EFFECTS OF PHYSIOLOGICAL QUALITY OF SEEDS
ON TOTAL GERMINATION, RATE OF
GEMINA‘I’ION. AND SEEDLING VIGOR

Thai: for the Degree of M. 5.
MICHIGAN STATE UNIVERSITY
LioneI V. Websiar
1960

ml...
in

SE

 

   

 

L I B R A R Y
Michigan State
University

 

EFFECTS OF PHYSIOLOGICAL QUALITY OF SEEDS
ON TOTAL GERKINATION,RATE OF GERMINATION,

AND SEEDLING VIGOR

by

Lionel V. Webster

AN ABSTRACT

Submitted to the College of Agriculture
Michigan State University of Agriculture and
Applied Science in partial fulfillment of

the requirements for the degree of

EASTER OF SCIENCE

Department of Farm Crops

1960

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Lionel V. Webster

lb
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This study was undertaken to investigate lurther the
effects of a decline in the physiological quality of seeds
on total germination, rate of germination, and particularly
the vigor of the resulting seedlings.

Barley, beans, corn, and wheat seeds (also alfalfa to
a limited extent) were subjected to various types and amounts
of abuse after which germination tests were conducted. In—
jury was inflicted by mechanical beating, high drying temp-
eratures, and storage at high relative humidities for vary-
ing lengths of time.

The effects on total percentage germination, rate of
germination, and vigor as measured by the average seedling
weight was found to depend both on the type of seed involved
and the nature of the abuse to which they were subjected.

No close correlation was found between these measurements,
or between any of these measurements and the tetrazolium test.

Injury to barley was detectable first by a reduction
in the rate of germination, whereas, injury to beans caused
a reduction in total germination first. In general, the
seedling weight was reduced first in injured corn, and the
rate of germination first in injured wheat.

It is suggested that the characteristic or measurement
that is known to be affected first in a given type of seed

could be used as a measure of the quality of the seed.

EFRECTS OF RRYSIOLOGICAL QUALITY OF SEEDS
ON TOTAL GERMINATION,RATE OF GERMINATION,

AND LEDLING VIGCR

by

Lionel V. Webster

A THESIS

Submitted to the College of Agriculture
Michigan State University of Agriculture and
Applied Science in partial fulfillment of

the requirements for the degree of

MASTER OF SCIENCE

Department of Farm CrOps

1960

\(f‘

N)

5 \.

ACKNOWLEDGMENT

 

The author wishes to express his sincere
appreciation to Dr. S.T. Dexter for his guid-
ance and interest in this investigation, and
also for his valuable advice and assistance
during the preparation of this manuscript.

The author is deeply grateful to his wife,

Lois, for her encouragement and the typing of

this manuscript.

L.V.W.

TLBLE OF C OZTI‘EI‘ITS

LI ST OF IT;‘~BLES O O O O O O O O O O O O O O O O 0

LIST OF FIGURES . . . . . . . . . . . . . . . . .

INTRODUCTION . . . . . . . . . . . . . . . . . .

LITERATURE

I.

II.

III.

JEVIEW
General . . . . . . . . . . . . . . .

Factors Affecting Seed Viability and
Vitality O O O O O O O O O O O O O O .

Tests for Seed Viability and Vitality

METHODS AND MATERIALS

I.

II.

III.

IV.

V.

VI.

RESULTS

I.

II.

III.

IV.

DISCUSSION

SUI‘EE .1"; RY .

CONCLUSIONS

Seeds Used . . . . . . . . . . . . . .
Seed Treatments . . . . . . . . . . .
Germination Tests . . . . . . . . . .
Fungicidal Treatment . . . . . . . . .
Replications and Sample Sizes . . . .

Measurements . . . . . . . . . . . . .

Preliminary Experiments . . . . . . .

Experiments with Mechanically Injured
seed 0 O O O O O O O O O O O O O O O .

Experiments with Heat Injured Seed . .

Experiments with Storage Injured Seed

LITERATURE CITED 0 O O O 0 O O O O O O O I O O 0

ii

iii

ll

13
13
15
17
17
18

19

Table

II.

ii

LIST OF‘TABLES

Analysis of variance of corn germination
test 0 O O O O O O O O O O O O O O O O O 25

The effects of injury on total germina-

tion, rate of germination, average seed-

ling weights, and tetrazolium test

ratings . . . . . . . . . . . . . . . . . AS

iii

LIST OF FIGURES

 

Figure Page

1. A comparison of the effects of mechanical
injury on different types of seed. . . . 31

2. A comparison of the effects of heat injury
on different types of seed. . . . . . . . 31

3. The effects of injury on corn seedlings
grown from treated and untreated seeds. . 32

b- The effects of various types of injury
on wheat seedlings . . . . . . . . . . . 32a

5. A comparison of the effects of storage
at 75 per cent relative humidity on
different types of seeds . . . . . . . . 38

6. A comparison of the effects of storage at
86 per cent relative humidity on different
typ’es Of seeds 0 o o o o o o o o o o o o 38

7. Barley - A comparison of the effects of
injury on total germination, rate of

germination, and average seedling weight. ED
8. Beans - A comparison of the effects of

injury on total germination, rate of

germination, and average seedling weight ho

9. Corn - A comparison of the effects of
injury on total germination, rate of
germination, and average seedling weight M2

10. Wheat - A comparison of the effects of
injury on total germination, rate of
germination, and average seedling weight h2

ll. Tetrazolium test on corn seeds injured
in various ways . . . . . . . . . . . . . E3

12. Tetrazolium test on bean seeds stored
for different lengths of time at 86 per
cent ROI-.1. O O O O O O O O O O O O O O O 0 [l3

13. The effects of storage at high relative
humidities on barley seedlings . . . . . Ah

INTRODUCTION

 

"good" seed is at the

It has long been recognized that
very foundation of good agriculture. Seed of high quality
must have high genetic and physiological quality in addition
to being well processed mechanically.

