 8 had
the longest shoot lengths, closely followed by seedlings from Nos. 1,
3 and 9.
Seedlings from Nos.
6
and 7 exhibited little shoot growth between four and
eight weeks of age.
(See Graph 3).
Under long photoperiods seedlings from Nos. 6
and 7 had the longest roots, closely followed by
seedlings from Nos.
4 and
9.
Seedlings from Nos. 2
and 3 were intermediary with regards to root lengths,
and seedlings from Nos.
5
and 8 had the shortest roots.
Short photoperiodic treatment shortened all root
Graph 3
Average total shoot height in centimeters of
four and eight weeks old Douglas fir seedlings
for long and short photoperiods from nine seed
sources.
Solid bars represent seedlings grown
under long photoperiods, while dotted bars reppresent seedlings grown under short photoperiods.
\!\
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46
lengths, but the rankings remained the same.
Graph
(See
4>.
One of the more revealing morphological
characters of the seedlings may be found in the
root/shoot ratios according to length.
Under both
long and short photoperiodic treatments, the rankings remain
~proximately
the same, but the short
photoperiodic treatment accentuated the differences
between the seedlings from the
vario~s
seed sources.
Seedlings from Nos. 6 and 7 had by far the
largest root/shoot ratios, with seedlings from Nos.
1,
4 and
9 having the next largest root/shoot ratios.
Seedlings from Nos. 2 and 3 were next in line, with
Nos. 5 and 8 having the smallest ratios.
(See Graph
5).
Under long photoperiods, the root/shoot ratios
according to length followed a rising-falling type
of curve with the maximum root/shoot ratios reached
at four weeks of age.
However, under short photo-
periodic conditions, most of the seedlings exhibited
a falling-rising type of curve with the minimum
ratios occurring at four weeks of age.
6).
(See Graph
47
Average root lengths in centimeters of
Douglas fir seedlings from nine seed sources at
two, four and eight weeks of age under long
(dotted bars) .a nd short (solid bars) photoperiods.
48
25
20
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Graph
4
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7
8
9
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:·..
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'---
49
Graph 5
Average root/shoot ratios according to length
or two, four and eight weeks old seedlings or
Douglas fir, from nine seed sources, grown under
long (dotted bars) and short photoperiods (solid
bars).
50
6
Q
::
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;.
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~~ 2
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:
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6
<5~
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::i~ 2
(\1
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3
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4
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6
50l1RCE5
Graph
5
'•
::
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....
....
..
....
7
B
....
....
:
..
.•
..
:
....
.•
..
9
51
Graph 6
Root/shoot ratios according to length of Douglas
fir seedlings from nine seed sources at two, four
and eight weeks of age.
Numbers of points corres-
pond to seed source numbers listed in Table one.
(\J
\t\
7
6
6
0
~
7
1
5
q
tl:
~
"'..c:
4
p.
.e
C)
C)
~
3
8
1::0
!S
~
(:':)
ct
'
2
2
I
0~--~--------~--------~~------~~~~--------~--------~--------~~
2
4
6
LONG PJIOTOPE'RIOD
'WEEKJ
6
2
4-
6
SHORT PHOTOPERIOD
'WeEKS
8
CIS
H
0
53
The oven-dry weights of the seedlings' roots
follow the same seed source ranking pattern under
both photoperiods; Nos.
5 and 8 were the heaviest,
followed by seedlings from No.
9; seedlings from
Nos. 2 and 3 came next in line, followed by seedlings from Nos. 1 and
4.
Seedlings from Colorado
and Montana had the lowest root weights.
Roots
grown under the short photoperiod were always lighter than roots grown under long photoperiodic con(See Graph 7).
ditions.
The oven-dry weights of the shoots were distinctly affected by varying photoperiodic conditions.
Long photoperiods always increased the oven-
dry weight of the shoot.
Under the long photoperiod,
at all ages, except at eight weeks of age where
they had second ranking, seedlings from Nos. 1 and
9 had the heaviest shoots.
3,
4 and
Seedlings from Nos. 2,
5 were usually of an intermediary nature
with regards to their shoot weight, with seedlings
from Nos,
4
and
5
nearly always slightly heavier
than seedlings from Nos. 2 and 3.
Numbers 6 and 7
seedlings always had the lightest oven-dry shoots.
54
Graph 7
Average root weights of Douglas fir seedlings
from nine seed sources at two, four and eight weeks
of age grown under long (dotted bars) and short
(solid bars) photoperiods.
55
80
·:
::
70
....
"'
60
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50
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30
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30
i::j
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~VI 20
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...·
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.
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4
5
6
SOURCES
Graph 7
7
B
·:
..·:
..
..
9
56
Under short photoperiodic conditions at two
and four weeks of age, the ranking of the seed
sources with regards to oven-dry weights of the
shoots was the same as noted for long photoperiods.
When the short photoperiod seedlings were eight weeks
old, the rankings in order of diminishing weights
were:
2 and 8; 3,
4
and 5; 1 and
9; 6 and 7.
(See Graph 8).
The root shoot ratios according to weight
were also reduced in the seedlings grown under
short photoperiodic conditions except when the seedlings came from Nos. 1,
6 or 7.
Seedlings from Nos.
l, 6 and 7 had greater root/shoot ratios according
to weight when grown under short photoperiodic conditions than when grown under long photoperiods at
eight weeks of age, and short photoperiod seedlings
from No. 6 also had larger ratios than long photoperiod seedlings at four weeks of age.
Under long photoperiodic conditions, the general
ranking of the seed sources was the same at all ages
with regards to root/shoot ratios according to weight.
Under short photoperiodic conditions, the rankings
57
Graph 8
Average shoot weights of Douglas fir seedlings
from nine seed sources at two, four and eight weeks
of age under long (dotted bars) and short (solid
bars) photoperiods.
58
70
........
..
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60
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50
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20
::
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•,
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6
50tJ.RCE5
Graph 8
......
7
:
59
varied with age.
At two weeks of age, Nos. 2,
and 8 had the highest ratios; Nos. 1 and
next in line, followed by Nos.
weeks of age, Nos. 3,
seedlings from Nos. 2,
4
4, 6
9
and 7.
