The response of winter wheat coleoptiles to light of narrow spectral regions
by Bruce Alexander McCallum
A THESIS Submitted to the Graduate Faculty in partial fulfillment of the requirements for the degree
of Master of Science in Agronomy
Montana State University
© Copyright by Bruce Alexander McCallum (1960)
Abstract:
Karmont winter wheat seedlings were germinated for four and five days and exposed to a spectral
range from 4175 Angstroms' to 6400 Angstroms for one, two and three days for each germination
period at growing temperatures of 68° F. and 45° F. Exposure to the spectrum resulted in a retardation
in coleoptile elongation for all wavelengths studied. Wavelength, pre-irradiation germination time and
exposure time main effects and their resulting interaction, with the exception of the pre-irradiation
germination time x exposure time interaction for the 68° F growing temperature, were significant at the
one percent level for both temperatures. THE RESPONSE 0£ WINTER WHEAT COLEOPTILES TO LIGHT
OF NARROW SPECTRAL REGIONS
by
BRUCE A. .McCALLUM
1/
A THESIS
Subm itted to th e Graduate F a c u lty
in
p a r t ia l f u l f i l l m e n t o f th e req u irem en ts
fo r th e d eg ree o f
M aster o f S c ie n c e in Agronomy
at
Montana S t a t e C o lle g e
Approved!
Bozeman, Montana
May, 1960
I
3
ACKNOWLEDGEMENT
The author w ish e s to thank Dr. Ei R.' Hehn fo r h is a d v ic e ,
c o n s tr u c tiv e c r i t i c i s m , and encouragem ent throughout th e co u rse o f
t h i s stu d y .
The au th or a ls o w ish e s to thank Dr. R. V. Wiegand fofc mounting
and a lig n in g th e o p t ic a l system In th e sp ectrograp h and fo r v a lu a b le
a s s i s t a n c e in c l a r i f i c a t i o n o f the' p h y s ic a l a s p e c ts o f th e stu d y ,
and to thank Dr. C. J . Mode fo r h is a id in th e s t a t i s t i c a l a n a ly se s
o f th e stu d y .
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TABLE OF CONTENTS
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ACKNOWLEDGEMENT . . .
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TABLE OF CONTENTS . .
LIST OF TABLES . . . .
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LISTfiOFi FIGURESI i-.;*
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ABSTRACT . . ...................
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9
INTRODUCTION
.
REViIEWVOF LITERATURE ..
17
MATERIALS'rAND METHODS
. . .
RESULTS' . . . . . . .
DISCUSSION . . . . . .
SUMMARY . . . . . .■ .
LITERATURE CITED . . ,
11
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LIST OF TABLES
Page
T ab le I .
T ab le I I .
T ab le I I I .
T ab le IV.
T ab le V>
A n a ly sis o f v a ria n c e f o r th e re sp o n se o f Karmont
w in te r w heat c o l e o p t i l e s to w a v ele n g th , p r e i r r a d i a t i o n g e rm in a tio n time, and exposure a t a
g e rm in a tin g te m p e ra tu re o f 45° F . . . ...............................
23
D iffe re n c e s betw een means o f e f f e c t s and
i n t e r a c t i o n s n e c e s s a ry f o r s ig n if ic a n c e u s in g
S ch eff 6*s method o f .m u l tip le c o m p a r i s o n s , ......................
24
Average c o l e o p t i l e le n g th s , o f Karmoht w in te r
w heat f o r th e main e f f e c t s , w a v e le n g th s, p r e ­
i r r a d i a t i o n g e rm in a tio n tim e and exposure tim e
and th e w avelength x p r e - i r r a d i a t i o n .g e rm in a tio n
and w av elen g th x exposure tim e i n t e r a c t i o n s a t
th e 45° F . And 68° F . grow ing te m p e ra tu re s . . . . . .
25
Average c o l e o p t i l e le n g th s o f Karmont w in te r
' w heat f o r th e ■p r e - i r r a d i a t i o n g e rm in a tio n tim e
x exposure tim e i n t e r a c t i o n a t th e 45° F, and
68° F . grow ing te m p e ra tu re s ............................... ....
A n a ly sis o f v a ria n c e f o r th e re sp o n se < o f Karmont
W in ter w heat c o l e o p t i l e s to .w a v e le n g th , p r e i r r a d i a t i o n tim e and exposure tim e a t a grow ing
te m p e ra tu re o f 68° F,
i . .
29
.
31
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LIST OF FIGURES
Page
F ig u re I .
F ig u re 2 .
F ig u re 3,
F ig u re 4 .
F ig u re 5.
F ig u re 6 .
The l o c a t i o n o f th e s p e c t r a l re g io h s f o r each
box i n th e sp e c to g ra p h a t a f o c a l d is ta n c e o f
®^§^t f e e t e e t o o o e
e e e o o n e o ' i l . e e
C o le o p tile le n g th s a t v a rio u s p la n tin g d e p th s
u n d er c o n d itio n s o f norm al d a y lig h t and d a rk ­
n e s s , o f see d lin g s, grown i n th e g reen h o u se.
c
e
i
i
i
18
e
.
22
A verage c o l e o p t i l e le n g th s o f Karmont w in te r
w heat s e e d lin g s a t th e d i f f e r e n t w avelengths
when grown exposed to o n e, two and th r e e days
o f c o n tin u o u s i r r a d i a t i o n a t th e growing
te m p e ra tu re o f 45° F. The c o l e o p t i l e le n g th
v a lu e s a r e an av erag e o f th e th r e e p r e - "
i r r a d i a t i o n g e rm in a tio n tr e a tm e n ts . , . „ . ........................
27
Average c o l e o p t i l e le n g th s o f Karmont w in te r
w heat s e e d lin g s a t th e d i f f e r e n t w avelengths
when g erm in ated f o r t h r e e , f o u r , and f iv e
days p r i o r to i r r a d i a t i o n a t t ho growing
te m p e ra tu re o f 45° F . The c o l e o p t i l e le n g th
v a lu e s a r e ah av erag e o f th e th r e e l i g h t
le v e ls .
.28
.
A verage c o l e o p t i l e le n g th s o f Karmont w in te r
w heat s e e d lin g s a t th e d i f f e r e n t w avelengths
when exposed to o n e, two and th r e e days o f
c o n tin u o u s i r r a d i a t i o n a t th e grow ing temp­
e r a tu r e o f 68° F. The; ,c o le o p tile - 'le n g th
v a lu e s areii.an av erag e o f th e th r e e p r e ­
i r r a d i a t i o n g e rm in a tio n tr e a tm e n ts .
Average c o l e o p t i l e le n g th s o,f Karmont w in te r
w heat s e e d lin g s a t t h e . d i f f e r e n t wavelengths^
when exposed to one, tw o, and th r e e days, o f
c o n tin u o u s i r r a d i a t i o n a t th e grow ing temp-=
e r a t u r e o f 68° F. The c o l e o p t i l e le n g th
v a lu e s a re an a v erag e o f th e th r e e p r e ­
i r r a d i a t i o n g e rm in a tio n tr e a tm e n ts , ........................................
.i ■
32
33
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Page
F ig u re 7 .
A verage c o l e o p t i l e le n g th s o f Karmont w in te r
w heat s e e d lin g s a t th e d i f f e r e n t w av elen g th s
when grown, a t 45° F. and 68° F . The
c o l e o p t i l e le n g th v a lu e s a r e an av erag e o f th e
th r e e l i g h t exposure p e rio d s and th e th r e e
p r e - i r r a d i a t i o n g e rm in a tio n tr e a tm e n ts ,
35
8
ABSTRACT
Karmont w in te r w heat s e e d lin g s were g erm in ated f o r ' f o u r . and
f i v e .days a n d •exposed to a s p e c t r a l ra n g e from '4175 A ngstrom s' to 6400.
Angstroms f o r o n e, two and th r e e days fo ^ each g e rm in a tio n p e rio d a t
grow ing te m p e ra tu re s o f 68° F. and 45° F .
Exposure to th e ^spectrum
r e s u l t e d i n a r e t a r d a t i o n i n c o l e o p t i l e e lo n g a tio n f o r a l l w av elen g th s
s tu d ie d .