Plant breeders have been able to improve the genetic
quality of most of the agricultural crops and Industry is
constantly supplying Agriculture with more efficient machin-
ery for harvesting and processing crop seeds. While this
progress is highly desirable, it is essential that the im-
portance of the physiological quality of seeds not be over-
looked.

Environmental conditions can modify or change the phys-
iological quality of a seed at any time between the formation
of the embryo on the parent plant and the germination of that
seed when placed under conditions favorable for germination.
It is extremely important, then, to know how "alive" seeds
really are before they are planted. (Everson, 17, Moore, 25.)
This means that information is needed on the "vitality" as
well as the viability of the seeds. While this need has
been recognized, there is as yet no generally applicable,
easy, and quick method of determining the vitality of seeds.
In most of the work that has been done with the storage and
viability of seeds, percentage of germination has been used

as the sole measure by which to make comparisons between seed

lots. It may be that the vigor of the seedlings after

-2-

emergence would be a better criterion of the quality of the
seed than the percentage germination per se.

This study was undertaken to investigate further the
effect of a decline in the physiological quality of seeds on
total germination, rate of germination, and particularly the
vigor of the seedlings. The tetrazolium "vigor" test was

also used to a limited extent.

LITERATURE .EVIEW

 

I. GENERAL

 

In an historical sketch Brown (9) points out that seed-
testing as a service to those who wished to know something of
seed quality was first undertaken in Denmark and Germany in
1869. In the United States little progress was made in this
field until 1876 when Dr. E. H. Jenkins, on his return from
Europe, emphasized the value of seed-testing.

In an extensive review of the literature dealing with
recent developments in seed technology, Porter (28) states
that while in the early work with seeds the major emphasis
was on seed purity, it was not long until it was recognized
that the measurement of seed viability was of equal import-
ance. It is now generally recognized that the primary pur—
pose of a seed germination test is to determine the ability
of seeds to grow and produce normal plants. This is done
under optimum conditions and has come to be recognized as a
measure of seed viability. Porter (28) points out that many
investigators have compared the laboratory and field germina-
tion of seeds, and that the results seem to indicate that
there is a close correlation between laboratory and field re-
sults only if the field conditions are favorable for germina-
tion.

In order to bring uniformity into the evaluation of
seedlings that result from laboratory germination tests the

Association of Official Seed Analysts and the United States

-3...

"LL'

Department of Agriculture have adopted the following defi-
nition of germination: "In seed laboratory practice, ger-
mination is defined as the emergence and development from
the seed embryo of those essential structures which, for the
kind of seed in question, are indicative of the ability to
produce normal plants under favorable conditions."

The real purpose of seed testing, according to Isely
(23), is to determine the planting value of seed. This value
is determined not only by viability, but also by the vigor of
the seedling.

Working with flower seeds, Heit (21) found that seed
"vitality" was an equally or sometimes a more important fac-
tor in field seedling stands and eventual flower performance
than the actual percentage of laboratory germination.

" as the sum total of all seed

Isely (22) defines "vigor
attributes which favor stand establishment under unfavorable
field conditions. He feels that a vigor test should be prog-
nosticated in terms of field conditions which are critical
with respect to the seed kind involved. Vigor in the field,
he states, is primarily a function of the seed-micro-organism
inter-relationship.

The "vigor of life", Moore (25) states, is at its great-
est level when the seed first matures. After maturity, how-

ever, life becomes less and less vigorous as the never-ceasing

aging process moves onward toward death.

II. FACTOPS AéFECTING SEED VIABILITY AND VITALITY

 

Boswell gt _l (7) state that at a given temperature, the
moisture content of the seed determines its longevity and that
the moisture content in turn depends on the humidity of the
surrounding air.

Working with vegetable seeds they found that deterio-
ration of any one kind of seed at one temperature was, in gen-
eral, proportional to the humidity of storage, or the moisture
content of the seed. Different kinds of seeds responded very
differently to any specific humidity level or moisture content
of the_seeds, and to temperature of storage.

Barton (1) and Barton and Crocker (2) found, in addition,
that seeds of high initial vitality were much more resistant
to unfavorable storage humidities and temperatures than were
those of low initial vitality. The deterioration of a seed
lot, once initiated, proceeded rapidly to the death of all
the seeds under unfavorable storage conditions, but was not
marked under favorable conditions.

From work with tomato seeds stored for 13 years under
dry conditions at -SOC, Barton and Garman (3) concluded that
storage conditions had a greater effect on the seedlings than
the age of the seed.

Tervet (32) working with soybeans found that the per-
centage of seeds infected by fungi (especially Aspergillus

spp.) increased as the moisture content of the seed increased,

-5-

-6-

and that the viability and vigor of the high-moisture con-
tent seed, (above about 13 per cent) rapidly decreased. In
addition, it was found that severe retardation in seedling
growth resulted from storage conditions favoring the develop-
ment of fungi, but that fungicidal treatment of the seeds at
the time of planting improved the vigor and stand of plants.