3,5
were
At four
and 8 had the highest ratios;
5,
6 and 9 exhibited the next
highest ratios, while Nos. 1 and 7 had the smallest
ratios.
Seedlings from No. 6 had the largest ratio
at eight weeks of age, followed by seedlings from
Nos. 1, 2, 3,
4,
7 and 9.
Seedlings from No. 8 had
the next smallest ratio according to weight, and
seedlings from No. 5 had the smallest ratio at eight
weeks ot age.
(See Graph 9).
Variation in the length of the photoperiod had
no effect on the length of the cotyledons.
Seedlings
from No. 6 and 7 had the smallest cotyledons, while
seedlings from No. 1 had the longest cotyledons.
Seedlings from Nos. 2, 3,
4, 8
and 9 had cotyledons
slightly smaller than No. 1 seedlings, and No.
5·
seedlings had cotyledons slightly larger than seedlings from Nos. 6 and 7.
(See Graph 10).
The short photoperiod treatment reduced the
grams per centimeter of root length statistics in all
cases, however, this treatment and an increase in age
60
Graph
9
Average root/shoot ratios according to weight
of Douglas fir seedlings from nine seed sources
at two, four and eight weeks of age under long
(dotted bars) and short (solid bars) photoperiodic
conditions.
61
'1
1.2
~
~ 0.9
~
~
Vii
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~
~ 0.6
~
~ 0.3
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~ 12
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~ 12
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Cl 0.9
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5
6
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m
SOURCES
Graph
9
:-..
:·
::
::
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....
7
8
I
9
62
Graph 10
Average cotyledon lengths of Douglas fir
seedlings from nine seed sources at two weeks of
age, grown under long (dotted bars} and short
(solid bars} photoperiods.
Z.7
("t'\
-.{)
2.4
2.1
~
~
I.B
h:
1.5
~
~
\.J
~
~
~
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_,
0
d
1.2
-&tU
H
0
0.9
0.6
0.3
0.0
I
2.
4
5
50tJRCE5
6
7
8
9
64
did not change the ranking of the seed sources appreciably.
Seedlings from No. 8 had the highest weight
per centimeter of root length statistics, but were
closely followed by seedlings from No.
5.
Seedlings
£rom Nos. 2, 3 and 9 were intermediary, while seedlings from Nos. 1 and
4 had
the next smallest weight
per centimeter o£ root length, while seedlings from
Nos. 6 and 7 were the smallest.
(See Graph 11).
The ranking of the seedlings according to resistance to low temperatures and soil drought were the
same.
Age did not a£fect the rankings except at two
weeks, where Nos. 1, 6 and 7 were grouped together,
whereas at £our and eight weeks of age 1 was distinctly different from 6 and 7.
Only in Nos. 1,
4,
6, 7 and 9 did varying photoperiodic treatment affect
amount of resistance exhibited by the seedlings.
Seedlings £rom Nos. 1, 6 and 7, when grown under short
photoperiodic conditions, exhibited a greater resistance to soil drought and low temperatures at both
four and eight weeks of age.
Numbers
4 and
9 seed-
lings grown under short photoperiodic conditions exhibited greater resistance only at eight weeks of age.
In all other instances, more seedlings which were
65
Graph 11
Average weight in grams per centimeter or
root length or Douglas rir seedlings rrom nine
seed sources, grown under long (dotted bars) and
short (solid bars) photoperiods.
66
3.0
Z.5
~ .,.,2.0
~~
~
~
4J
........
~
~~I.S
:
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CX) ""''·
0
0.5
u
~
Q,:
....
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:
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r-:
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::
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~=
..
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....._
~ ~1.5
C:is,_;
Yl~
..
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~ ~/.0
~~
~
~
(.:J
0.5
0
..
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..• .
1--.
I
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C)
(5~1.0
~~
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I
Graph 11
....
_~.
::..
....
rr~·
:~
:.
..
..
"
·:1..
6]
grown under short photoperiods were killed by soil
drought and low temperature treatment than were killed
When the seedlings were grown under long photoperiodic conditions, but statistically there was no significant difference in these figures.
Numbers 6 and 7
seedlings usually had the least number of seedlings
killed by soil drought and cold temperature treatment,
closely followed by No. 1.
Numbers
4
and 9 ranked
just below No. 1 with regards to resistance, with Nos.
2 and 3 next in line.
Seedlings from Nos. 5 and 8
exhibited very little resistance to low temperatures
and soil drought.
(See Graphs 12 and 13).
Seedlings from Montana set buds first when grown
under short photoperiodic conditions, followed by
seedlings from Nos. 7, 1,
4, 3,
2 and 9 in that order.
Seedlings from Nos. 5 and 8 did not set buds during
the course of this experiment.
(See Graph 14.)
No
buds were set under long photoperiods.
Relative Rates
££
Radicle Elongation
And Temperature Relations
In general, temperature treatments did not affect
the ranking of the seed sources with regards to rate of
68
Graph 12
Number of two, four and eight weeks old seedlings from nine Douglas fir seed sources killed by
cold treatment in a sample of thirty seedlings grow.n
under long (dotted bars) and short (solid bars)
photoperiods.
:;
..
::
·:
'•
'•
I
'•
....
..
,•
'•
::
'•
•,
·:
..
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r:-:
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:·
..
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..
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..
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....
..
....
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..:·
0
I
....
2
.·
..
'•
...
.rl
'•
....
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'•
.,
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::
•:
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....
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....
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..
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3
4
•'
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.:·.
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.;
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5
6
SOIJRC£5
Graph 12
..
....
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::..
:·
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I!'
'•
..
..
....
.·:.
..·:
..:.
....
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.•'.
7
8
9
:~
::
'•
'•
·:
'•
,•
70
Graph 13
Number or two, four and eight weeks old Douglas
fir seedlings from nine seed sources killed by soil
drought treatment in a sample of thirty seedlings
grown under long (dotted bars) and short (solid bars)
photoperiods.
71
30
r:'
..
..
..
....
30
..
..
....
..
..
......
..
..
..
..
30
..
..
..
..
..
'
..
..
~
..
..