W avelength, p r e - i r r a d i a t i o n g e rm in a tio n tim e and exposure
tim e main e f f e c t s and t h e i r r e s u l t i n g i n t e r a c t i o n , w ith th e
e x c e p tio n o f . t h e p r e - i r r a d i a t i o n .g e rm in a tio n tim e x exp o su re tim e
i n t e r a c t i o n f o r th e 68P F. growing te m p e ra tu re , were s i g n i f i c a n t
a t th e one p e rc e n t l e v e l f o r b o th te m p e ra tu re s .
9
INTRODUCTION
Many f a c t o r s p la y im p o rta n t r o l e s i n t h e , developm ent o f any cro p
from th e i n i t i a t i o n o f g e rm in a tio n to th e m a tu ra tio n o f th e p l a n t .
In
soM p la n ts l i k e th e p e r e n n ia ls , t h i s p e rio d co v ers many y e a r s w h ile i n
o th e r case's developm ent i s lim it e d to one y e a r .
These f a c t o r s in c lu d e
d e p th o f s e e d in g , te m p e ra tu re , m o is tu re a v a i l a b i l i t y , n u t r i e n t s and
lig h t.
The change i n any one away from th e o p tim a l r e g io n , c au ses a d v e rse
e f f e c t s upon th e p l a n t , and may even r e s u l t i n d e a th .
When w in te r w heat i s s u b je c te d to u n fa v o ra b le e n v iro n m e n ta l co n d i­
t i o n s , and a s a r e s u l t th e growing p o in t o r c o le o p t ile (-*■) f a i l s to re a c h
th e s o i l s u rfa c e w ith in a re a s o n a b ly s h o r t tim e , an u n u su a l phenomenon
o ccu rs.
The p rim ary l e a f emerges from th e c o le o p t ile p r i o r to th e
emergence o f th e c o l e o p t i l e from th e gro u n d .
When t h i s o c c u rs th e
p rim ary le a v e s grow o u t and b a l l up due to t h e i r i n a b i l i t y to push
th ro u g h th e s o i l t o th e s u r f a c e .
S in ce th e p la n t i s t h e r e f o r e u n ab le
t o re a c h above th e s u rfa c e to o b ta in enough en erg y f o r l i f e , . i t d ie s .
T h is phenomenon seems to be d i r e c t l y a s s o c ia te d w ith u n fa v o ra b le
grow ing c o n d itio n s w hich do n o t a llo w th e c fo le o p tile to re a c h th e s o i l
s u rfa c e w ith in a r e l a t i v e l y s h o r t p e rio d o f tim e .
W ith th e s e f a c t s i n
mind i t was d e c id e d to d e term in e which f a c t o r o r f a c t o r s , l i s t e d above,
were r e s p o n s ib le f o r th e e a r l y b re a k th ro u g h o f th e p rim a ry le a v e s from
(l)
C o le o p tile i n t h i s p a p er r e f e r s t o what many a u th o rs c a l l th e
m esocotyl p lu s th e c o l e o p t i l e . I n o th e r w ords, th e e n t i r e shoot
from th e fa c e o f th e germ to th e t i p o f th e grow ing p o in t.
10
th e c o le o p t ile o
E a r lie r t e s t s have shown th a t w h ile th e r a t e o f
e lo n g a tio n was red u ced , tem perature and m o istu re s t r e s s a lo n e caused ,
no sh o rten in g in th e maximum o b ta in a b le le n g th o f th e c o l e o p t i l e ,
Even seed s p la n ted a t a s i x in ch depth a tta in e d th e same c o l e o p t i l e
le n g th as th o s e which were germ inated on b lo t t e r p ap er.
An in t e r e s t in g
i
d if f e r e n c e e x is t e d betw een seed s grown in l i g h t and seed grow n ,in
d a rk n ess.
The c o l e o p t i l e s o f th e se e d s grown in l i g h t stopped
e lo n g a tin g a s th e y reached th e s o i l S u rfa ce.
C o le o p t ile s d ev elo p in g
from se e d s grown in dark n ess elo n g a ted to h e ig h ts w e ll above th e s o i l
s u r fa c e .
A fte r having ,found th a t m o istu re s t r e s s , tem p era tu re, and depth
o f seed in g were n ot th e major f a c t o r s o f th e pre-em ergence phenomenon,
i t seemed p rob ab le th a t . l i g h t was a major f a c to r in c o l e o p t i l e
e lo n g a tio n in h ib it i o n and premature prim ary le a f em ergence.
11
REVIEW OF LITERATURE
The re s p o n se o f p la n ts to l i g h t has been phserv ed f o r y e a rs and
e x te n s iv e l i t e r a t u r e has been w r i t t e n oh th e s u b je c t.
F o r th e p u rp o ses
o f t h i s p a p e r, o n ly th o s e r e p o r t s d e a lin g c lo s e ly w ith th e c e r e a ls
w i l l be c o n s id e re d .
There a re s e v e r a l term s u s e d - in th e l i t e r a t u r e which r e q u ir e ex­
p la n a tio n s
One w a tt e q u a ls 621 lumens a t a w avelength o f 5560 A ngstrom s,
One Angstrom (A) e q u a ls IO- ^- m icro n s.
i s from 4000 A to 7500 A.
The ran g e o f th e v i s i b l e spectrum
The p o in t o f maximum v i s i b i l i t y i s a t 5560 A,
One e rg = IO- ^ w a tts x s e c , o r one e r g /s e c , = 10""^ w a tts .
I n h i b i t i o n p e rc e n ta g e e q u a ls
check ( d a rk c o n tr o l ) - t r e a t e d
check
A c tio n spectrum i s th e r e c ip r o c a l o f th e energy r e q u ir e d to induce
a-- g iv e n r e a c t i o n a t a g iv e n w av elen g th ,
W. W. G arner and H. A, A lla rd (8) “sh o u ld be c r e d ite d f o r th e
d is c l o s u r e and d e m o n stra tio n o f th e phenomenon o f p h o io p e rio d ism .
In
1906, th e y o b serv ed a s t r a i n o f M aryland N arro w leaf to b a cc o (N ic o tia n a
tabacum ) .which would n o t flo w e r and produce seed i n a norm al growing
p e r io d , no m a tte r what p h y s i o l o g i c a l 's t r e s s e s were a p p lie d .
The o n ly
means by which seed c o u ld be produced was to t r a n s p la n t th e p la n ts in
th e greenhouse d u rin g th e w in te r months d u rin g which tim e th e p la n ts
would flo w e r and produce se e d , .A fte r many ex p erim en ts w ith v a rio u s
p la n ts and l i g h t i n t e n s i t i e s , G arner and A lla r d in tro d u c e d two words
w hich w ould, alo n g w ith th e d e f i n i t i o n o f e a c h , e x p la in what th e y had
12
found; P h otop eriod ism to d e s ig n a te th e resp o n se o f an organism to the
r e l a t i v e le n g th o f day and n ig h t and p h o to p erio d to d e s ig n a te th e
fa v o r a b le le n g th o f day fo r each organism .
From t h e ir work th ey
concluded th a t " sex u a l rep ro d u ctio n can be a tta in e d by a p la n t o n ly
when i t i s exposed to a s p e c i f i c i a l l y fa v o r a b le le n g th o f d ay, and
exp osu re to a le n g th o f day u n fa v o ra b le to rep ro d u ctio n but fa v o ra b le
to growth ten d s to produce g ia n tism or i n d e f i n i t e c o n tin u a tio n o f
v e g e t a t iv e d ev elo p m en t, w h ile exp osure to a length' o f day fa v o ra b le
to sex u a l rep ro d u ctio n and to v e g e t a t iv e developm ent a l i k e , ex ten d s th e
p erio d o f sex u a l rep ro d u ctio n and ten d s to 6induce th e everbearing"
ty p e o f f r u it in g " .
I
C urrent r e se a r c h i s d is c lo s in g more and more s t a r t l i n g e f f e c t s
o f l i g h t upon p la n t s .
In h is work w ith tim oth y ( Phleum p r a te n s e ) . Gordon ( l l ) found
th a t l i g h t stim u la te d g erm in a tio n .