Dungan and Koehler (15) found that aging, under good
storage conditions, markedly reduced the prevalence of vi-
able fungi in infected seed corn. Despite this decrease in
viable fungi, they found that plants from old seed lacked the
vigor of plants from new seed.

Moore (25) states that even under favorable conditions,
as seeds advance in age, (a) they germinate over a longer
time, giving rise to seedlings of uneven size; (b) the per-
centage germination decreases; (c) the seedlings lack some-
what in vigor and grow slowly; (d) the percentage of abnor-
mal seedlings increases, and (e) more seedlings succumb to
disease.

Of the possible reasons that have been suggested for
the fall in vitality of seeds in dry storage, Crocker (12,13)
and D'Amato (1h) consider the accumulation of substances in
the seed which are toxic to the delicate mechanism of the cell
nucleus and/or the gradual degeneration of the nuclei of the
cells of the embryo as being the most likely.

D'Amato (lu), in critically reviewing the literature

-7-

on the physiological and genetic aspects of seed aging, pre-

sents the

l.

2.

He

following facts;-

Seedlings from aged seeds may show one or more
of the following aberrations:

(a) Necrosis of the meristems (particularly
of the radicle),

(b) Production of adventitious roots from
the hypocotylar and/or epicotylar
regions,

(c) Inability to form chlorophyll,

(d) Precocious death of some seedlings due,
either to some physiological defect, or
to some possible action of toxic metabo-
lites formed during the aging process,
and made soluble at germination.

Observed structural changes in the meristems are
mostly of a chromosome type. A sharp increase
in the rate of chromosome aberrations generally
parallels a sharp decrease in seed germinability.

Autotoxic, automutagenic, toxic or mutagenic

actions may be exhibited by extracts of aged
seeds.

gives the following as evidences supporting the idea

of an "upset of the nuclear mechanism"-

(a)
(b)

(C)

(d)

the occurrence of mutations during dormancy,

the reactions of the shoot and radicle apices
of the embryo to the "mutation-inducing con-
ditions" paralleled by an identical behavior
of the same organs during irradication of dor-
mant fresh seeds;

the established occurrence of mutagenic com-
pounds in aged seed, and

the relationship between the increase in muta—
tion frequency and the decrease in seed germina-
bility.

-8-

In germinating hybrid seed corn under "cold test" con-
ditions, Neptune (27) found wide differences between samples
of the same hybrid produced by different seed-growers. He
felt that a small seed-producer with limited mechanical pro-
cessing equipment was capable of producing seed with a better
cold-test performance than larger seed-growers with a more
highly mechanized process.

Funk (19) reporting on studies conducted at the New
Jersey Agricultural Experiment Station, states that mechani-
cal injury to seed corn may cause reduced yield in the next
year's crop. Most of the variation in yield (58 per cent)
in the tests that were conducted was found to be associated
with seed injury, even though all the seed had been treated
with a fungicide. Pericarp injury in eight commercial lots
of hybrid seed corn that were examined was found to range from
25.5 per cent to 99.5 per cent.

Solorio (30), working with pea bean seed, found that in
all of the kl strains of beans used, the percentage mechanical
damage varied inversely with the level of seed moisture. It
was concluded that the abnormalities in the seedlings, as well
as the differences in germination, vigor, and average weight
per plant from seeds from the three levels of moisture, and
those of the control, were to be attributed to mechanical
injury. The number of normal seedlings and the percentage
germination of the beaten seeds decreased as the content of

seed moisture decreased.

-9-

Working with methyl bromide as a fumigant, Cobb (10)
found that different kinds of crop seeds varied consider-
ably in their reactivity with it. Generally the seedlings
from fumigated seed appeared to be normal, differing from
the unfumigated controls only in their slower emergence and
slower growth rates.

Zavitz (3h), in summarizing his work with different
seed sizes of various annual crops, states that in every
instance the larger seed produced more vigorous seedlings
and a greater yield. The differences were significant when
the same weight of seed was used and were much greater when
the same number of seeds was used per acre.

In a report on the influence of seed size on seedling
growth and yielding capacity of plants, Brenchley (8) states
that field experiments indicate that with annual plants, at
least, better crops are usually obtained by the use of heavy
seed in preference to light, whether equal numbers of bushels,
or equal numbers of seeds are sown per acre. The efficiency
index falls gradually as the weight of the seed rises, and
with prolonged periods of growth, this tends ultimately to
counter-balance the advantage gained by plants from the heav-
ier seeds. With annual crops, however, harvesting generally
occurs before the equilibrium is reached, leaving the advan-
tage with the heavier seeds.

Working with alfalfa, Erickson (16) found that germina-

tion, seedling vigor, and seedling weight were all directly

-10-

associated with seed size, but that plants produced from
initially weaker seedlings tended to overcome this disad-
vantage in about four months' time.

Black (5), using different sizes of subterranean clover
seed, found that when plants were spaced so as to eliminate
competition, the dry weights of the plants were proportional
to seed weights. He found the same to be true during the
early part of the season for plants grown in swards, but when
the swards reached a leaf area index of about h (total leaf
area equalled four times the soil area) a reduction in growth
rate occurred. This critical leaf area index was reached
first by large seed swards. Thus, there was a period in
which the dry weights came to parity so that on the final
sampling occasion there was no significant difference between
the dry weight of the swards from the three seed size groups.
(This assumes no competition from weeds or other species).