J
4
r.:
..
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..
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..
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..
5
6
1
..
2
..
..
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....
..
..
....
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r.:
....
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..
..
....
..=:1
::
....
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..
..
SOURCES
Graph
13
..
..
a
9
72
Graph
14
Dates of bud setting of Douglas fir seedlings
from seven seed sources grown under short photoperiodic conditions.
The date of planting was June 17.
Numbers of the points correspond to the seed source
numbers listed in Table one.
73
8
0
...__
~
l(
7
7
b
0
6
~ 5
~
<:::::>
8
.........
0
I
4
~
lt...J 3
0
4
~
"
j::::
......,J
~
2
0
J
I
0
2
0
9
0
5
10
15
20
25
JULY
30
4
9
AUCU5T
DATE
Grap~
14
14
74
seedling radicle elongation.
Seedlings from both late
and early germinating seeds in the cases of Nos. 2, 3,
5 and 8 exhibited approximately equal radicle elongation rates; but, in the cases of seedlings from Nos.
1, 6, 7 and 9, the rate of radicle elongation in seedlings from late germinating seeds was greatly reduced.
When the seedlings came from early germinating
seeds, Nos. 6 and 7 seedlings exhibited extremely rapid
radicle elongation.
These were closely followed by
seedlings from No. 1.
Compared to No. 1, Nos.
4
and 9
showed slightly less rapid radicle elongation in their
seedlings, followed by seedlings from Nos. 2 and 3.
Seedlings from Nos.
5
and 8 exhibited comparatively
slow radicle elongation.
When the seedlings came from early germinating
seeds, seedlings from Nos. 1, 2, 3,
4, 5, 6
and 7 showed
most rapid radicle elongation at 25°c. constant temperature, while radicle elongation was greatest at
30°0. constant temperature in seedlings from No. 8.
Seedlings from No. 9 exhibited most rapid radicle
elongation at the alternating temperatures of 20° and
30°c.
When the seedlings came from late germinating
75
seeds, the optimum temperature conditions ror the
radicle elongation or seedlings rrom Nos. 1, 4, 6
and 7 was still 25°c. constant temperature, but Nos.
2, 3,
5,
8 and 9 seedlings had their most rapid
radicle elongation at the alternating temperatures or
20° and 30°c.
(See Graphs 15 through 21).
Germination And Temperature Relations
At 10°c. only seeds rrom Nos. lA, 2A, )A, 4A
and 5A exhibited any germination, with No. lA having
the most germinated seeds, closely rollowed by Nos.
2A and 3A.
Numbers 4A and 5A had only a slight amount
or germination at this temperature.
At 15°c, seeds rrom No. 4A exhibited the most
germination,
rollow~d
by seeds from Nos. 2A and 5A;
lA and 3A; 9A; 6A; and,7A and 8A, in those groupings
and order respectively.
Under the 20°c. treatment,
the rollowing decreasing order or maximum germination obtained:
and 9A.
4A and 5A; lA, 2A and 3A; 8A; 6A, 7A
While at 25°c. the order or decreasing germ-
ination was as follows:
2A and 3A; 6A and 9A.
4A; 5A and 7A; lA and 8A;
The order of the seed sources
according to decreasing germination at 30°c. was:
76
Graph
15
Average radicle length
o~
Douglas
~ir
seedlings
at 14, 21, 28 and 35 days o~ age, grown at 5°c. ~rom
early (solid bars) and late (dotted bars) germinating
seeds
~rom
nine seed sources.
77
c::::)"-1
C5
~
~
4
~-.J
s:sz
c:::)l...J
~~
0
~Q
~ <::5~ 4
~~~
~>;....._
~oq:;~
~ c::q::)
2
~
0
~<0~
I....JC\J'""')
~
~"-J<:::5~
3""'
4-
~~.......,;
-....,J>-:-....J
~~c:)
QC:l~
~-~
Q::l:::\1""1
2
0
0
I
2
3
4
5
6
50tJRCE5
Graph
15
7
8
9
78
Graph
16
Average radicle length
at
14, 21, 28 and 35 days
~rom
o~
Douglas
~ir
seedlings
o~ age, grown at 10°c.
early (solid bars) and late (dotted bars) germin-
ating seeds
~rom
nine seed sources.
79
......
::
::
....
t
0
t:..
::
....
::
....
..; .
..
..:·
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1:-:
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·:
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·:
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....
1;':
..
....
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........
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,•
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....
6
t'r
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..
..
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..
·.•,
..
..
..:'
•• ....___
....
..
..
.::.
..
....
....
.•
..
....
......
..
I
1!:..
..
..•'
I':':'
....
::
..
......
..:·
::
..
•'
•'
•'
.:.:I.•._ _...-:...;•'1..----.:..:L..-_1<...:.1....-_
....
1..
:·
r.:'
;'•
..
..
•'
7
8
.•'•'.
'•
.. ......__
..
....
•'
..
..
:·
9
80
Graph 17
Average radicle length of Douglas fir seedlings
at 7, 10,
14, 21
and 28 days of age, grow.n at 15°c.
from early (solid bars) and late (dotted bars) germinating seeds from nine seed sources.
r
81
6
'::..
......
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0
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2
.3
.4
~
..
..
......
..
..··.
..•:
·::'•.
.......
:
....
5
6
50tiRCE5
Graph 17
....
•'
'•
:
....
......
..
·:
....
..
~
::
I
......
t..
::
........
•'
......
::....
......
t::.;
....
..
•'
•'
..
....
.·
'·
....
::
7
....
..
::
:;
8
..
..
..
'•
..
..
'•
·:
9
82
Graph 18
Average radicle length of Douglas fir seedlings
at 3,
7, 10 and 14 days of age, grown at 20°C. from
early (solid bars ) and late (dotted bars) germinating
seeds from nine seed sources.
6
4
..
..
....
·:
:·
z
..
0
•:
..
..
....
..
......
....
..
:l
·:
...;
..
6
4
..::..
2
-:
:
..
1--
:
:
..
-:•.
0
..
::
..::
....
..
:
..:
!i..
1:-:
:;
..
..
::::
....
:
ir:
::
:
..
