127
Notes
"White Seedling": A Pigment Mutation
That Affects Seed Dormancy
in Douglas-fir
FnANK
C.
SoRENSEN
T
HIS note describes a chlorophyll-less mutant
of Douglas-fir and its association with speed
of germination. Hecessive chlorophyll mutants
have been frequently observed in plant species (e.g.,
Gustafsson 5 with regard to forest trees). In maize,
it has been observed that the lack of pigmentation
often has been aecompanied by premature germina­
tion or absence of dormancy 14 • There appear to
have been no observations linking lack of chlorophyll
or carotenoids with germination characteristics in
other species, however. This may be because the
traits are not assoeiated in most other speeies,
or because it is diffieult, at least in many plants, to
distinguish the albino from the normal seedling at
the onset of germination, and the association has
The author is principal plant geneticist, Forestry Sciences
I,aboratory, Pacific Northwest Forest and Range Experiment
Station, Forest Service, U. S. Department of Agriculture,
Corvallis, Ore~on 97330.
Summary
Data were collected from 193 pairs of twins on
their tongue rolling ability. This sample population
included 61 pairs of monozygous twins. The data
were then analyzed for concordance and discordance
among monozygous and dizygous twin pairs by
the chi-square method. It was found that the data
were inconsistent with the hypothesis of chance
fluctuation and that the ability to roll the tongue is
strongly influenced by hereditary factors. The data
further indicated a lack of penetrance of 5.75
percent using the entire population sample, and
2.8 percent if the doubtful group (19 individuals
exhibiting intermediate expression) was eliminated.
This lack of penetrance may be due to either heredi­
tary factors or to environmental factors such as a
learning component.
Literature Cited
1. MATLOCK, PHILIP. Identical twins discordant in tongue­
rolling. J. Hered. 43:24. 1952.
2. STURTEVANT, A. H. A new inherited character in man.
Proc. Nat. Acad. Sci. 26:10Q-102. 1940.
3.
. A History of Genetics. Harper and Row,
New York. p. 127. 1965.
been missed. In the present case, germinating white
seedlings could be distinguished from their normal
siblings at the time the radicle was first visible,
which made the relationship between albinism
and speed of germination readily apparent.
Materials and Methods
Two trees, designated in our laboratory as Lac-2
and XWC-8, growing about 30 miles apart in the
Willamette Valley of western Oregon and which
previously had been identified as carriers of the
same recessive white seedling gene, were self- and
reciprocally cross-pollinated in the spring of 1968.
Seeds were collected in the fall, and germination
tests were made in the next winter and spring.
Test seeds were those containing white seedling
embryos. Control seeds were from the same progeny
and contained normal embryos.
Initially, germination tests were made under our
standard conditions for Douglas-fir of 16- to 20-hour
water soak at room temperature, 2-week stratifi­
cation at .5° C, and germination at 30° C day and
20° C night temperatures with 12-hour photo- and
thermoperiods. ::iubsequently, some samples of
seeds were germinated without stratification and
with stratification at 0.5° C and 7.5° C. The purpose
of 0.5° C temperature was to provide stratification
at a temperature at which little or no embryo
elongation would be likely to occur. Purpose of the
7.5° C temperature \vas to stratify at a temperature
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numbers 102, :30, 54, and 7) is 3.45, and less than
7 percent of similar twin samples would yield
proportional differences as great or greater than
that observed were tongue rolling ability not in
fact influenced by hereditary factors. The data are
inconsistent, therefore, with the hypothesis of
chance fluctuations, and we conclude that hereditary
factors strongly influence tongue rolling ability
(P < 0.07).
The fact that only 88.:) percent of monozygous
twin pairs are concordant would indicate .5. 75
percent (half of 11.5 percent) lack of penetrance.
This frequency might be due to either hereditary
factors or environmental factors such as the learning
component previously mentioned.