However, between 25 and 30 C. ■
-tim oth y
\
became r e l a t i v e l y l i g h t in s e n s it iv e ^
s p e c ie s which r e q u ir e l i g h t to g erm in a te.
th e r e ' are many o th er
Tobacco seed s show a
s i g n i f i c a n t in c r e a s e in g erm in ation p erce n ta g e when exposed fo r .
0 .0 1 secon d s to d ir e c t s u n lig h t ( 6 ) .
They a re so p h o t o s e n s it iv e th a t
stro n g m oon ligh t a p p lie d fo r 15 m inutes w i l l s tim u la te germ in ation ( 1 4 ) .
Borthwick and H endricks (3 ) found t h a t le t t u c e s e e d , which
germ in ates b e t t e r in th e p resen ce o f l i g h t , cou ld be stim u la te d by
'
■
exp osure to red l i g h t . F ar-red or in f a - r e d r a d ia t io n , how ever, would
i n h i b i t g erm in a tio n .
The amount o f en erg y n e c e ssa r y to i n h i b i t
13
g erm in ation i s 70 tim es g r e a te r than th a t req u ired to in d u ce g erm in a tio n .
Black and Wareing (2 ) found th a t th e in h ib it o r y e f f e c t s o f th e fa r -r e d
r a d ia tio n had an e f f e c t on B etu la p u b escen s,-up to 10 hours a f t e r exposure
The resp o n se o f o a t s , Avena s a t i v a . to l i g h t has been stu d ie d fo r
many y e a r s .
Some o f th e e a r l i e s t work w ith monochromatic l i g h t was
th a t done by Johnson (1 2 ) on th e f i r s t in tern o d e and c o l e o p t i l e o f
o a ts.
He fou n d , u sin g i n t e n s i t i e s o f 1 .2 e rg s/c m ^ /sec fo r each wave­
le n g th s tu d ie d , th a t th e m e s o c o ty l, th a t re g io n from th e s c u t e l l a r
node to th e c o l e o p t i l a r n od e, was in h ib it e d by exposure to monochromatic
lig h t.
The c o l e o p t i l e s , th a t re g io n from th e c o l e o p t i la r node to th e t i p
were stim u la te d by th e monochromatic l i g h t .
HoweveSr, due to th e
s h o r tn e ss o f th e m e s o c o ty l, which seems to have th e g r e a t e s t e f f e c t
on th e t o t a l le n g th a tta in e d by th e s e e d lin g ,o r s h o o t, th e t o t a l
s e e d lin g le n g th was s h o r te r under th e trea tm en t than under d a rk n ess.
When th e en ergy l e v e l was r a is e d to 13 ,e r g s /cm 2/sec th e in h ib it io n
o f th e f i r s t in te r n o d e was in c r e a se d co rresp o n d in g ly ' qver th a t o f th e
low er i n t e n s i t y .
Avery ( l ) d isc o v e r e d t h i s to be tr u e a l s o .
He found t h a t , a t
equal i n t e n s i t i e s , red l i g h t had th e g r e a t e s t e f f e c t on in h ib it in g th e
f i r s t in te r n o d e , green and b lu e were n ex t w ith v i o l e t b ein g th e l e a s t ,
e ffe c tiv e .
S ch n eid er (1 5 ) in h is work a t Harvard, showed th a t both the
c o l e o p t i l e and th e m eso co ty l o f o a ts were cap ab le o f a c t in g .a s ^their
.
own r e c e p to r
o f l i g h t stim u lu s .
..
He found th a t th e c o l e o p t i l e o f th e "-
14
young o a t p la n t was stim u la te d by red l i g h t a t i n t e n s i t i e s o f 0 ,5 to
8 ergs/m m ^ /sec.
C G leop tile ,„
A ll o f h is work was w ith a p ic a l segm ents o f th e
Went (1 8 ) found th a t th e extrem e 0 ,1 mm o f th e c o l e o p t i l e
t i p was th e most s e n s i t i v e to l i g h t .
From th a t p o in t downwardg th e
s e n s i t i v i t y dropped about 5000 tim es to a r a th e r c o n sta n t v a lu e fo r a l l
r e g io n s more than 2 mm d is t a n t from th e t i p .
Oat. p la n t s grown under co n tin u o u s exposure a t low. i n t e n s i t i e s ,
r e a c te d much th e same a s th e p la n t s r e c e iv in g high i n t e n s i t i e s fo r
sh o r t p e r io d s .
In t h i s work W eintraub (1 6 ) showed that- th e i n ­
h ib it i o n was dependent upon th e q u a lit y and q u a n tity o f l i g h t .
For
any g iv e n w a v elen g th , in h ib it io n was p r o p o r tio n a l to th e lo g a rith m
b ase 10 o f th e i n t e n s i t y and when he compared s e v e r a l i n t e n s i t i e s th e
a n g le s " o f s lo p e were eq u a l.
The in h ib it i o n e f f e c t s ,cover a w ide range
•
o f i n t e n s i t i e s fo r each w a v elen g th .
'
'
The low l i g h t i n t e n s i t i e s a f f e c t
c e l l d iv is i o n and th e h igh i n t e n s i t i e s r e ta r d e lo n g a tio n ,
Goodwin (9 )
in h is work fu r th e r confirm ed t h i s .
In l a t e r work, W eintraub (1 7 ) and h is a s s o c ia t e s found th a t red
l i g h t . (6234 A) i n i t i a l l y in h ib it e d a t 10~9 ergs/m m ^/sec w h ile t^lue in h ib it e d (4358 A) a t 10“° o5 ergs/mm2/ s e c . Complete in h ib it i o n was
■• •
.
>•
o b ta in ed a t IO"2 ergs/m m ^/sec fo r red l i g h t and 10 ergs/m m ^/sec fo r b lu e .
The p erce n t in h ib it i o n on f i n a l m eso co ty l le n g th was about p a r a lle l a t
d i f f e r e n t i n t e n s i t i e s o f th e same o rd er o f m agnitude.
th a t tem p eratu res had no e f f e c t on th e a c t io n c u r v e ..
I t was a ls o found
15
■The l i g h t range e f f e c t i v e fo r Avena in tern o d e in h ib it i o n was found by
Goodwin (1 0 ) to be from 6230 to 7100 A ngstrom s,
The a c t io n spectrum fo r
10% i n h i b i t i o n g ( t h o s e w a v elen g th s a t a g iv e n i n t e n s i t y w hich w i l l r e s u l t
in a red u c tio n in m eso co ty l le n g th o f 10% o f th e check^ was a t a minimum
a t about 5000 A, w ith a s l i g h t r i s e a t 4050 A , a sh o u ld er between 5700
and 5900 A, a r i s e betw een 6000 and 6200 A and a minimum e f f e c t i v e n e s s
a t 6230 A,
"The t o t a l amount o f in c id e n t energy req u ired to g iv e
th r e s h o ld in h ib it i o n s u sin g I to 15 second exp osu res and 100 hour exp osu res
i s w ith in th e same ord er o f m agnitude fo r th e w a v elen g th s stu d ie d " .
In ­
h ib it i o n o f th e m eso co ty l i s a complex phenomenon in v o lv in g a t l e a s t two
p r o c e s s e s , one much more l i g h t s e n s i t i v e than th e o th e r .
These are
p rob ab ly th e on es a f f e c t i n g c e l l d iv is io n , and c e l l O lo n g a tio n , r e s p e c t i v e ly .
Each p r o c e ss has a d if f e r e n t a c tio n spectrum ,.
.
Along w ith t h e ir work on le t t u c e seed g erm in a tio n ,-.Borthwick and
a s s o c ia t e s have done c o n s id e r a b le work on th e a c tio n spectrum fo r
b a r le y flo w e r in g (5 ) and fo r in h ib it io n o f th e second in te r n o d e (4 ) under
v a r io u s l i g h t regim es w ith e n e r g ie s v a r y in g ■10,000 f o ld and tim e o f
ir r a d ia t io n 100 f o ld ,
■In trea tm en ts w ith equal energy in which in t e n s it y ,
was v a r ie d from 0 ,2 5 to 25. fo o t ca n d le s.a n d 100 to one m inute e x p o su res,
an equal r e d u c tio n was o b ta in e d .