-:
......
....
..
:
..
:•
4
~
·:
:-
::
..··.
..
....
:
TI::
..
......
::
;.
2
3
:
:
::
:~
..
..
.
.
m
0
I
:•
:
4
5
6
50/JRC£5
Graph 18
7
8
9
84
Graph 19 ,
Average radicle length or Douglas rir seedlings
at 3, 7, 10 and 14 days or age, grown at 25°c. rrom
early (solid bars) and late (dotted bars) germinating
seeds rrom nine seed sources.
85
~
..
~
..
..
..
..
..
t:l
..
·:
·.
I!'!
..
....
..
..
::
.;
......
..
::
..
..
..
..
..
•.
..
..
..
..
..
..
0 ~-=··--~=~=~-=··--~··~~~--~::
~
::
::
..
..
1::..
..
....
.:..:......__
......
....
..
~
~
C)
.._J
~ ~
b
~ ~
"
C5 ~
l&.J ~ ::j 4
"J
~ ~~2
....
~
..
....
..
..
..
..
......
0
..
..
....
........
......
1:-;
....
....
..
2
3
4
':....1
......
b
50/JRC£5
Graph
19
7
::
.....
....
5
::.
....
r:-:
·:.
;;
:·
I
r.:..
..
8
9
86
Graph 20
Average radicle length of Douglas fir seedlings
at 3, 7, 10 and
14
days of age, grown at 30°C. from
early (solid bars) and late (dotted bars) germinating
seeds from nine seed sources.
87
6
..
..
..
..
..
'ii
0
....
......
..
....
..
..
..
..
1:-:
..
..
..
I!'.
..
..
~~--.U--~··L-~·~·~~--.W--~~~=:~--=~:~
..
....
....
..
..
~
'•
..
......
..
··~....-
......
..::
..
f:-;
....
....
..::
o~
..
......
..
..
I
..
......
....
2
t:-:
..
..
..
..
....
..
..
:·
'•
;..:j.'._ _ _ _.........,
..
.'•.
..
..
....
..
t;:"
..
..
4
..
..
..
..
f!:::
~
..
..
..'•
....
....
..
I:::-
......
5
G
SOtiRCcS
Graph 20
7
8
9
88
Graph 21
Average radicle length
o~
Douglas
~ir
seedlings
at 3, 7, 10 and 14 days o~ age, grown at 20 and 30°c.
alternating
~rom
early (solid bars) and late (dotted
bars) germinating seeds
~rom
nine seed sources.
..
t::
1:-:-
......
..
..
..
t
..
::-.._
I!'
..
:·
....
....
:·
:·
0 ~
..
..·:..
..
......
..
..
....
t::
..
....
....
......
....
....
..
:·
1;-:
:....~
....
..
....
..
..
..
..
~
......
....
..
..
..
..
......
~
t::
......
...
..
....
..
..
~
.
~
..
..
.:.:.....___
..
..
......
........
....
.::.
I!':
..
I
2
3
4
5
6
SOURCES
Graph 21
8
9
90
9A; 4A and 5A; 2A, 3A and 6A; lA, 7A and 8A.
20 0
-
At the
30 0 c. alternating temperature treatments, the
order or decreasing germination according to numbers
was:
2A, 4A and 9A; 5A; 1A; lA, 3A and 8A; 6A.
Under all temperature treatments, seeds rrom
Nos. lA, 2A and 3A germinated rirst and most rapidly.
Seeds £rom Nos.
4A
and 5A rollowed the three above
numbers with regards to earliness and rapidity or
germination. . Seeds from the other seed sources varied
in their ability to reach maximum germination rapidly
according to the temperature treatment and as a whole
showed no rapid burst or germination.
Seeds from Nos. lA, 3A and 6A exhibited maximum
germination at both the 20°C. and 25°c. temperature
treatments; while the optimum temperature condition
for germination of seeds rrom Nos. 2A and 9A was the
alternating 20
0
0
- 30 c. temperature.
Seeds from Nos.
4A, 5A, 7A and 8A reached max~ germination at 25°c.
(See Graph 22).
General Characteristics 2£ Douglas Fir Seeds
~
Seedlings
Seedlings from seed source one were large, fast
91
Table 5
Results or L.S.D. and Extreme Mean tests according to numbers or seeds germinated at two, rive, seven,
ten, rourteen, twenty-two and twenty-nine days or ten,
rirteen, twenty, twenty-rive, thirty and twenty-thirty
alternating degrees
c.
treatment.
Seed source numbers
correspond to seed sources listed in Table 2.
Table
AGE
'5
T!lll'ERA TURE
10°
c.
1'5" c.
20"
2 DAYS
c.
~
U, 2! 1 )A -
SEEDS TO
u,
21 - ~ SEEDS TO
U, )A )
u,
2A, )A)
4A,
')A,
6A,
u,
31) U, 21, 9A) 4A,
6A,
SA )
J..4
U, 21, )A - ctlLI
7A,
6A
4A,
U, 21, )A,
2A, 3J.)