From a study of the development and fate of individual
plants grown from contrasting seed sizes in swards, Black (6)
found that where mixed (large and small) seed was used, there
was a steady drop in the number of plants (about 30 per cent)
over the whole period, and that only plants from small seeds
died. The proportion of leaf area held by the small seed
plants and the amount of incident light energy they absorbed
dropped considerably during the growing period. It was con—
cluded that the disappearance in the mixture of the plants

from small seed was due to shading from large seed plants.

III. TESTS FOR SEED VIABILITY AND VITALITY

 

Svien and Isely (31) state that ordinary germination
tests made under favorable conditions do not always suffice
to detect differences between seed lots. Lots with approx-
imately the same percentage germination may differ markedly
in their ability to grow under adverse conditions, and hence
in their agricultural value.

Working with heat damaged barley, French (18) found that
amylose formation in the isolated embryo was indicative of
viability. The amount of amylose formed in a given time
(8 hours) was found to be roughly prOportional to the fresh
weight of the seedlings, to the increase in fresh weight of
the seedlings, and to the seedling height at five days.

Moore (25) suggests the use of (a) the cold test, (b)
germination speed, and (c) the vacuum treatment prior to
testing, as possible aids in determining vigor. From his
work with the cold-test germination of hybrid seed corn,
Neptune (27) found that the association between cold-test
germination and seedling vigor was inconsistent, and that
the correlations of germination and seedling vigor with
yield and maturity did not indicate that there was any con-
sistent relationship among these characteristics.

Moore and Smith (26) state that while low germination
frequently indicates seed weakness, seed vigor is more dif-
ficult to ascertain and at best can only be roughly estima-

ted. The cold test, they feel, gives a fairly good indi-

-11-

-12-

cation of the probable field performance of a seed lot.

The tetrazolium test is claimed by Porter (28) and
Moore and Smith (26) to be superior to other tests employ-
ing dyes or reducible salts, and they feel it has consider-
able practical application. The latter state that tetra-
zolium not only points out which seeds are alive, but also
points out the trouble spots in both live and dead seeds.

It divides the seeds into three classes - (a) the good, live
seed, (b) weak or damaged seeds that will grow in the labora-
tory but not in the field, and (c) the aged, injured, or dis-
eased seeds that can never grow.

Cobb (11), working with seeds that had been fumigated
with methyl bromide, found that the tetrazolium test did not
show the decline in viability during fumigation or in post
fumigation storage.

It was found by Bennet and Loomis (h) that tetrazolium
did not give accurate results when used on freshly frozen
immature corn, but that freezing damage could be determined
if tests were made after the corn had been stored for some
time after freezing.

Rice (29) states that the tetrazolium test was effec-
tive in evaluating the vigor of naturally aged corn seed
after unfavorable storage, but that it was unsatisfactory
as a vigor test on mechanically damaged seed stored under

unfavorable conditions.

MATERIALS AND METHODS

 

I. SEEDS USED

 

In this study the following types and varieties of
seeds were used:
(a) Ranger Alfalfa
-(b) Hudson and Moore Barley
(c) Michelite Pea Beans
(d) Hybrid Corn - ( i) Double cross - Mich. A25
(ii) Single cross

(WF9 x OH 51A)

(e) Genesee Wheat

Some of the seed lots were obtained from the University
farm and others from the Michigan Crop Improvement Association.

In some of the eXperiments the seed lots were used as
they were and in those instances the comparisons were between
different lots. In most of the experiments, however, a seed
lot was divided into several samples which were then treated

in different ways before being germinated.

II. SEED TREATEENTS

 

The treatments used were ones which are known to in-
jure seeds under ordinary farming conditions, namely, mechani-
cal abuse, storage at high relative humidities, and high dry-
ing temperatures. The purpose of this study was not to in-
vestigate these treatments per se, but the treatments were
used to provide material with various types and varying
amounts of injury so that a study could be made of the effects

-13-

‘1U‘

of the injury on the percentage and rate of germination, as

well as the vigor of the resulting seedlings.

A. Mechanical Injury

 

Mechanical injury was inflicted by putting the seed
samples through a "beater" which was used by Solorio (30)
to mechanically injure pea bean seeds. The amount of abuse
was varied by putting the seeds through the beater a varying
number of times and at various speeds. In the case of beans,
corn, and wheat, only seeds which showed no visible injury
were used in the germination tests. It was not possible to
detect injury to the barley seed because of the presence of
the palea and lemma. The palea and lemma on most of the
seeds, however, were damaged extensively and seeds showing
this damage were used in the germination tests.

The designation "Beaten x 6F" indicates that the sample
was put through the beater six times at the fastest of the

"S" indicates

three speeds used (approximately 1000 r.p.m.).
the slow speed (500 r.p.m.) was used, and "M" that the inter-

mediate speed was used (750 r.o.m.).

.L

B. Heat Injugy

 

Some samples of barley, corn, and wheat were dried at
different temperatures in an oven in the Farm Crops Labora-

tory. The drying temperatures ranged from hOOC to 70°C.

-15-

C. Storage Injury

 

Storage injury was caused by storing samples of seeds
in two five-gallon containers at different relative humidities.
The seeds were placed in cheese-cloth bags and hung from the
lids of the containers. Samples were removed after 7, 15,
and 19 weeks.

A relative humidity of approximately 75 per cent was
maintained in the one container by placing beakers contain-
ing a saturated solution of sodium chlorate (NaClO3) in the
bottom of the container. In the other container a saturated
solution of potassium bisulfate (KPSOM) was used to maintain

a relative humidity of approximately 86 per cent.