When e n e r g ie s v a r ie d , th e in h ib it io n
v a r ie d l i n e a r l y w ith th e lo garith m to b ase 10 o f the. en erg y ,
As th e
trea tm en ts moved from th e green re g io n o f th e spectrum o u t toward e it h e r
end, th e amount o f en ergy req u ired to o b ta in a g iv en resp o n se in c r e a se d .
The en ergy req u ired to i n h i b i t e lo n g a tio n i s 100 tim es th a t req u ired to
16
i n h i b i t flo w e r in g .
F l in t (7 ) w ith h is work on th e m eso co ty l o f co rn , found r e s u lt s
which were a lm o st o p p o s ite to th o se found by th e above a u th o r s.
He
found th e g r e a t e s t in h ib it i o n r e s u lt e d from exposure to b lu e l i g h t
w ith red g iv in g no resp o n se over w h ite l i g h t ,
s im ila r to th o se rep o rted in t h i s p ap er.
His r e s u l t s a re q u ite
17
MATERIALS AND METHODS
A ll t e s t s were conducted u sin g Karmont w in ter wheat which i s a
b eard ed , w h ite c h a f f e d , w in te r hardy v a r i e t y .
To e s t a b lis h a sou rce o f l i g h t which would be rea so n a b ly
m onochrom atic, a box was c o n str u c te d w ith th e fo llo w in g demensions*
The l i g h t sou rce c o n s is t e d o f a 200 w a tt c le a r W estinghouse bulb
mounted so th a t i t s fila m e n t a cted a s a l i n e sou rce r e p la c in g th e
u su al en tran ce s l i t in th e ord in a ry sp ectro g ra p h .
The b ulb was
s h ie ld e d and th e l i g h t d ir e c t e d , by means o f a l e n s , through one 60°
and two 30° p r ism s, o f number 2 dense f l i n t g l a s s , which bent th e
l i g h t 90° and d is p e r s e d i t .
The spectrum covered an e ig h t by ten
in c h area a t a fo c u s s in g d is ta n c e o f e ig h t f e e t ( F ig u re I ) .
A ccess to
th e s p e c tr a l re g io n was gain ed through an opening a t th e b lu e end o f
th e spectrum .
W avelengths were determ ined v i s u a l l y by a g r a tin g
7000-
6500 -
6000 ^
5750550052505000 -
4750450042504000 —
P o s it io n o f 15/16" germ ination boxes under th e spectrum
F ig u re I .
The lo c a t io n o f th e s p e c tr a l re g io n s f o r each box in th e sp ecto g rap h
a t a f o c a l d is ta n c e o f e ig h t f e e t .
s p e c tr o s c o p e .
The spectrum covered a d is t a n c e - o f from 4100 to
6500 Angstroms (A ).
An i n t e n s i t y o f th r e e fo o t-c a n d le s- was. measured a t
5560 A th e r e g io n o f maximum v i s i b i l i t y , w ith a General E le c t r ic
p h o t o e le c t r ic l i g h t m eter.
The e n t ir e ap p aratus was p la c e d in a
dou ble door darkroom so th a t no l i g h t o th e r than th e spectrum was
a v a ila b le to th e s e e d s .
Copper c o i l s , 3 /8 ," were p la c e d around the
o u t s id e a t s ix in ch in t e r v a l s to a h e ig h t o f 3 .5 f e e t .
Cold w ater
was run through th e c o i l s to- m ain tain th e growing r e g io n a t a co n sta n t
tem p eratu re.
The minimum tem perature which was a t t a in a b le from such a
system was 60° F.
Four seed s were p la ce d in each o f two 1 5 /l6 "
p l a s t i c germ in a tio n d is h e s and p la ce d in th e h o ld in g b ox.
Ten double
rows o f boxes covered th e s p e c tr a l r e g io n , two b o x e s-p e r r e g io n .
The
bottom s o f th e g erm in a tio n boxes were removed and rep la c e d w ith b lo t t e r
paper so th a t enough m o istu re was a v a ila b le to th e p la n t throughout th e
e n t i r e growing p e r io d .
A ll seed was t r e a t e d w ith 10% P h y g o n -flo u r
m ixtu re b e fo r e t e s t i n g .
The 1 5 /1 6 in ch p l a s t i c g erm in ation boxes were
p la ce d in s id e wooden boxes 1 1 .5 x 2 .5 x 5 .5 inches-, on top o f a one in ch
la y e r o f s t e r i l i z e d Z o n o lite in s u la t in g m a te r ia l.
A ll o f th e wooden
boxes were p a in te d with- a b lack w ater r e s i s t a n t p a in t .
-. To m ain tain com p lete d a rk n ess, th e wooden boxes were f i t t e d w ith
s lid i n g l i g h t - t i g h t l i d s .
T h is w.as n e c e s s a r y s in c e th e m a te r ia l had to
be tr a n sp o r te d from th e growth chamber to th e l i g h t so u rce fo r treatm en t
and back to th e growth chamber a f t e r trea tm en t.
■Two te m p e r a tu r e -lig h t t r i a l s were con d u cted , one a t a germ inator
20
tem perature o f 68° F 9 l i g h t sou rce tem perature o f 70° F and an oth er
w ith th e germ inatqr tem perature o f 45o F 9 l i g h t sou rce tem perature
600 Fo
The t e s t s covered th r e e l i g h t p e r io d s and th r e e germ in ation
p e r io d s .
The g erm in a tio n p e r io d s were m aintained c o n sta n t and the
l i g h t p erio d was v a r ie d fo r each t e s t .
The t e s t ran a s fo llo w s?
Three days g erm in a tio n p lu s o n e, tw o, and th r e e -d a y s under l i g h t ,
fo llo w e d by s i x , f i v e and fo u r days in th e germ inator to make a t o t a l
t e s t p erio d o f ten d a y s.
Ten days was th e amount o f tim e req u ired fo r
th e prim ary le a v e s to emerge from th e c o l e o p t i l e a t th e warm tem perature
(7 0 ° F0) o
The c o ld (4 5 ° F . ) t e s t was conducted in th e same manner as
th e warm, trea tm en t e x c e p t th a t th e g erm in a tio n p e r io d .f o llo w in g lig h t..w a s
2 3 ,2 2 , and 21 days r e s p e c t i v e ly .
At th e end o f th e h o ld in g p erio d
th e r e was s t i l l no a p p r e c ia b le growth so a l l boxes were p la c e d a t a
70° F tem perature fo r seven a d d itio n a l d a y s.
■ To d eterm in e from what d ep th s th e c o l e o p t i l e s would emerge under
c o n d itio n s o f normal day l i g h t and com p lete d a rk n ess, a depth o f
p la n tin g t r i a l was c o n d u c te d .. Ten seed s were placed, a t d ep th s ranging
from one to s ix in c h e s in c y lin d r ic a l i c e cream c o n t a in e r s .
On h a lf
o f th e .c o n t a in e r s were covered to p rev en t l i g h t p a ssa g e and th e
o th e r -h a lf were covered w ith c le a r C ello p h a n e.
These c o n ta in e r s were
p la c e d in th e greenh ou se in a randomized com p lete b lo ck d e s ig n o f th ree
r e p lic a tio n s .
D ate o f emergence and f i n a l c o l e o p t i l e le n g th were reco rd ed .
S ig n if i c a n t mean d if f e r e n c e s fo r main e f f e c t s and in t e r a c t io n s were
o b ta in ed by S c h e fffe 5S mqthod o f m u ltip le com parison
(1 4 )•
21
RESULTS
G reenhouse ddpth. o f p la n tin g e x p e rim e n t.
The c o l e o p t i l e s o f s e e d lin g s w hich w ere grown i n c o n ta in e rs , which
ex clu d ed a l l l i g h t , e lo n g a te d - above th e s o i l s u rfa c e a t o n e , two and
th r e e in c h p la n tin g s (F ig u re 2 ) 0 ■The c o le o p t i l e s o f th e s e e d lin g s
w hich were grown i n th e c l e a r p l a s t i c co v ered c o n ta in e r s , e lo n g a te d
o n ly to th e s o i l s u r f a c e » At th e f o u r in c h d e p th o f p la n tin g th e
c o l e o p t i l e s i n b o th th e d a rk and l i g h t c o n d itio n s d id n o t e lo n g a te to
th e s o i l s u r f a c e .