6A,
7A, 81, 9A
10 DAYS
u,
6A,
')A,)
IIA,
9A
21, )A,
4A,
SA )
7A,
5A,)
4A,
7A,
IIA,
U, 21 1 )A - OIILY
9A)
U, 21, )A,
21,
41.,
7A, 81
6A,
U, 21, )A,
4A,
5A -
29 DAYS
ctlLY SEEDS TO GF.Rl!INATE
9A )
5A )
u,
61, 7A,
U, 21 1 )A,
9A )
6A,
4A,
7A, BA
u,
6A,
u,
31,
U, 21,
4A,
5A )
7A,
IIA, 9A
)A,
')A,
U, 2A 1 ) A,
7A,
4A,
')A )
IIA, 9A
U, 2A, )A,
21,
6A,
U,
U,
U, 21 1 )A,
SA, 7A,
u,
6A,
')A, 9A )
6A
>
4A,
4A,
6A
')A, 7A,
4A,
4A,
9J. )
')A, 9A )
6A,
SA, 9A
>
u,
JJ., 4A, SA, 9A
21,
4A,
U, 21 1 )A,
9A )
U, 2! 1 3J.,
6A
21,
6A
4A,
61, 7A,
4A,
5A,
6A
')A, 9A )
6A) 6A,
U
1
21 1 )A,
9A )
>
6A
6A, 7A,
7A,
7A,
>
SA, 9A
6A
> u, )A, "'· 9A >
4A
6A
6A
6A,
21,
4A,
7A,
6A,7J.,IIA
21, )A, 9A )
U,
21, )A,
6A,
U, 21, )A,
')A )
u,
6A
4A,
7A,
61, 7A )
6A, 6A
61,
21, )A,
4A,
9A )
6A
6A,
"'· 7A,
81
5A, 7A, 9A
U, 21, )A 1
9A )
> 6A,
JJ., 4A, SA, 7A,
21, )A )
6.\ 1
4A,
61,
6A,
SA, 7A,
9A
> 6A,
9A )
7A, 81, 9A
6A
IIA,
21, )A,
91
')A )
')A, 71 1 9J. )
JJ., 4A, ')A
21,
7A,
22 DAYS
S>:EDS TO G!!JllllNATE
u,
9A
4A,
4A,
GERIIINATE
6A,6A
DAYS
SEEDS TO GERIIINA TE
U, 21, )A,
GERMINATE
7 DAYS
U, 2! 1 )A - ONLY SEEOO TO
GE!M:NATE
U, 2! 1 )A - ONLY SEF.DS TO
GERI!INATE
20°- )o0 c.
21 - O!IL! SEEDS TO
)A)
GE!M:NATE
') DAYS
)o0 c.
2'5° c.
4A,
6.\ 1 6A
U
1
)A,
7A
5A, 7A,
93
Graph 22
Relative rates of germination of Douglas fir
seeds from nine seed sources at
2~co c.,
. 0
10°c., 15 c., 20°c.,
30oc. and alternating temperatures of 20 oc.
0
and 30 c.
94
40
IO"C.
r
f_. - . -
. - -1
JO
.-
--
·-
·· -=-\-==-"·
zo
/0
.... --··· .
~
·····
0
50
20°(.
~
...::
-------:-::.- . - ·.=-=-~~- .
.... -- -.-~--:;,·- -· .... ·-·--·-·· .
40
~
~ JO
~
ct:
~
:.::::
__-----=-:-_-:.::::.
-
zo
..
:--,.::==~.-=---
.
•
Q
"'"'
~ 10
~
"'
0
~
.fO
~
Jo·c.
~ 40
/'
JO
_,./
•"
·---·---·'
•'
/0
zo
--
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _6
10
0
5
/0
15
20
25
0
5
/JA'/5
Gr aph 22
/0
15
zo
2.5
95
growing seedlings, with a tall shoot and very long
root systems.
Radicle elongation in seedlings from
early germinating seeds was very rapid, but this
elongation rate was very much reduced in seedlings
from late germinating seeds.
The hypocotyl reddened
at an early date, and the seedlings were very resistant to low temperatures and soil drought.
became dormant at an early date.
Their buds
The seeds exhibited
a high and rapid rate of germination, and they had an
ability to germinate slowly at very low temperatures.
Germination was greatly reduced at high temperatures.
Seedlings from seed sources two and three were
closely allied in most of their morphological characteristics.
On the whole, these seedlings were what
might be called in this experiment "average" seedlings.
They occupied middle positions in regards to almost all
morphological and physiological characteristics.
Their
buds became dormant at a late date, but they did become
dormant.
No seeds were available for germination
studies.
Seedlings from No.
4 closely
approached, but
never quite reached or equaled seedlings from No. 1.
On the other hand, they were usually larger and more
resistant to low temperatures and soil drought than
were seedlings from Nos. 2 and 3.
Their seedling
hypocotyls reddened at a fairly early date; seeds
from this seed source exhibited some germination at
the lowest temperature treatment, but the rate of
germination was never quite as rapid as the rate of
germination of seeds from No. 1.
Numbers
5 and 8 seedlings were also closely
related both morphologically and physiologically.
Particularly was this relation so in the latter case.
Seedlings from these two seed sources were markedly
non-resistant to soil drought and low temperatures and
their root systems were nearly always shortest.
Hypo-
cetyl reddening, if it occurred at all, was very late,
and radicle elongation was very slow at all temperatures.
Buds were never set under short photoperiodic conditions during the extent of this experiment.
No seeds
were available for germination studies.
Seedlings from Nos.
6 and 7 were also usually
comparable both morphologically and physiologically.
They were the most resistant seedlings to soil drought
and low temperatures.
Their seedlings had extremely
long root systems, but their tops, or shoots, were
97
alw~ys
the shortest.
at a very early age.
Hypocotyl reddening occurred
Radicle elongation was extreme-
ly rapid, as was the germination rate
o~
their seeds.
Seedlings ~rom No. 6 set their buds only slightly
earlier than seedlings
~rom
No. 7.
These seedlings
appeared to be extremely susceptible to the strains
o~ damping-o~~ ~ungi ~ound
in the Oregon soil used
in the greenhouse experiments.
Seedlings
~rom
intermediary type
o~
No. 9 appeared to represent an
seedling between those seedlings
£rom No. 1 and seedlings
~rom
Nos.
5 and 8. Top
growth was luxuriant, but the root length was long.
No. 9 seedlings were highly resistant to low temperatures and soil drought, but the date
very late.
o~
bud set was
Radicle elongation was fairly rapid, but
germination was comparatively slow and no germination
occurred at the lowest temperature treatment.
Table 6 gives a general summary
o~
the morpho-
logical and physiological characteristics
~rom
the seed sources listed in Table one.
o~
seedlings
T1BLl
6. J. ._..,. or
SOURCX
tile ollancterUtica ozhibit.d
COTYLIDOII
LI!ICI'II
tiROOf
CIWIACTZRISTICS
b7
the IIOed oo\11'011• Uet.d 1a 'fable - ·
IPICoriL
ELOIIGATICll
at
at
TillE R!QUIRID
R!LATIVJ:
R!LATIVJ:
RADICLI
SHatT
OEIUIIIIA TION
Pt1l lllll SET
LC11 TIIIPZRATURI
SOIL DROOOIIT
!LONOATICll
PIIOTOPERI<Il
CIW!J.CTERISTICS
UNDER SHatT
RI!SISTJ.IICI
RF.SISTJ.ICI
RATI
APPARENT
Otii!J.TE
RF.SPONSI
1.