An even stronger case for genetic influence is
exhibited when the twins in the third group­
parenthesized in Table I -are eliminated from
the analysis. The numbers in Table I then become
96, 24, .51, and :3 with a chi-square of .5.97. Now
P < 0.025, and 94.4 percent of the monozygous
twin pairs are concordant, with 2.8 percent of these
subjects exhibiting a lack of penetrance.
128
The .Journal of Heredity
0.5° C. Normal seedlings responded to stratification
by germinating more rapidly with stratification
than without. \Vhite seedlings, on the other hand,
germinated at about the same rate with or without
stratification. A similar comparison can be made
between Lac-2 X XWC-8 seed lots that were strati­
fied the same length of time (14 days) but at .5° C
and 7 ..5° C. Normal seedlings responded to lower
stratification by germinating more rapidly after
stratification at .5° C than after stratification at
7..5° C. Seeds containing mutant embryos "re­
sponded" to the higher stratification temperature
by germinating in stratification. That these seeds
germinated more rapidly when stratified at 7..5° C
than at 5° C, and normal seeds did not, indicates
that the former lacked a chilling requirement and,
instead, simply responded to higher temperature
with more rapid elongation of the embryo.
Results
Description of mutant
The white seedlings, when allowed to develop in
the light, had neither green nor yellow pigmentation.
However, if the seedcoat was removed prematurely,
the freshly exposed portions of the cotyledons of
many seedlings showed varying intensities of green,
from pale to quite dark . (.3ome germinant seedlings
were without green pigmentation even in freshly
exposed portions of the cotyledons. Proportion of
seedlings showing green coloration under the seed­
coat was not determined.) Green color faded after
a few hours exposure to light. Yellow pigment was
not noticeable in either the portion that had been
exposed to light or the portion that had been pro­
tected from the light. The white seedlings developed
until seedcoat was shed or nearly shed. At this point
the cotyledons started to wither, and the entire
seedling withered within a to 7 days.
Discussion
Occun·ence of the mutant
Although lack of pigment and lack of dormancy
would seem to be a peculiar combination of ehamc­
ters, the combination may be quite frequent. The
phenotype was apparently first reported in maize
where the absence of seed dormancy aspect was
stressed under such names as "germinating seeds" 10,
"primitive sporophyte" 3, "premature germination" 11 ,
and "viviparous"4• Hecently, the combination of
traits also has been observed in western white
pine (personal communication, R. T. Bingham,
Forestry Sciences Laboratory, Forest Service, U. S.
Department of Agriculture, Moscow, Idaho 83843)
and in ponderosa pine (Sorensen, unpublished) .
Lack of pigment and lack of dormancy require­
ments are not always associated. :i\[any albino
mutants have been reported in maizc2 • '-~; however,
it is only those that are also associated with white
or pale yellow endosperm that show vivipary 15 •
But even among these, not all are viviparous.
Germination tests
Table I, which gives results of germination tests,
shows that seeds yielding white seedlings germinate
much more rapidly than normal siblings. Rapid
germination of white seedlings occurred with or
without stratification; in fact, it even occurred in
stratification when the stratification temperature was
a little higher than normal. In addition to more
-rapid germination regardless of pretreatment, the
results also indicate that the seeds containing "white
embryos" lack the response to moist chilling that
most Douglas-fir seeds seem to show.
The more rapid germination characteristic can
be seen in all the tests, but is perhaps best illustrated
by the Lac-2 and XWC-8 seeds that were stratified
at 0 ..5° C. At this temperature, little or no embryo
elongation can be expected during stratification.
The fact that the mutants germinated more rapidly
under these conditions shows that the white embryo
grew faster at the germination temperature.