The av erag e c o l e o p t i l e le n g th s - o f th e s e e d lin g s
grown i n th e l i g h t e x c lu d in g c o n ta in e r s exceeded th e a v erag e le n g th
o f th e c o l e o p t i l e i n th e l i g h t exposed c o n ta in e r s .
C o le o p tile e lo n g a tio n re s p o n s e s to' p r e - i r r a d i a t i o n g e rm in a tio n and
l i g h t exposure a t A5° F . growing te m p e ra tu re s .
■
"
‘
;
• E xam ination o f th e a n a ly s is o f v a ria n c e d a ta , T ab le I , shows
s t a t i s t i c a l d if f e r e n c e s f o r a l l tre a tm e n ts and tre a tm e n t combina­
tio n s .
U sing S c h e ffe 1s method o f m u ltip le com parisons (14)
. s t a t i s t i c a l l y s i g n i f i c a n t d if f e r e n c e s were c a lc u la te d f o r a l l main
.
'
.
.
e f f e c t s and f i r s t o rd e r in te r a c tio n s ( T a b le I I ) . A com parison o f th e
d a ta f o r main e f f e c t s (T able I I I ) u s in g th e c a lc u la te d d if f e r e n c e s
from T able I I , shows t h a t s i g n i f i c a n t d if f e r e n c e s a t th e I p e rc e n t
l e v e l e x i s t betw een th e d a rk tre a tm e n t, and a l l l i g h t tre a tm e n ts
f o r th e w avelength means.
The p r e - i r r a d i a t i o n g e rm in a tio n means
d i f f e r s i g n i f i c a n t l y when th e fo u r day g e rm in a tio n i s compared w ith
b o th th e th r d e and f iv e day g e rm in a tio n .
When th e ex p o su re tim e
22
Dark
Depth o f p la n tin g ( in c h e s )
F igu re 2 .
C o le o p t ile le n g t h s ,a t v a r io u s p la n tin g d ep th s under
c o n d itio n s o f normal d a y lig h t and d a rk n ess, o f s e e d lin g s
grown in th e g reen h o u se.
23
T ab le I .
A n a ly sis o f v a ria n c e f o r th e re sp o n se o f Karmont w in te r
w heat c o l e o p t i l e s to w a v ele n g th , p r e - i r r a d i a t i o n g e rm in a tio n
tim e and exposure a t a g e rm in a tin g te m p e ra tu re o f 45° F,
Source o f v a r i a t i o n
D egrees o f freedom
Mean square
W avelength
9
6 ,5 7 1 .5 4 * *
P r e - i r r a d i a t i o n g e rm in a tio n tim e
2
1 9 ,1 8 2 .6 0 * *
Exposure tim e
2
4 ,2 3 7 .0 7 * *
W avelength x p r e - i r r a d i a t i o n
18
3 ,1 9 0 .5 0 * *
W avelength x exposure tim e
18
1 ,5 6 0 .9 1 * *
4
3 ,2 3 0 .7 9 * *
W avelength x p r e - i r r a d i a t i o n x exposure
E rro r
630
T o ta l
719
** s i g n i f i c a n t a t th e I p e rc e n t l e v e l
712.79
24
T able I I .
D iffe re n c e s betw een means o f main e f f e c t s and i n t e r a c t i o n s
n e c e s s a ry f o r s ig n if ic a n c e u s in g S c h e ffe 1s method o f m u ltip le
com parisons
E ffe c t
Mean d if f e r e n c e n e c e s s a ry f o r s ig n if ic a n c e (mm)
or
45Q F.
__________6 8 2_L __________
i n t e r a c t i o n ________ 1$ l e v e l
5% l e v e l
1% l e v e l
5% l e v e l
2 0 .8 7
1 8 .3 8
17.19
15.15
P re -irra d ia tio n
g e rm in a tio n tim e
7 .3 9
5 .9 3
6 .0 7
4 .9 2
Exposure tim e
7 .3 9
5.9 3
6 .0 7
4 .9 2
W avelength x
P r e - i r r a d i a t i o n tim e
54.20
50.40
4 4 .7 7
4 1 .6 0
W avelength x
Exposure tim e
54.20
50.40
4 4 .7 7
4 1 .6 0
P r e - i r r a d i a t i o n tim e
x exposure tim e
1 9 .2 4
1 6 .7 1
1 5 .8 7
1 3 .8 0
W avelength
T ab le I I I .
Average c o le o p t ile le n g th s o f Karmont w in te r wheat f o r th e main e f f e c t s , w av elen g th s,
p r e - i r r a d i a t i o n g e rm in a tio n tim e and exposure tim e and th e w avelength x p r e - i r r a d i a ­
t i o n g e rm in a tio n and w avelength x exposure tim e in te r a c t i o n s a t th e 45° F. and
68° F. growing te m p e ra tu re s .
_______ __________
_________ A verage c o le o p t ile le n g th s i n m illim e te rs __________ ________________ _
Wave45° F 0 growing te m p e ra tu re
68 F. growing te m p e ra tu re
le n g th
G erm ination
_______Exposure______ _
G erm ination__________ Exposure ______
(A) 3 days 4 days 5days I day. 2 day s 3 days Mean 3 days 4 days 5 days I day 2 days 3 days Mean
4175
4310
4460
4625
4800
5040
5375
5840
6400
Dark
Mean
5 7 .4
6 0 .2
6 5 .4
56.5
56.7
6 4 .0
5 5 .8
53.2
5 5 .4
7 5 .2
6 0 .0
1 8 .2
2 8 .2
2 4 .2
4 2 .1
34.2
56.2
51.2
4 7 .4
6 1 .9
7 0 .1
4 3 .4
6 4 .2
4 6 .8
54.8
6 2 .1
4 6 .1
4 3 .6
4 6 .1
34.5
3 7 .0
8 1 .7
51.6
4 4 .7
58.6
5 0.0
5 5 .7
4 2 ,2
53.9
54.0
4 4 .6
4 8 .2
7 2 .4
52 .4
6 1 .0
4 2 .2
51.5
4 8 .4
3 9 .4
6 2 .0
51 .0
5 9 .4
4 7 .8
7 5 .0
53 .8
3 4 .0
3 4 .4
4 4 .0
5 6 .7
5 5 .4
4 7 .0
4 7 .7
3 1 .0
58.2
79 .5
4 8 .8
4 6 .6
4 5 .1
4 8 .2
53 .6
4 5 .7
54.3
51 .0
4 5 .1
5 1 .4
7 5 .7
3 .6
1 6 .7
8 .4
4 8 .5
1 2 .1
1 7 .0
1 8 .5
1 3 .6
1 4 .0
5 0.8
2 6 .1
1 9 .7
1 3 .7
1 5 .0
21 .3
1 6 .0
1 4 .6
3 9 .1
4 2 .5
4 3 .4
6 8 .7
3 6 .4
10 .5
3 .0
4 .0
4 .9
3 .3
1 8 .5
21 .2
1 0 .4
3 2 .9
58.2
2 5 .7
21.2
16 .6
1 1.3
26 .6
1 3 .0
16.6
24 .2
16.3
36 .8
69.5
33.2
1 0 .5
2 .0
6 ,8
2 6 .6
1 4 .0
2 7 .8
2 9 .0
2 5 .6
3 9 .4
5 7 .4
3 1 .9
2 .2
1 4 .6
9 .2
1 9 .2
4 .4
5 .6
2 5 .8
2 4 .6
1 4.2
50.7
2 3 .0
11.2
11.2
9 .3
24.1
1 0 .4
1 6 .7
26 .3
24.5
30.1
59.2
26
means are compared th e r e i s no s i g n i f i c a n t d if f e r e n c e a t th e f i v e
p e r c e n t l e v e l u sin g th e S - method o f com parison.
The s ig n if ic a n c e e x h ib ite d by th e w avelen gth x l i g h t exposure
tim e in t e r a c t io n (T ab le I ) can be seen from th e grap h ic p r e s e n ta tio n
o f t h i s in t e r a c t io n in F ig u re 3 .