Jaclaoon.
c-t;T,
aro..,..
2. Pieroo,
c-v. cr.caa
Rapid
LoQ&
r.e
3. llou&lae
eo...v. ar...,..
Lcac
lli&h
ll1&h
llodiua
38 Dqe
llodia
llodia
llodi\8
40
Dqe
llodia
*<11-
30
Dqa
Did lot
v...,- r..
Vfll'T I.-
17~
Vfll'T lli&h
Vfll'T lli&h
19
v...,-
Vel'7
lli&h
Vfll'T
t.
Rapid
Veey High
llldia
llodi\8
Rapid
llldia
Rapid
Rapid
llodia
s1....
v...,- r..
Vfll'T Slclor
Vfll'T Rapid
Vfll'T
llodi,. Lollc
llldia Lane
llodia
*<11- Thiol<
Lane
counv, ar.c-
*<lia Thick
S. Jette.--
Rapid
Sbart
llodi-
C01111t;T• laahiagt.
--
loll CouDt;r
v...,-
Thick
Vfll'T
Lane
Short
s-
v...,-
7 • Pvil: COUDt;y•
Short
Col......,
Vfll'T Good
Vfll'T S].QW
Voq Rapid
v...,-
ll1&h
v...,- Rapid
Dqa
ll1&h
Vfll'T Good
Short
8. l'lllk Coan1;r•
llodia
9. L1all CouDt;r.
Oropa
v...,- IAac
v...,- Th1.a
Rapid
lli&h
Voq Th1a
ar.c-
s...
24~
Rapid
llodia Thick
4. llcNclu
6.
PIIOTOPERICil6
ThiA
v...,. Tbick
Lone
llodi-
llodia Tllick
Rapid
Vfll'T I.-
*<11-
Slclor
*<lia
lli&h
.....
Did Hot
Vfll'T 1'.-
46
111&11
Dqa
• l'lret clooeorlpU• ...,.,.. to tile roelatin 1.eact11 or tile root, whUe tile Moond clooecl"ipti011 ...ton to tile "'latin thiola>e.. or tile root..
-
nr.t
deecl"i~
...,.,.. to tile Nlatin roete or pnd.MUoa, w1111e tile eooond clooecl"ipti.., ...tere to tile _,.,t or ~tion at tile ~et. ~tur.e.
"'o:>
99
DISCUSSION
The data collected in this study clearly show
that seeds and seedlings rrom dirrerent areas possess
more or less distinct morphological and physiological
characteristics.
Presumably, at least some of these
characteristics are rigidly controlled by the genotype.
In some instances, morphological and physio-
logical characters appear to be inter-related, while
in other cases, no correlation is found.
On the basis
of this preliminary study, certain relationships between seed sources are suggested.
However, a much
more critical evaluation of the variation within ' each
geographic area, tested under a variety or conditions
will be necessary berore generalized statements or relationships can be justified.
No correlation
~pears
to exist between the length
of the hypocotyl and physiological reactions.
For in-
stance, seedlings from Colorado and :Montana, which
exhibit the highest resistances to soil drought and low
temperatures, have the shortest hypocotyls, but seedlings from Jackson County, Oregon that closely approach
Colorado and Montana seedlings in resistance to soil
drought and low temperatures, have the longest hypo-
100
cotyls.
However, differences exist in the date of
appearance of a red coloration of the hypocotyl.
Those seedlings which exhibit greatest resistance to
low temperatures and soil drought acquire this red
coloration earliest in their development.
Owen (36)
has noted a reddening of the hypocotyl with increased
resistance to high soil sureace temperatures.
In this
study, the red color appears to be correlated with resistance to soil drought and low temperatures.
Per-
haps the rate of hypocotyl reddening is an indication
of the general hardiness of the seedling.
In con-
junction with the above observation, the hardier seedlings appear to have much thinner hypocotyls.
The longer the hypocotyl, generally speaking, the
longer are the cotyledons.
Other than this relation-
ship, the length of the cotyledons does not appear to
be directly correlated with any other measurement.
One of the morphological characteristics that
show striking differences between seedlings grown
from seeds from different seed sources is the weight
per centimeter of root length.
Seedlings from the
more temperate regions of the species range exhibit
heavy roots in contrast to those seedlings from such
101
areas as Colorado and Montana.
This heaviness appears
to be due primarily to thickness of the root and not
to an increase in branching.
The seedlings with the
heaviest roots sppear to be easiest to break during
removal from the soil; the thinner roots are very
wiry in nature.
Perhaps the thicker roots have a
greater development of parenchyma tissue.
A root such
as this would be relatively easy to break as compared
with a root consisting primarily of stelar tissues.
Since the thicker roots are usually the shorter roots,
perhaps the increase in parenchyma tissue would indicate that more food is being stored and less food being
used in root elongation.
With the exception of Linn
County, Oregon seedlings, which had thick roots, small,
wiry, deeply penetrating roots and resistance to low
temperature and soil drought are positively correlated.
When the
~ot/shoot
ratios of the seedlings
grown under short photoperiods are plotted against age,
instead a rising-falling type of curve as found in the
case of long photoperiodic conditions, a falling-rising
curve is found.
The more rapid the setting of buds
occurs under short photoperiodic conditions, the
steeper is the rising section of the root/shoot ratio
102
curve.
The rising slope of the root/shoot ratio curve
of seedlings grown under short photoperiods is due
not only to a reduction or complete cessation of shoot
growth during the four to eight weeks age increment,
but also in part, to an increase in the rate of root
growth during this period.
(See Graph
4>.
Under long
photoperiod treatment, this situation is reversed.
Perhaps, the photosynthate which would have ordinarily
been used in shoot growth under long photoperiodic conditions is being shunted into use for root growth under
short photoperiodic conditions.
The importance of this
latter possibility to forest nurseries is readily apparent.