III. GERMINATICN TEST°

 

The germination tests were conducted in a germinator,

in soil in plastic flats in the laboratory, and in the field.

A. Germinator Tests

 

Samples of seeds germinated in the germinator were
placed either on moist blotters in small plastic crispers
(h$" x b5" x 1%") or rolled in moist blotters and stood at

an angle in dishes containing a little water.

B. Field Tests

 

Most of this research was conducted during the fall
and winter and therefore only a limited number of field ger-

mination tests were possible. Rows 50 inches long and five

—16-

inches apart were used. A hundred seeds were used per row
for alfalfa and barley, and 50 seeds per row for corn and
beans. The corn and beans were planted approximately 1%
inches deep, the barley, % inch deep, and the alfalfa, %

inch deep.

C. Laboratory Soil Tests

 

It was felt that conditions less favorable for germina-
tion than those provided by the germinator were desirable,
and therfore the major portion of the germination tests was
carried out in soil in plastic flats (ll" x 7%" x 2%") in
the laboratory. The beans and corn were planted approxim-
ately 1 inch deep and the barley and wheat % inch deep. To
prevent rapid drying out of the soil in the dry atmosphere
of the laboratory during the winter months, the flats were
placed in plastic bags until germination was complete. The

temperature in the laboratory fluctuated between 73° and 780F.

D. Cold Test

 

The cold test method was used to a limited extent.
Seeds were planted in soil in plastic flats and after the
flats had been put in plastic bags, they were placed in a
cold chamber at hOOF for seven days. At the end of the
seventh day the flats were placed on the laboratory desks

and germination took place at room temperature (approxim-

ately 7SOF).

-17-

E. Tetrazolium Tests

 

In addition to the germination tests, 2, 3, 5 - tri-
phenyl tetrazolium chloride was used to find what agreement
existed between the germination tests and the tetrazolium
test. It was hoped that the tetrazolium would also give
some indication of the nature and/or site of the injury in
the seeds.

A 0.1 per cent solution of 2,3,5 triphenyl tetrazolium
chloride was used for testing barley, corn, and wheat. A.
1.0 per cent solution was used for beans. The seeds were
soaked in water for approximately 15 hours before being sub-
jected to the test. After soaking, the grains were bisected
longitudinally and one half of each kernel was placed in the
tetrazolium solution for h5 minutes at MOOC. The readings
were then made. The beans were left in the solution for four
hours at hOOC, after which the seed coats were removed and the

readings made. (Grabe and Delouche, 20).

IV. FUHGICIDAL TREATMENT

 

Seeds used in germinator tests and in field tests were
not treated with a fungicide. Seeds for about half the lab-
oratory soil tests were treated with "Orthocide 75". This
was done in order to try to eliminate some of the secondary

damage caused by pathogens.

V. REPLICATIONS AND SAMPLE SIZES

 

Two replicates were used for tests conducted in the ger-

-18-

minator. In the laboratory soil tests, two to four repli-
cates were used and four to six replicates were used in the
field germination tests.

In most of the experiments 50 seeds per sample were
used. In some cases, however, 100 seeds were used and in a

few cases 25 seeds were used.

1-. 11“] 4 V“) ' .1‘,
i" I. . ..._ | l
V I . l';UJiLSUR L4)“.1_J JITS

 

A. Germination

 

The seedlings that had emerged at certain intervals
during the germination period were counted in order to det-
ermine the "rate" of emergence of the different samples. The
final count was made at the time the plants were harvested

and the percentage germination was then calculated.

B. Vigor

At an arbitrarily set time the seedlings were harvested
and the fresh weight obtained. In some of the preliminary
experiments the weights of the whole plants were obtained as
well as those of the aerial portions. In some experiments,
in addition to obtaining the total weights, the seedlings
were weighed in groups of ten or twenty according to size.

Throughout this study the average seedling weight was

used as a measure of vigor of the seedlings.

RESULTS

I. PRELIMINARY EXPERIMENTS

 

A. Alfalfa

 

A number of different lots of Ranger Alfalfa seed were
used in an attempt to find out if there was a correlation be-
tween the germination percentage and the weight of the re-
sulting seedlings.

The germination tests were carried out on moist blot-
ters in plastic crispers in the germinator. The results did
not show as wide a range in germination percentage as it was
hoped they would. Because of this and also the fact that
the different lots contained widely differing amounts of hard
seed, the results were inconclusive, and alfalfa was not used
extensively in later experiments.

One experiment was conducted in which three seed lots
were separated into four seed sizes by means of hand screens.
The results showed a correlation between seed size within a
lot and the weight of the seedlings, but not between the per—
centage germination and weight of the seedlings or seed size.
In each of the three lots the largest seeds produced the larg-
est seedlings.

Working with alfalfa, Erickson (16) found that germina-
tion as well as seedling weight was directly associated with

seed size.

-19-

-20-

B. Corn

Five lots of seed (not Mich. h25 or (WF9 x OH 51A))
ranging from one to seven years in age were used in a ger-
mination test carried out in the germinator. These lots
showed marked differences in rate of germination and seedling
weight even though the lowest germination percentage was 87
per cent.

Samples from the same seed lots were also used in a field
germination test. A wide variation in rate of germination and
weight of seedlings was again obtained, but in this experiment
the germination percentage varied from to to 96 per cent. Al-
most optimum germination conditions prevailed during the test.