The d iv e r g e n t resp o n se s e x h ib ite d
by th e c o l e o p t i l e s a t 4175 A 8 4310 A and a g a in a t 5840 A would
accou n t fo r t h i s s i g n i f i c a n c e .
The g r e a t e s t s t a t i s t i c a l d if f e r e n c e i s
between 4175. A9 4310 A and 5840 A and th e dark treatm en t a t th e th ree day
!exposure.
T h is same d iv er g en ce i s seen a g a in in F igu re 4 , where the
w avelen gth x p e r - ir r a d ia t io n germ in ation tim e in t e r a c t io n i s p re se n te d .
The w ide se p a r a tio n betw een p o in t s in th e 4175 A to 4800 A reg io n and
a gain in .th e 5840 A to 6400 A reg io n i s a g a in , s t a t i s t i c a l l y ^ ' s i g n i f i c a n t .
F u rth er s ig n if ic a n c e i s shown by th e o p p o s ite s lo p e s - o f :t h e !fo u r and
f i v e day p r e - ir r a d ia t io n l i n e s .
The exp osure tim e x p r e - ir r a d ia t io n germ in ation tim e in t e r a c t io n
i s p resen ted in T able IV.
T able II shows a d if f e r e n c e ,a t th e I p ercen t
l e v e l g o f . 1 9 .2 4 , n e c e s s a r y f o r /.s ig n if ic a n c e y . -=This s i g n i f i c a n t d if f e r e n c e
is-fou n d -.b etw een th e ;th ree d a y e x p o su re, fou r day g erm in ation mean and
th e one and two day ex p o su re, th r e e day g erm in ation means and th e th ree
day ex p o su re, f i v e day g erm in ation mean.
A s i g n i f i c a n t d if f e r e n c e
e x i s t s between th e two day ex p o su re, fo u r day germ in ation mean and th e
two day ex p o su re, fou r day germ in ation mean.
27
WW
78
X - I day l i g h t exposure
0 -2
72
/
I
day l i g h t exposure
I?
I i*
A - 3 day l i g h t exposure
66
I
I
60
I
!
Il
Il
a
64
j
S’ 30
24
78
/2
6
46*
£040
tf3 #
------
S S 44 _
W avelength (Angstroms)
j gure 3. Average c o l e o p t i l e le n g th s o f Karmont w in te r w heat s e e d lin g s
a t th e d i f f e r e n t w av elen g th s when grown exposed t o , o n e, tw o, and th r e e
days o f c o n tin u o u s i r r a d i a t i o n a t th e grow ing te m p e ra tu re o f £5° F„ The
c o l e o p t i l e le n g th v a lu e s a re an av erag e o f th e th r e e p r e - i r r a d i a t i o n
g e rm in a tio n tr e a tm e n ts .
28
WW
80
X - 3 days o f p r e - i r r a d i a t i o n g e rm in a tio n
12
0 - 4 days o f p r e - i r r a d i a t i o n g e rm in a tio n
A - 5 days o f p r e - i r r a d i a t i o n g e rm in a tio n
66
A,
60
/
/
\
~X--------------
-54
/
\ /
/
y
CD
i— I
I
I
/
/
/
Jl
/
.,A
a ^
/\
\
?
-A
/
0
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1
NX
6
/8
/ 2-
6 ■
6400
^ ^ 3 ,A
0
V
2co ^
5575
^
DAkK
W avelength (Angstroms)
F ig u re 4« Average c o l e o p t i l e le n g th s o f Karmont w in te r w heat s e e d lin g s
a t th e d i f f e r e n t w av elen g th s when g erm in ated f o r t h r e e , f o u r and f iv e
days p r i o r to i r r a d i a t i o n a t th e grow ing te m p e ra tu re o f 45° F„ The
c o l e o p t i l e le n g th v a lu e s a re an a v erag e o f th e th r e e l i g h t l e v e l s .
29
T able TV.
Average c o l e o p t i l e le n g th s o f Karmont w in te r w heat f o r th e
p r e - i r r a d i a t i o n g e rm in a tio n tim e x exposure tim e i n t e r a c t i o n
a t th e 45° F . and 68° F. grow ing te m p e ra tu re s .
Average c o l e o p t i l e le n g th in m illim e te r s
45° F. growing te n ro e ra tu re
G erm ination
Exposure
I
2
3
G erm ination
Mean
exp o su re
68° F
grow ing te m p e ra tu re
G erm ination
sxposure
3 days
4 days
5 days
Mean
3 days
6 0 .3
6 6 .5
53.2
5 1 .6
4 1 .8
3 6 .8
4 5 .2
53.1
56.4
5 2.4
53 .8
4 8 .9
27.5
2 9.0
2 1 .8
4 1 .8
3 9 .8
2 7 .5
3 0 .4
27 .0
1 9 .8
6 0 .0
4 3 .4
5 1 .6
2 6 .9
3 6 .4
25 .7
4 days 5 days
Mean
3 3 .2
3 2 .0
2 3 .0
30
C o le o p tile e lo n g a tio n re s p o n se s to p r e - i r r a d i a t i o n g e rm in a tio n and
l i g h t exposure a t 68° F0 growing te m p e ra tu re s .
The a n a ly s is o f v a ria n c e t a b l e , T ab le V., p o in ts o u t t h a t a l l
main e f f e c t s and th e f i r s t o rd e r in te r a c t io n s :, w ith th e e x ce p tio n of
th e p r e - i r r a d i a t i o n g e rm in a tio n tim e x ex p o su re tim e i n t e r a c t i o n a re
s ig n ific a n t
a t th e one p e rc e n t l e v e l .
The d if f e r e n c e s betw een means f o r th e main e f f e c t s and
i n t e r a c t i o n s n e c e s s a ry f o r s t a t i s t i c a l s ig n if ic a n c e u s in g th e S method a re p re s e n te d i n T able I I .
U sing th e s e d if f e r e n c e s in
T ab le I I I th e s e main e f f e c t s d if f e r e n c e s a re o b serv ed .
The
d if f e r e n c e betw een th e d a rk tre a tm e n t and a l l l i g h t tr e a tm e n ts
i s s i g n i f i c a n t a s i s th e d if f e r e n c e betw een th e re d (6400 A)
w avelength tre a tm e n t and 4175 A, 4310 A, 4460 A and 4800 A
tr e a tm e n ts .
A f iv e p e rc e n t s i g n i f i c a n t d if f e r e n c e e x i s t s betw een
th e 5375 A tre a tm e n t and th e 4310 A, 4460 A and 4800 A tr e a tm e n t.
F ig u re 5
i l l u s t r a t e s th e s t a s t i s t i c a l s ig n if ic a n c e s o f
th e w avelength x exposure tim e i n t e r a c t i o n .
A s ta tis tic a l
s i g n i f i c a n t d if f e r e n c e i s observed a t 4175 A between th e one and
th r e e day e x p o su re , a t 4310 A betw een one and two and th e two and
th r e e day exp o su res and a t 4625 A betw een th e two and th r e e day
e x p o su res a t 5040 A.
The one and th r e e and two and th r e e day
ex p o su res a t 6400 A a re a ls o s i g n i f i c a n t l y d i f f e r e n t .
The w avelength x p r e - i r r a d i a t i o n g e rm in a tio n tim e i s p re s e n te d
i n F ig u re 6 .
S t a t i s t i c a l s ig n if ic a n c e i s i l l u s t r a t e d a t 4175 A
31
T able V.
A n a ly sis o f v a ria n c e f o r th e re s p o n se o f Karmont w in te r
wheat c o l e o p t i l e s to w a v ele n g th , p r e - i r r a d i a t i o n tim e and
exposure tim e a t a growing te m p e ra tu re o f 68° F„
Source o f v a r i a t i o n
D egrees o f freedom
Mean square
W avelength
9
1 6 ,8 6 8 .3 5 * *
P r e - i r r a d i a t i o n g e rm in a tio n tim e
2
8 ,8 7 8 .2 7 * *
Exposure tim e
2
7,4 1 9 .2 6 * *
W avelength x p r e - i r r a d i a t i o n
18
972.30**
W avelength x exposure tim e
18
1 ,1 2 2 .5 7 * *
4
449.96
36
1 ,3 8 4 .5 0 * *
E rro r
630
4 8 6 .1 9
T o ta l
719
P r e - i r r a d i a t i o n x exposure tim e
W avelength x p r e - i r r a d . exposure tim e
** S ig n i f ic a n t a t th e I p e rc e n t l e v e l
32
-mm
X - I day l i g h t e x p o su re.