The lack of response to moist chilling (i.e., Jack of
dormancy) by the mutant embryos is best seen by
comparing seed lots for Lac-2 X XWC-8, which
were unstratified, with those that were stratified at
Table I. Germination of white and nonnal green seed­
lings from se,·eral segregating Douglas-fir families
Stratification
Family
XWC-8 X self
Lac-2 X self
X WC-8 X Lac-2
Lac-2 X X WC-8
Lac-2 X XWC-8
Lac-2 X XWC-8
Lac-2 X XWC-8
Lac-2 X X WC-8
Length
TemperWhite
ature seedlings
Days
oc
14
14
14
14
14
5
5
5
5
7.5
0
15
29
Days to
germination•
.5
.5
2.63.5
1.4
1.5
.2t
4.4
4. 5
3.7
Normal
seedlings
5.4
8.3
4.6
9.2
11.4
16.5
9.0
8.0
• Average number of days to germination of all seeds
which germinated. Test was considered complete when 2
days passed with no new germination. Day on which seeds
went into germination was called 0.
t Of 29 white seedlings, 27 germinated while seeds were
in stratification, but on the day called o-hence, days to
germination less than one.
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that was known to be above optimal for Douglas-fir.
Seeds were checked each day for new germination.
A seed was tallied as germinated when any of the
radicle could be seen. White seedlings could be
distinguished at this time, but all germinated seeds
were still held for a few days to make sure of cor­
rect identification. Germination proceeded rapidly
for these lots and a germination test was con­
sidered complete when two days passed without
any seeds germinating. Germination was, in most
cases, 9.5 to 100 percent complete at this time.
Rate of germination is expressed by simply
determining the average number of days from the
time a sample of seeds enters the germinator until
germination is completed. For example, if one seed
germinated in 8 days, a second seed in 9 days, and a
third in 11 days, the average number of days to
germination for the three seeds would be 9.3.
129
Notes
conditions are right, especially in the absence of
dormancy-breaking treatments. They are similar
only in that in both cases an aspect of dormancy is
involved and control is in the embryo.
Comparative description of mutant
Among albino-viviparous or albino-rapid germi­
nating mutants in maize and conifers, the pigment
phenotypes are remarkably similar. In general,
the mutant seedlings are white, lacking both chloro­
phylls and carotenoids. iVIany of the Douglas-fir
white seedlings have some green color until the
colored tissue is exposed to light, but it then bleaches
out. Similarly, maize viviparous-albino mutants
are green or tinged with green when germinated
in the dark or in dim lighV 7 but bleach in the light.
Western white pine mutants are described as pink
albino (personal communication, R. T. Bingham);
ponderosa pine mutants are pink albino or white.
Pink albino seedlings are known in corn, and they
are viviparous (personal communication, D. S.
Robertson, Iowa State University, Ames 50012).
In maize, vivipary is also associated with white or
pale yellow rather than yellow endosperm. However,
there is no comparable pigmented tissue in the
conifers.
Examination of several albino maize mutants
reveals that they produce protochlorophyllide and
protochlorophyll during germination and growth
in the dark and convert these pigments into chloro­
phyll and chlorophyllide in the lighV 7 • Chlorophyll
production is normal or nearly so; but carotenoids
are reduced or absent, and all mutants bleach with
continued illumination 1 • 16 • Levels of chlorophyll
and carotenoid production are not known for
Douglas-fir, except that some chlorophyll is fre­
quently formed, that it is rapidly bleached in the
light, and that yellow carotenoid pigmentation is
not apparent.
It is more difficult to compare the dormancy
phenotypes because of differences between conifers
and maize, both in the expression of the mutant
and in reproductive behavior. Two points in particu­
lar should be mentioned.
In maize, seeds are produced from double fertili­
zation. Therefore, both the embryo and the nutri­
tive endosperm tissue contain sets of paternal
chromosomes. Dormancy control could be in the
endosperm or in the embryo. However, Hobertson 13
produced single maize seeds with different genetic
constitutions in the embryo and endosperm and
showed that the viviparous allele affected dormancy
through the embryo only. In conifers, the nutrient
tissue for the embryo is the female gametophyte,
which is maternal. Since green and white full
siblings germinate at different times, dormancy
control here also must be in the embryo.