If the shoots of the seedlings can be artific-
ially hardened and the shoot growth retarded or stopped
by subjecting the seedlings to short photoperiods, and
at the same time stimulate, or at least maintain, root
growth, a much hardier seedling could be produced for
planting purposes.
The effect of a varying photoperiod on epicotyl
elongation and bud setting has been observed in ecotypes of other tree species (23, 50, 52, 53).
Earli-
ness of bud set with increasing altitude and a shortened growing season is an obvious adaptive feature of the
103
ecotype.
At high altitudes, short growing seasons
are the rule, and timing of growth and optimwn .environmental conditions is very critical.
Frosts occur
early in the fall and early hardening of the shoot
would be essential to survival.
Day lengths shorten
before these frosts occur and seedlings which rapidly
achieve hardiness and cease vegetative shoot growth
under short photoperiodic conditions would have a
definite advantage over seedlings which were comparatively unresponsive to a shortening photoperiod.
However, many instances of interaction between temperature and photoperiod have been noted in ecotypes of
other species (25,
34,
35), and no interpretation of
an apparent photoperiodic response is complete unless
the temperature factor is also taken into account.
Those seed sources with plants producing the longest
roots also show the most rapid radicle elongation at
all temperature treatments, and greatest resistance
to soil drought and low temperature.
Seedlings from lower altitudes show the most
rapid radicle development at alternating temperatures
of 20° and 30°c., While those seedlings from higher
0
provenances grew most rapidly at 25 C.
No ecological
104
explanation can be suggested for this apparent difference in response.
Of special interest is the relation between
radicle elongation of the early and late germinating
seeds from each source.
In those seedlings from the
more rigorous climates, such as Colorado and Montana,
the reduced elongation rate of the seedlings derived
from late germinating seeds is marked.
With seedlings
from the less rigorous climates, such as Polk County,
Oregon, radicle elongation is about equal for seedlings
derived from both late and early germinating seeds.
If such a relationship between early and late developing seeds in certain ecotypes are real, an effort to
screen out the late maturing seeds may be justified
in a direct seeding operation.
The varied rate of
radicle elongation of germinating seeds from various
locations may suggest the strong adaptive nature of
this characteristic.
Of especial interest is the
striking difference in radicle elongation from seed
collected from North and South slopes within the same
general area.
Two striking facts from the studies of seed
germination are to be noted:
(1)
the ability of
seeds from the higher altitudes to germinate at very
105
low temperatures; and, (2) the ability of high altitude seeds to rapidly achieve maximum germination.
Only seeds from the high Rocky Mountain areas,
Colorado and Montana, gave appreciable amounts of
germination at l0°C.
However, a few seeds from the
higher elevation areas of Oregon did germinate at this
temperature.
None of the seeds from the lower alti-
tudes of Washington and Oregon germinated at l0°C.
The seeds from higher altitudes under all temperature conditions exhibit a "flush" of rapid germination and then practically cease to germinate.
In
direct opposition to this pattern, seeds from lower
altitudes continue to germinate over longer periods of
time.
The total percentage of seeds germinating is
usually greater in high elevation seed lots.
A clinal development of ecotypic seedling
characteristics correlated with elevation appears to
exist in seedlings from the Oregon counties of Jackson,
Douglas, and Polk.
From elevations of 4500, 3500,
1500 and 500 feet respectively.
They show a continuous
decline in ability to grow roots rapidly, in rates of
radicle elongation, in rapidity of germination, in
ability to germinate at low temperatures and in
106
resistance to soil drought and low temperatures.
Perhaps studies in the future will further outline
and delineate other clines of ecotype development
throughout the range of Douglas fir.
In all characters, seedlings from Montana and
Colorado exhibit a high degree of adaptation to the
comparatively rigorous environment of the Douglas fir
region in the Rocky Mountains.
Rapid root and radicle
growth, small, short shoots and cotyledons, extremely
rapid germination and ability to germinate under low
temperature conditions, very high resistance to soil
drought and low temperatures are characteristics of
seedlings.
Seedlings from Montana and Colorado are generally
comparable, but some differences were observed.
For
instance, Montana seedlings set their buds sooner than
do Colorado seedlings; root/shoot ratios tend to be
larger in Montana seedlings and germination rates are
slightly higher in Montana seed lots.
In the latter
case, the data also show differences between seeds
from north and south slopes in Montana.
The north
slope seeds give slightly more rapid and complete
germination than do seeds from the south slopes.
107
Characteristics of seedlings grown from seeds
from Douglas County, Oregon (No. 3) often correspond
to the seedling characteristics of seedlings from
Pierce County, Washington, even though the latter seed
source is three to four degrees of latitude to the
north.
The relative effects of latitude as compared
to the many other features of the environment such as
aspect, soils, etc. cannot be evaluated without more
complete data on the seed collection sites.
from Nos.
Seedlings
5 and 8, Jefferson County, Washington and
Polk County, Oregon may be compounded in a similar
manner.
In contrast, seedlings from No. 8 and No. 9
located in Polk and Linn Counties, Oregon, respectively, are of similar latitude and elevation.
Yet,
their seedling characteristics are extremely different.
Linn County seedlings are much more frost and soil
drought resistant.
Linn County seedlings, as a rule,
have much deeper root systems and exhibit more rapid
radicle development than do seedlings from Polk County.
An explanation may lie in the fact that No. 8 is in
the Coast Range in one of the more moist regions of
the species range, and a large amount of the area is
108
classified as Site I for Douglas fir growth, whereas
No. 9 lies on the western base of the Cascade mountains close to the Willamette valley in a much drier
area, classified as Site III or IV.
Number 9 seed-
lings are even more resistant to low temperatures
and soil drought than seedlings from Nos. 2 and 3
which come from higher elevations.
Altitude and
latitude alone may not delimit ecotypes.
The causes
behind ecotype differentiation are related to the
whole environment including climate, soil and biotic
factors.