0 -2
72
day l i g h t e x p o su re .
A - 3 day l i g h t e x p o su re.
<56
6o
si
I
<D
f—
I
<D
f—I
48
I
•H
A
O
Q)
i—I
O
0
0)
1
A
/,
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Il
Il
/8
/2
6
/
XX
V 'V
F
," " O '
/
ay /
z
/f
/
//
z 7
/
/
/
/
N
A/
4175 4460
4300
45/0
4625
5040
^375
5340
OastJ(
W avelength (Angstroms)
F ig u re 5. Average c o l e o p t i l e le n g th s o f Karmont w in te r w heat s e e d lin g s
a t th e d i f f e r e n t w av elen g th s when exposed to one, two and th r e e days
o f c o n tin u o u s i r r a d i a t i o n a t th e grow ing te m p e ra tu re o f 6c.0 F. The
c o l e o p t i l e le n g th v a lu e s a re an a v erag e o f th e th r e e p r e - i r r a d i a t i o n
g e rm in a tio n tr e a tm e n ts .
33
inm-i
78'
X - 3 days p r e - i r r a d i a t i o n g e rm in a tio n
72
0 -4
days p r e - i r r a d i a t i o n g e rm in a tio n
A - 5 days p r e - i r r a d i a t i o n g e rm in a tio n
6^4
■&4B
0)
I—
! y
/
I,
I
I
^
/
I
I
I
I I
I
^ 36rj
O
0
\
I
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I
I
I
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1
I
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I
/
A
!/
/264
I
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/V
VIrz A
I
i ------------k /
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--A r'
4lrS43/04/f60462S4gO° ^040
SZTS
584-0
W avelength (A ngstrom s)
F ig u re 6 . Average c o l e o p t i l e le n g t h s o f Karmont w in te r wheat s e e d lin g s
a t th e d i f f e r e n t w a v elen g th s when exposed t o on e, two and th r e e days o f
co n tin u o u s ir r a d ia t io n a t th e growing tem perature o f 6 8° F , The
c o l e o p t i l e le n g th v a lu e s a re an average th e th r e e p r e - ir r a d ia t io n
germ in ation trea tm en ts.
^
v
f v
'
>
* "
34
betw een th e th r e e and f i v e and th e fo u r and f iv e day g e rm in a tio n
tim e .
S ig n ific a n c e i s a ls o shown a t 5375 A betw een th e th r e e and ...four
and th e fo u r and .f iv e day g e rm in a tio n tim e .
i s seen a t 5840 A.
T h is same d if f e r e n c e
The th r e e and f iv e and th r e e and f o u r day
g e rm in a tio n tim e a t 6400 A a re a ls o s i g n i f i c a n t .
Average e f f e c t o f w av elen g th s upon c o l e o p t i l e e lo n g a tio n a t th e 45° F.
and 68° F. grow ing te m p e ra tu re s .
A. com parison betw een th e w av elen g th means a t th e grow ing
te m p e ra tu re s o f 45° F . and 68° F . i s p re s e n te d i n F ig u re 7 ,
The
two te m p e ra tu re s te n d ed to e x h ib it p a r a l l e l e f f e c t a t a l l w avelengths
w ith m ajor d if f e r e n c e s e x is t in g a t 4460 A, where th e 45° F . t e s t shows
an in c r e a s e i n re s p o n se w h ile th e 68° F. t e s t shows a d e c re a s e in
re s p o n s e .
A nother d if f e r e n c e e x i s t s a t 5375 A where th e 45° F. t e s t
d e c re a s e s in e f f e c t over th e p ro c e ed in g w av elen g th and th e 68° F. t e s t
in c r e a s e s i n e f f e c t over th e p ro c e e d in g w av elen g th .
th e check th e e f f e c t s ap p ear p a r a l l e l i n n a tu r e .
From 5375 A th ro u g h
35
WltH
78
O - 45° F. growing te m p e ra tu re
72
A - 68° F. growing te m p e ra tu re
66 60
si
S4
I
M
Q)
st /
'I 4 2
O
0)
r -l
S 36
a)
sP
^
30
<6
--------------------
IS
I
/2
A
I
,
4 rrsM 4* 0*
/
/
\
/
^ 00 SVO
S* w
SVO
ZM^c
W avelength (Angstroms)
F ig u re 7. Average c o l e o p t i l e le n g th s o f Karmont w in te r w heat s e e d lin g s
a t th e d i f f e r e n t w av elen g th s when grown a t 45° F. and 68° F. The
c o l e o p t i l e le n g th v a lu e s a re an av erag e o f th e th r e e l i g h t exposure
p e rio d s and th e th r e e p r e - i r r a d i a t i o n g e rm in a tio n tr e a tm e n ts .
36
DISCUSSION
P re lim in a ry o b s e rv a tio n s .
I n p re lim in a ry t e s t s to d eterm in e th e ran g e o f ’i n h i b i t i o n which
was p o s s ib le w ith th e a p p a ra tu s d e s c rib e d i n m a te r ia ls and m ethods,
some i n t e r e s t i n g re s p o n se s were o b se rv e d «
When exposed f o r p e rio d s g r e a te r th a n f i v e d a y s , th e seed s under
th e spectrum d id n o t dev elo p a s th e ex p o su re tim e advanced.
When
see d was exposed f o r n in e d a y s, o n ly th e seed which was exposed to th e
r e d re g io n o f th e spectrum (6400 A) re c o v e re d from t h e .tr e a tm e n t»
When seed was exposed f o r e ig h t d a y s, v e r n a liz e d , and p la n te d in
th e greenhouse f o r f u r t h e r o b s e r v a tio n , th e p la n ts w hich developed
from th e red. exposed seed r e q u ir e d seven more days to head th a n d id
th e p la n ts from th e seed which had been exposed to th e b lu e (4175A)
re g io n o f th e sp ectru m .
The seed from th e re d exposed p l a n t s was s h r iv e le d ,
w h ile th e seed from th e b lu e exposed p l a n t s ap p eared n o rm al.
G reenhouse d e p th o f p la n tin g e x p e rim e n t.
The a b i l i t y o f th e c o l e o p t i l e s o f Karmont w in te r w heat to emerge
from th e s o i l s u rfa c e from d e p th s up t o th r e e in c h e s u n d er c o n d itio n s o f
a b s o lu te d a rk n e ss and norm al d a y lig h t, i s seen i n f ig u r e 2 .
The a p p a re n t i n h i b i t i n g e f f e c t t h a t l i g h t has upon th e c o le o p t ile
le n g th s i s shown by th e grow th o f th e c o le o p t i l e s above th e s o i l s u rfa c e
when grown i n th e absence o f l i g h t .
The c o le o p t ile s from s e e d lin g s
grown under c o n d itio n s o f norm al d a y lig h t sto p p ed e lo n g a tin g upon
37
re a c h in g th e s o i l s u r f a c e ,
At th e fo u r in c h p la n tin g d e p th , which./was
g r e a t e r in .d e p th th a n th e .average maximum o b ta in a b le le n g th o f th e
r
c o l e o p t i l e s , th e c o l e o p t i l e s o f th e d a rk grown s e e d lin g s e lo n g a te d to
g r e a t e r le n g th s th a n th e c o l e o p t i l e s o f th e s e e d lin g s grown under
norm al d a y l i g h t „
T h is would in d ic a te a p o s s ib le i n h i b i t i n g e f f e c t
o f l i g h t p e n e tr a tin g th e s o i l s u r f a c e .
The r e d u c tio n in c o le o p t ile
le n g th a t th e f o u r , f i v e and s i x in c h d e p th s would in d ic a te an
a p p a re n t d e p re s s in g e f f e c t o f s o i l d e p th upon th e c o l e o p t i l e .
T h is ex p erim en t a ls o in d ic a te d t h a t th e r e i s some o th e r f a c to r
w hich s to p s th e e lo n g a tio n o f th e c o l e o p t i l e .