A second possible point of difference is that vivi­
parous maize and other grains 18 • 19 are characterized
by continuous development of the sporophyte
that concludes with sprouting in the ear. In Douglas­
fir, the development of the mutant embryos is not
continuous but only more rapid when germination
One gene or two
The first impression in maize was that there was a
physiological connection between premature germi­
nation and formation of chlorophyll 11 • It appeared
_that single genes with pleiotropic effects were
responsible for the two traits appearing together.
Recombination has been observed\ but this could
be the result of heterofertilization rather than
recombination 14 • Also, there are some "viviparous"
loci not associated with albinism, and vice versa 12 • 14 •
In Douglas-fir data presented above, the white
seedlings have averaged more rapid germin~tion
than have the seeds yielding normal seedlmgs.
However, there is some overlap in the two classes.
A small percentage of green seedlings in almost
every germination test appears before the appearance
of the last white seedling. This is probably chance
distribution of the classes, but it could indicate
that some of the green seedlings are carrying the
allele for rapid germination and some of the white
seedlings are not-that there has been some recombi­
nation between the two classes.
Several white pine carrying the same gene for
white seedlings have been identified (personal com­
munication, R. T. Bingham). In the majority of
the progenies from these trees, seeds containing
normal and white embryos germinated contempo­
raneously. But in the selfed progeny of one tree,
and perhaps another, seed with white embryos
germinated more rapidly or with less stratification
than did seeds with green embryos. This could be
interpreted as evidence for separate genes. However,
subtle environmental differences in cone and seed
handling, or in germination conditions, could pro­
duce the same result, particularly if the albino­
rapid germinating mutants were exceptionally sensi­
tive to drying and wetting conditions (personal
communication, D. S. Hobertson).
Conclusion
The genetic association between pigment pro­
duction and a dormancy control mechanism may be
rather widespread in the plant world. There is
evidence that the association may sometimes be
due to linkage. Usually, however, it appears to be
due to a single gene, or to linkage that must be
very tight. In either case, the fact that the effects
have been located together in Douglas-fir, pine, and
at several points in the maize genome indicates that
some basic relationship between the dormancy
mechanism and pigment formation exists.
Eyster4 remarked that continuous development
of white sporophytes was strongly influenced by
environmental factors, especially moisture. In
fact, he was able to induce dormancy or delay
germination by prematurely drying the ear. Varis
and Manneri 18 also reported that sprouting in the
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Robertson 15 found that 7 of 13 such mutants never
exhibited premature germination. Also, Eyster',
l\1angelsdorf11 , and Robertson 14 have described
viviparous mutants that are not albino.
The .Journal of Heredity
130
ear by green kernels of VIVIparous races of winter
wheat was related to water retention. We have ob­
served only that white Douglas-fir seedlings are
extremely turgid, the cotyledons being almost hard
in the presence of very little structural tissue. If
physiological work is done on the action of this
mutant in the dormancy process, perhaps a good
place to start would be with the water relations of
the germinating seed.
I. ANDEHSON, I. C. and D. S. RoBEHTSON. Role of caro­
tenoid~
in protecting chlorophyll from photodestruction.
Plant Physio/. 35:531-534. 1960.
2. DEMEREC, M. Inheritance of white seedlings in maize.
Gene/i(S 8:561-593. 1923.
3. EYSTER, W. H. A primitive sporophyte in maize. Am. J.
Botany 11:7-14. 1924.
4. - - - - . Vivipary in maize. Genetics 16:574-590. 1931.
Inheritance Of a Dwarf Character
in Sericea Lespedeza
.J. D.
~fiLLER
AND E. D. DoNNELLY
S
EIUCEA, Lespedeza cuneata (Dumont) G. Don,
has been used for many years as a forage and
soil-conserving crop. This study reports the in­
heritance of a dwarf internode character that was
discovered in selfed progeny of an irradiation­
induced sericea mutant.