It was recognized that some of the differences obtained
both with the corn and alfalfa could have been due to variety,
or the conditions under which different lots were produced,
and not to aging or physiological deterioration. Therefore,
it was decided that for all further experiments, comparisons
would be made between differently treated samples of the same
seed lot. The germination percentage, rate of germination,
and average seedling weights were then calculated as percent-

ages of the controls.

C. Comparison of Measurements

 

The weights of the whole plants and of only the aerial
portions were obtained for bean samples grown in the field. A
high correlation (+96) was found between these measurements.

Because of this high correlation and the correlation between

-21-

different measurements on corn seedlings found by Rice (29),
it was decided to use only the weights of the aerial portions
of the seedlings in making comparisons between differently
treated samples.

In a number of experiments the seedlings were arranged
in order according to size and weighed in groups of 10 or 20
(from 50 or 100 original seeds). A correlation of from .75
to .90 was found between the weights of the size groups of the
control and corresponding size groups of the various treat-
ments. A high correlation (.90 for corn) was also found be-
tween the average weight per 10 seedlings and the weight of
the ten largest seedlings.

In the presentation of the results of this study, all
comparisons between treatments were made on the basis of av-
erage seedling weight. This average weight was obtained by
dividing the total weight of seedlings by the number of seed-

lings that emerged.

II. EXPERIMENTS WITH MECHANICALLY INJURED SEED

 

A. Germination Tests

 

Alfalfa - Several samples of three different seed lots
were put through the mechanical beater a varying number of
times. These seeds were then germinated on blotters in plas-
tic crispers in the germinator, along with samples of unbeaten
seed.

The results showed no significant reduction in seedling
weight whereas there was a considerable increase in both per-
centage germination and rate of germination for the most sever-
ely beaten samples. It seems apparent that the beater, in-
stead of damaging the seed, acted as a scarifier and reduced

the percentage of hard seed in the samples.

Egglgy - Several samples of a 1958 Hudson Barley seed
lot were mechanically beaten up to 12 times at the "fast”
speed. The damage was so extensive that it was necessary to
use some seeds that showed visible damage to the palea and
lemma. It was not possible to ascertain whether or not the
seed itself had been injured.

Samples that had been beaten four, six, eight, and
twelve times were germinated in flats in the laboratory. When
the first count of seedlings was made, it was found that the
rate of germination from some of the beaten samples was higher
than that of the control. (See Figure 7A, page hO.)

The beating had no detrimental effect on the percentage

-22-

-23-

germination. The different beating treatments caused some
variation in the average seedling weights for different sam-
ples, but there was no definite decrease in average weight.
(See Figure 1, page 31.)

A sample that had been beaten six times and then ger-
minated in the germinator was found to be equal to the control
in percentage germination, rate of germination, and average
seedling weight. Some of the same seed was used in a field

germination test and similar results were obtained.

B3325 - Samples from several different seed lots were
beaten. The amount of visible injury suffered by different
samples was inversely related to the moisture content of the
seeds at the time of beating. (Solorio, 30). Only seeds
showing no visible injury were used in the germination tests.

The germination tests were carried out in flats in the
laboratory. The rate of germination of the dry samples was
reduced considerably by beating. Samples that had been stored
at 86 per cent relative humidity for seven weeks and then beaten
showed an improvement in rate of germination. (See Figure 8A,
page MO.)

The percentage germination was reduced considerably by
mechanical injury. The average weight of seedlings fell sig-
nificantly also, but not to the same extent as the percentage
germination. (See Figure 1, page 31.) The number of abnor-

mal seedlings increased with an increase in mechanical injury.

-2u_

Germination tests conducted in the germinator showed similar
but less marked differences while field tests showed more

marked differences.

gggfl - Samples from two seed lots which had been in dry

storage were beaten four, six, and eight times respectively.

In addition, a sample that had been stored for seven weeks at

75 per cent relative humidity was beaten six times and one that
had been stored for seven weeks at 86 per cent relative humidity
was beaten four times.

Germination tests carried out in flats in the laboratory
showed that beating generally had little effect on either the
percentage germination or the rate of germination. In the
case of seed stored at 75 per cent relative humidity for seven
weeks and then beaten, the percentage germination was reduced
to 88 per cent of that of the control. For the same sample
the average seedling weight was reduced to 66 per cent of that
of the control. The seedling weights for the other beaten
samples, except the one beaten only four times, were reduced
approximately the same amount. (See Figure1fl page 31.) Ger-
mination tests carried out in the germinator and in the field
showed essentially the same results.

Tests carried out with seeds that had not been treated
with a fungicide showed wider differences than those where
treated seeds were used. " Secondary injury from pathogens was
probably responsible for some of the reduction in vigor of

.seedlings from beaten seed. (See Figure 3, page 32.)

-25-

Three samples that had been mechanically injured were
included in a cold test in which half of the replicates were
treated with a fungicide (Orthocide 75). The results were
very similar to those obtained in the other germination tests.
The treated replicates showed an increase in average seedling
weight over the untreated, but the percentage germination was
not affected by the fungicidal treatment. These results were
analysed statistically and it was found that there were highly
significant differences both between treated and untreated, and

between the controls and the mechanically injured samples.

 

 

 

TABLE I
ggggg§;§_ 93 ygglgygg 93 CORN GERMINATION TEST
Total 19 16.88 - -
Beatings u 8.33 2.08 6.80%
Treatments 1 b.37 b.37 lh.28*
Beatings x Tr. h) 3.5M) - -
Error 19:. _;égj_ _ _
lb n.28 .306

Ehggt - Samples of wheat were beaten four, six, eight,
and twelve times. Germination tests were carried out in flats
in the laboratory using only seeds which showed no visible in-
jury.