-
At th e o n e, tw o, and
th r e e in c h d a rk p l a n t i n g , th e c o l e o p t i l e s e lo n g a te d t o a p p ro x im a te ly
one in c h above th e s o i l s u rfa c e and s to p p e d .
These c o l e o p t i l e s were
f a r s h o r t o f t h e i r maximum p o t e n t i a l w hich i s a p p ro x im a te ly 80 mm,
when th e s e e d lin g s a re grown in d a rk n e ss on b l o t t e r p a p e r.
I t i s th e re ­
f o r e a p p a re n t t h a t some f a c t o r , o th e r th a n l i g h t , te m p e ra tu re , and d ep th
o f seed in g
has an e f f e c t upon th e le n g th a t t a i n a b l e by th e c o le o p t ile s
when grown i n s o i l ' i n th e absence o f l i g h t .
C o le o p tile e lo n g a tio n re s p o n s e s to o r e - i r r a d i a t i o n g e rm in a tio n and
l i g h t exposure a t A 5°.F. growing te m p e ra tu re s .
■
The g e n e ra l re s p o n se o f th e c o l e o p t i l e s to w av elen g th s a t th e
c o ld e r (45° F . ) grow ing te m p e ra tu re , was l e s s th a n th e re s p o n se a t th e
warm (68° F .) grow ing te m p e ra tu re (F ig u re 7 ) . . T his d if f e r e n c e i s
a p p a r e n tly due to th e e a r l i e r s ta g e o f developm ent t h a t th e s e e d lin g s
Were a t , a t th e tim e o f e x p o su re , due to th e slow er r a t e o f developm ent
v
38
b ro u g h t about by th e c o ld te m p e ra tu re ,
At t h i s c o ld e r te m p e ra tu re , th e e f f e c t o f th e w a v ele n g th s i s
f o r an o v e r a ll d e p re s s io n in th e c o l e o p t i l e le n g th , and no s t a t i s t i c a l l y
s i g n i f i c a n t d if f e r e n c e s e x i s t ' betw een any o f th e w av elen g th means.
The
g e rm in a tio n tim e p r i o r to exposure seems to be a d e f i n i t e f a c t o r in
th e re sp o n se o f th e c o l e o p t i l e s to i r r a d i a t i o n ,
.The s h o r t e s t (th re e
day) p r e - i r r a d i a t i o n g e rm in a tio n tim e , r e s u l t e d in th e l e a s t c o le o p t ile
i n h i b i t i o n , w h ile th e f o u r days o f g e rm in a tio n p r i o r to exposure r e s u l t e d
i n th e g r e a t e s t c o l e o p t i l e i n h i b i t i o n .
The s ig n if ic a n c e o f th e w av elen g th x exp o su re tim e i n t e r a c t i o n
(F ig u re 3) is. th e r e s u l t o f th e in c o n s i s te n t re s p o n se s o f th e
c o l e o p t i l e s to th e w av elen g th .
When th e amount o f p r e - i r r a d i a t i o n tim e was p l o t t e d a g a in s t th e
w a v ele n g th , a n e g a tiv e l i n e a r r e l a t i o n s h i p betw een c o l e o p t i l e le n g th
- /'
and w avelength w a s.in d ic a te d f o r th e fo u r day g e rm in a tio n p e rio d . T his
was o p p o s ite to th e re s p o n se Of th e th r e e and f iv e d a y ' g e rm in a tio n
p e r io d s .
The v a l i d i t y o f th e s e re s p o n se s i s q u e s tio n e d a n d ' f u r th e r
t e s t s w i l l .be n e c e s s a ry . . ■ '
C o le o p tile e lo n g a tio n re s p o n s e s to o r e - i r r a d i a t i o n g e rm in a tio n , a n d '
■li g h t exposure a t 68° F, growing te m p e ra tu re s .
The g e n e ra l, i n h i b i t o r y e f f e c t o f a l l w av elen g th s used i n t h i s
i n v e s t i g a t i o n was g r e a t e r a t th e 68° F . grow ing te m p e ra tu re th a n a t th e
45° F. growing te m p e ra tu re a s shown i n F ig u re 7.
39
The i n h i b i t o r y e f f e c t s a t each w av elen g th s tu d ie d v a r ie d c o n s id e ra b ly ,
r e s u l t i n g i n th e s i g n i f i c a n t i n t e r a c t i o n s i n T able V„
The g re a te s t . mean' c o l e o p t i l e i n h i b i t i o n was a t 4460 A fo llo w ed
by 4800 A, 4310 A and 4175 A.
A ll o f th e s e w av elen g th s l i e w ith in th e
b lu e re g io n o f th e spectrum (F ig u re I ) .
The g e n e r a l tr e n d was f o r an in c re a s e d c o le o p t ile i n h i b i t i o n a s th e
s h o r te r w av elen g th s were re a c h e d (F ig u re 5 ) .
At 5840 A, th e sh arp
in c r e a s e i n i n h i b i t i o n would su g g e st t h a t t h i s re g io n o f th e spectrum
i s c a p a b le o f re d u c in g th e c o l e o p t i l e e lo n g a tio n a t low en erg y l e v e l s .
These d a ta c l e a r l y show th e i n h i b i t i n g e f f e c t t h a t l i g h t has upon th e
c o l e o p t i l e s o f Karmont w in te r w heat.
The amount o f p r e - i r r a d i a t i o n g e rm in a tio n i s a ls o an im p o rtan t
f a c t o r i n th e i n h i b i t o r y e f f e c t o f th e w av elen g th s u p o n .th e
c o l e o p t i l e s (F ig u re 6 ) .
The g r e a t e s t re s p o n se s R e su lte d from th r e e
and f i v e days g e rm in a tio n .w ith th e fo u r day g e rm in a tio n showing th e
l e k s t e f f e c t . .. T his- would ,su g g est t h a t . a t t h i s p a r t i c u l a r s ta g e of
d e v e lo p m e n t,. th e s e e d lin g s became l e s s l i g h t s e n s itiv e th a n a t th e
t h r e e and f i v e day g e rm in a tio n p e r io d s ,
t
mi±c2
40
SUMMARY
L igh t o f a l l s p e c t r a l r e g io n s s tu d ie d has an i n h i b i t i n g e f f e c t
'"tipon th e c o l e o p t i l e s o f Karmont w in t e r w heat,
■i
At growing tem peratures o f 45° F, th e o v e r a l l e f f e c t was a
g en era l i n h i b i t i o n in th e c o l e o p t i l e le n g t h s o f th e i r r a d i a t e d p la n t s
o v er th e dark tr e a tm e n t,
le n g t h means.
No s i g n i f i c a n t d i f f e r e n c e e x i s t e d among wave­
The fou r day germ ination mean was s i g n i f i c a n t l y lower
than th e th r e e and th e f i v e day means.
There were no s i g n i f i c a n t d i f f ­
e r e n c e s among th e exposure tim e means.
S t a t i s t i c a l l y s i g n i f i c a n t d i f f e r e n c e s e x i s t e d between th e dark
treatm en t and w avelen gth s a t th e 68° F, growing tem p eratu re.
The
s t a t i s t i c a l l y s i g n i f i c a n t d i f f e r e n c e between the 6400. A r e g io n and
th e 4175 A, 4310 A, 4460 A and th e 4800 A reg io n shows t h a t th e
b lu e l i g h t i s more i n h i b i t i n g than red l i g h t a t th e i n t e n s i t i e s
o b ta in ed in th e s tu d y .
The th r e e and f i v e day germ ination means
were s t a t i s t i c a l l y s i g n i f i c a n t l y d i f f e r e n t than th e fou r day
germ ination mean.
The one and two day exposure tim es were
s i g n i f i c a n t l y d i f f e r e n t than th e t h r e e day exposure tim e.
Almost p a r a l l e l re s p o n se s to th e w avelen gth s s t u d ie d were
o b ta in e d f o r th e 45° F, growing tem perature and th e 68° F= growing
tem perature w ith th e 68° F, showing th e g r e a t e s t c o l e o p t i l e i n h i b i t i o n
r e s p o n se .
4
41
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