Hanson and Cope2 reported inheritance of a
The authors are research associate (now research geneti­
cist, Crops Research Division, ARS, USDA, Canal Point,
Florida 33438), and professor, Department of Agronomy
and Soils, Auburn University Agricultural Experiment
Station, Auburn, Alabama 36830. Contribution from the
Department of Agronomy and Soils, Auburn University
Agricultural Experiment Station. Data were taken from a
thesi~ submitted by the senior author to Auburn Universitv
in partial fulfillment of the requirements for the Ph.D. degree.
Downloaded from http://jhered.oxfordjournals.org/ at DigiTop USDA's Digital Desktop Library on January 26, 2015
Summary
A white seedling mutant in Douglas-fir and its
association with speed of germination are described.
Mutant seedlings appeared to lack all carotenoid
pigment; green pigment, though initially present in
some germinant seedlings, bleached rapidly in the
light. Comparisons of seed lots after exposure to
several combinations of stratification temperatures
and periods showed that seeds containing mutant
embryos apparently lacked any stratification (moist
chilling) requirement and germinated more rapidly
than their nonmutant siblings. Union of white
albino or pink albino seedling trait and vivipary, or
rapid germination, also has been reported several
times in maize and in western white and ponderosa
pines.
Literature Cited
5. GusTAFSSON, A. Polyploidy and mutagenesis in forest­
tree breeding. Proc. Fifth World Forest. Congr. 1960, Seattle.
vol. 2, pp. 793-805. 1962.
6. LINDSTROM, E. W. Chlorophyll inheritance in maize.
Cornell Univ. A gr. Exp. Sta. Memoir 13. 68 pp. 1918.
7.
. Concerning the inheritance of green and yellow
pigments in maize seedlings. Genetics 6:91-110. 1921.
8.
. Complementary genes for chlorophyll development in maize and their linkage relations. Genetics 9:305-326.
1924.
9. - - - - . Genetic factors for yellow pigment in maize
and their linkage relations. Genetics 10:442-455. 1925.
10. MANGELSDORF, P. C. The inheritance of defective seeds
in maize.J. Hered. 14:119-125. 1923.
11.
. The genetics and morphology of some
endosperm characters in maize. Conn. Exp. Sta. Bull. 279:
''
513-614. 1926.
12. NEUFER, M. G., L. JoNES, and M. S. ZunEH. The
Mutants of Maize. Crop Sci. Soc. Amer., Madison, Wis. 1968.
13. ROBERTSON, D. S. The genotype of the endosperm and
embryo as it influences vivipary in maize. Proc. Nat. Acad.
Sci. 38:580-583. 1952.
14.
. The genetics of vivipary in maize. Genetics
40:745-760. 1955.
15.
. Linkage studies on mutants in maize with
pigment deficiencies in endosperm and seedling. Genetics
46:649-662. 1961.
16.
, M. D. BACH~LINN, and I. C. ANDERSON.
Role of carotenoids in protecting chlorophyll from photo­
destruction. II. Studies on the effect of four modifiers of the
albino c/1 mutant of maize. Photochem. Photobiol. 5:797-805.
1966.
17. SMITH, J. H. C., L. J. DunHAM, and C. F. \VuRSTEH.
Formation and bleaching of chlorophyll in albino corn
seedlings. Plant Physio/. 34:340-345. 1959.
18. VAms, E. and M. MANNEHI. The effect of the morpho­
logical properties of the ear on the susceptibility of wmter
wheat to sprouting in the ear. M aataloust A ikakausk. 35:
27-35. 1963. (Plant Breed. Abstr. 35: #4021. 1965).
19. YAMAMOTO, K. Investigations on" viviparous" germina­
tion of seed in barley varieties in Japan. Rep. Ins/. A yr. lles.
1'ohoku Um"v. 3:13-27. 1951.
dwarf mutation in serieea that was characterized
by shortened internodes, small leaves, and light
green color. This trait was conditioned by a single
recessive gene. A second dwarf mutation in sericea
was reported 1 that had longer and fewer internodes
but attained a height of not more than 1.5 em. It
-----<'lO·-------_.'lO·---
FIGURE 1-Dwarf plant (left) and normal stature
plant (right) within selfed progeny of X, 18-4.