The mechanical injury had no noticeable effect on the

rate of germination. The percentage germination was rather

-26-

variable, but the average seedling weight was reduced sig-
nigicantly by mechanical injury to the seeds. Beating the
seed four and twelve times reduced the average seedling weights

to 8h and 70 per cent, respectively, of that of the control.

B. Tetrazolium Test

 

Mechanically injured corn could be distinguished from
the control by the lighter red color of the embryo of the in-
jured seed, but it was not possible to determine either the
extent or the site of the injury by the tetrazolium test.

The tetrazolium test was used to compare two samples
of seed which had been subjected to the same amount of beating,
but, in the one case, the beating had been done four months be-
fore the test, and, in the other case, only a few days before
the test. No difference was found between the two samples,
but they could both be distinguished from the controls. (See
Figure 11, page U3.)

It was impossible to distinguish between mechanical and
heat injury by the tetrazolium test. Storage injury gave a
wide variation of coloration within a sample and, therefore,
could be distinguished from other types of injury by this lack
of uniformity within a sample.

The results of tetrazolium tests carried out on mechani-
cally injured wheat were very similar to those with corn.
Beaten barley samples, however, could not be distinguished from
the controls. This fact lends support to the suggestion that

the barley seeds were, in fact, not injured.

-27-

Mechanically beaten bean seeds which showed no visible
injury were subjected to the tetrazolium test. They stained
a dark red and could not be distinguished from the controls on
the basis of color. However, when the seed coats were removed
at the time the readings were made, it was found that the coty-
ledons were broken into a number of pieces and, in many cases,
the cotyledons were broken off of the embryos.

The injury in the case of the beans appears to have
been purely mechanical, while in the case of corn and wheat,

it was, atleast partly, physiological.

III. EXPERIMENTS WITH HEAT INJURED SEE

 

A. Germination Tests

 

Barley - Samples of a single barley seed lot with an
initial moisture content of 15 per cent were dried at 50°C,
600, and 70°C respectively. The seeds were germinated in
plastic flats in the laboratory about three months after
drying.

The results showed that high drying temperatures re-
duced the percentage germination, rate of germination, and
average weight of the seedlings significantly. (See Figure
2, page 31, and YB, page hO.)

9232 - Samples of four different corn seed lots were
dried at temperatures between hOO and 70°C. The initial
moisture content of the lots ranged from 18 per cent to 30
per cent. The seed lots with the highest initial moisture
contents were injured the most by the higher drying temper-
atures.

The results from germination tests conducted in the
germinator and also in flats in the laboratory showed that
increasing the drying temperature sharply reduced percentage
germination, rate of germination, and the average weight of
the seedlings. (See Figures 2, page 31, and QB, page A2.)

Under both laboratory germination conditions and cold
test conditions treatment of the dried samples with a fungicide

did not have any effect on the percentage germination or the

-28-

-29-

vigor of the seedlings. This would seem to suggest that sec-
ondary injury from the presence of pathogens was not involved
in the dried samples as was the case with mechanically injured

samples. (See Figure 3, page 32.)

Ehggt - Samples of a single wheat seed lot with an ini-
tial moisture content of 15 per cent were dried at 50°, 60°, and
7000 respectively. Germination tests were carried out in
flats in the laboratory about three months after the samples
had been dried. The results show that the drying temperature
appeared to have more effect on the rate of germination of the
wheat than on that of the barley. See Figures 7B, page AC,
and 103, page b2.)

. A drying temperature of 70°C was not as injurious to
wheat as it was to barley and corn under the conditions of.
this experiment. The correlation between the decrease in ger—
mination percentage and the decrease in average weight of the
seedlings was not as high for wheat as it was for barley and

corn. (See Figure 2, page 31.and figure 8, page 32a.)

B. Tetrazolium Test

 

With barley, corn, and wheat it was possible to dis-
tinguish between the seeds dried at high temperatures and the
controls by the lighter red color of the embryos of the dried
seeds. It was not possible by the use of the tetrazolium test

to determine the site of injury, nor to distinguish between

heat injury, and mechanical injury. (See Figure 11A, page A3.)

-30-

Description of Treatments Shown in Figure l

 

Barley and Wheat

 

Bians

Corn

2.
h.
6.
8

.rrm

Beaten
Beaten
Beaten

Beaten

Stored
Stored
Stored
Stored
Beaten

Beaten

Beaten
Beaten
Stored

Beaten

 

at 86% R.h. for 7 weeks, then beaten x 2F
at 8 % B.H. for 7 weeks, then beaten x AF
at 75% R.T. for 7 weeks, then beaten x 1F
at 75% n.F. for 7 weeks then beaten x 2F

x 1F

x 2F

x hF

x 6F

at 75% R.H. for 7 weeks, then beaten x 6F

x 8

#1.]

 

 

Percentage of Control

Percentage of Control

100

90

80

70

60

So

ho

30

20

 

10

100

90

80

7O

60

50

no

30

20

 

10

A
Average Weight of Seedlings

    

‘\
\..