Certain seedling morphological characters stand
out as reflections of physiological "toughness" of
the seedling:
(1)
seedlings whose roots have low
weight per length figures are tougher than seedlings
with the reverse situation;
(2)
seedlings with
high root/shoot ratios according to length exhibit
greater physiological resistance;
(3) seeds exhi-
biting rapid germination rates usually produce more
resistant seedlings;
<4>
rapid radicle elongation is
closely associated with physiological resistance; and,
(5) early bud setting under short photoperiodic treatment usually indicates a more resistant seedling.
109
Generalized interpretation
the data
o~
~rom
this study are limited by certain handicaps.
tially these are related to the problem
in this type
o~
preliminary study.
sampling
o~
Seeds
Essen-
~rom
known
parent trees would have been invaluable, and a more
thorough knowledge
o~
the sites in which the seed
trees were located would have been
greater number
ways:
(1)
o~
pre~erred.
A
seeds could have been used in several
to give more replication within the experi-
ments; (2)
to allow the experiments to be duplicated
one or more times; and, (3) to give enough seeds to
allow
~or
screening
~or uni~orm
weight and size.
However, the work does suggest possible leads
~urther
o~
study.
seedlings
This may include:
~rom di~~erent
(1)
the
~or
per~ormance
seed sources as they grow
older and are subjected to varied environments; (2)
reciprocal transplant experiments; (3)
o~
the correlation
seed and seedling characteristics with microclimatic
data
o~
the seed sources; (4)
possible correlations
characters; (5)
o~
~urther
investigation
o~
morphological and physiological
the correlation
o~
seedling and mature
tree characteristics; and, (6) above all else, a basic
llO
study of the genetics and inheritance pattern of
ecotypic characteristics ot Douglas fir.
111
SUMMARY
This research was conducted in such a manner as to
further recognition of ecotypes of Douglas fir in the
juvenile stage and determine criteria at this stage of
development which might be used to delineate genotypic
variation within the species.
To achieve these objectives, Douglas fir seedlings
were grown under greenhouse conditions from seeds secured
from areas covering a wide range of altitude and latitude.
To further differentiate these seedlings, a long and
short photoperiod treatment was used.
Comparative morpho-
logical data was obtained from the seedlings at two, four
and eight weeks of age.
This data consisted of cotyledon
lengths, hypocotyl lengths, root lengths, epicotyl elongation, oven-dry weights of the roots and shoots, grams
per centimeter of root length, root/shoot ratios according
to both weight and length, relative earliness of bud set
under the short photoperiod treatment and earliness of
hypocotyl reddening.
In addition, seedlings grown in the
greenhouse under the long and short photoperiod treatments
were tested for resistance to soil drought and low temperatures.
Relative rates of germination and radicle elong-
ation were determined at several controlled temperatures.
Distinct differences, both morphological and
physiological, were noticed between seeds and seedlings
112
from the seed sources at the altitudinal extremes. Those
seedlings from the higher altitudes of Oregon, as compared
with those from the lower altitudes, exhibited much deeper
root systems; higher root/shoot ratios according to length;
comparatively more rapid radicle elongation at both low
and intermediate temperatures; and, the hypocotyls reddened at an earlier age.
These high altitude seedlings
were much more resistant to soil drought and low temperatures than those seedlings from the lower altitudes.
The
high altitude seeds bad a comparatively more rapid germination rate, and germinated at lower temperatures than did
the low altitude seeds.
Under the short photoperiod treatment, the high
altitude seedlings set their buds at an earlier date than
did the low altitude seedlings.
Also, the short photoperiod
treatment failed to increase the resistance of the low
altitude seedlings to soil drought and low temperatures,
whereas the resistance of the high altitude seedlings was
increased by the short photoperiod treatment.
The falling-
rising pattern of the curve noted when the short photoperiod
root/shoot ratios according to length were plotted against
age was much more marked in the high altitude seedlings.
The seedlings from the intermediate altitudes were
similar to each other in many respects.
differences were observed.
However, some
In general, the root/shoot
113
ratios according to length, the germination rates and the
rates of radicle elongation decreased gradually with a
decrease in altitude of the seed sources.
The date of bud setting of the seedlings from the
~
seed sources of the intermediate altitudes gradually '
increased with a decrease in altitude, and the ability of
the short photoperiod treatment to increase resistance to
soil drought and low temperatures progressively decreased
with a decrease in elevation.
Distinct differences were found to exist between
characteristics of the coast seeds and seedlings and the
characteristics of the seeds and seedlings from the Rooky
Mountain areas.
For instance, the Rooky Mountain seedlings,
as compared with the coastal seedlings, had smaller, more
compact shoots; much smaller cotyledons; deeper, more
rapidly elongating radicles and roots; more rapid and
complete germination; greater resistance to soil drought
and low temperatures; and, a more rapid and complete
response to the short photoperiod treatment in every
respect.
The seeds and seedlings from the two Rooky Mountain
seed sources were similar in many respects, but some
differences were noted.
The Montana seedlings had a
slightly higher root/shoot ratio according to weight and
set their buds at earlier dates than did the Colorado
114
seedlings when exposed to the short photoperiod treatment.
Montana seeds exhibited a more rapid rate of
germination than did the Colorado seeds; this was
particularly so when the Montana seeds came from a
north slope site.
Distinct differences existed between the seedlings
from Polk County and Linn county, oregon.
These areas
are similar in elevation and latitude, but differ
-markedly in annual precipitation.
In practically all
cases of comparison, the seedlings from Linn County
exhibited an apparent adaptation to the drier environment; i.e., longer roots; a larger root/shoot ratio
according to length; a comparatively more rapid rate
of radicle elongation; and, a greater resistance to
soil drought and low temperatures.
In many cases, the
seedlings from Linn County closely approached or
equalled morphologically and physiologically the
seedlings from the higher altitudes of Oregon.
In all seeds and seedlings from the higher altitudes
and drier seed sources, a distinctly narrower range of
variation was found as compared with the variation of
the seeds and seedlings from the lower and wetter areas.
In addition to this uniformity, certain other characteristics were possessed in common: the germination was
115
rapid and complete; the rate of radicle elongation and
root growth was relatively rapid; the roots were thin
and wiry; the root/shoot ratio according to length
was comparatively high; the resistance to soil drought
and low temperatures was relatively high; and, the
hypoeotyls reddened at an early age.
116
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