\ O
‘ ~
\\ ~
\ I Hum-Q.~‘§‘-
I s
\ I ‘1'
t I
V’

Ber ley ——
3.“. 0.--..-
Corn —--—
Inset —"—

ala l Lin
1 2 3 u 5 £> 7

Amount of Abuse

cab

-3

JJ

1-

100

90

80

70

60

50

no

30

20

10

Total Germination

 

\
\
b \
\
\
\
p \
\
\
\
P \
\
\
b ‘ I
\/ \‘
\
-
‘b

1 Ala I ll

 

j I a
1 2 3 h 5 6 7 8
Amount of Abuse

Figure 1. A comparison of the effects of mechanical injury on
See opposite page for details of

different types of eeed.
the amount of abuse.

A
Average weight of Seedlings

 

 

n
505 65h
Drying Temperature

70

100

90

80

7O

60

50

no

30

20

10

B
Total Germination

 

 

1 n
50° 60° 70°
Drying Temperature

Figure 2. A comparison of the effects of neat injury on different
types of seed. Drying temperatures given in degrees Centigrade.

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3
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-33-

IV. EXPERIMENTS WITH STORAGE-INJURED SEED

 

A. General

 

Barley, beans, corn, and wheat were used in these ex-
periments. Samples from the same lots of seeds were placed
in both the 75 per cent and 86 per cent relative humidity stor-
age containers. Small samples were removed at the end of 7,
15, and 19 weeks respectively. These were air-dried and placed
in airtight containers similar to those used for all other sam-
ples used in this study.

In some cases germination tests were carried out soon
after the samples had been dried, while in others the samples
were kept in dry storage for as long as three months before
tests were carried out. All the germination tests were car-

ried out in flats in the laboratory.

B. Germination Tests

 

Barley - Storage at 75 per cent relative humidity for
as long as 19 weeks had no effect on either percentage germina-
tion or rate of germination. The average weight of the seed-
lings, however, increased with storage up to 19 weeks. (See
Figure 5, page 38.)

Storage at 86 per cent relative humidity caused a grad-
ual decrease in germination so that after 15 weeks the percent-
age germination was only 66 per cent of that of the control.
After 19 weeks it was 75 per cent. This apparent improvement

could probably be accounted for by the fact that the 19-week

_34-

samples were germinated within ten days of their removal from
storage, whereas the 15-week samples had been stored dry for
approximately 5 weeks.

The average weight of the seedlings increased by 12 per
cent with storage for 15 weeks at 86 per cent relative humid-
ity. After 19 weeks of storage, the average seedling weight
was almost equal to that of the control. (See Figure 6A, page
38.) Rate of germination decreased with increasing length of
time in storage at 86 per cent relative humidity. (See Figure

7C, page 80.)

EEEEE - Storage at 75 per cent relative humidity for as
long as 19 weeks had no apparent effect on percentage germina-
tion or average weight of seedlings. (See Figure 6, page 38.)
The rate of germination decreased slightly with increased stor-
age time up to 19 weeks.

The effects of storage at 86 per cent relative humidity
were noticeable after 7 weeks in storage, and were very marked
after 15 weeks. At the end of the 19th week in storage ger-
mination percentage was zero.

The percentage germination decreased more rapidly than
the average seedling weight. After 15 weeks in storage, ger~
mination was only 3 per cent of that of the control, while the
average seedling weight was 55 per cent of that of the control.
(See Figure 6, page 38.) After 7 weeks in storage at 86 per
cent relative humidity, the rate of germination was reduced

slightly. (See Figure 88, page ho.)

-35-

£233 - Storage at 75 per cent relative humidity had
practically no effect on the percentage germination or the rate
of germination. The average seedling weight was reduced
slightly, being 93 per cent of that of the controls after 19
weeks in storage. (See Figure 6, page 38.)

Seeds showed a considerable reduction in the rate of
germination when stored for 15 or 19 weeks at 86 per cent re-
lative humidity. The percentage germination also decreased,
dropping to 83 and 85 per cent of that of the control after 15
and 19 weeks respectively. On the other hand, the average
weight of the seedlings remained equal to that of the controls
even after 19 weeks in storage. (See Figures 6, page 38, and

90, page ME.)

flhgat - The rate of germination was increased slightly
by storage at 75 per cent relative humidity for as long as 15
weeks, and after 19 weeks in storage it was approximately equal
to that of the control. The percentage germination increased
to 8 per cent above the control with storage for 15 weeks.
After 19 weeks, it was still h per cent above the control.
(See Figure 58, page 38.)

Storage for 7 weeks at 75 per cent relative humidity
increased the average weight of seedlings 12 per cent above
that of the control. After 15 weeks it had dropped to 97
per cent, and after 19 weeks, to only 92 per cent of that of

the control. (See Figure 5A, page 38.)

-36-

The percentage germination of seed stored at 86 per cent
relative humidity was reduced very sharply. It was 60, 26,
and 22 per cent of that of the control after 7, 15, and 19 weeks
in storage, respectively. The decrease in percentage germina-
tion and rate of germination was much more rapid than the de-
crease in average seedling weight. (See Figure 6, page 38, and
10C, page h2.) After 7 weeks in storage at 86 per cent rel-
ative humidity, the average weight of seedlings did not show
any decrease, but after 15 weeks, it had dropped to 81 per cent
of that of the control, and after 19 weeks it was 8h per cent.

(See Figure 6A, page 38.)

B. Tetrazolium Test

 

In these experiments the tetrazolium test was employed
in order to try to determine the site and extent of injury
caused by poor storage conditions.

The test was used on barley, beans, corn, and wheat
seeds, but no definite staining pattern was found that would
indicate the site of injury.

Bean seeds showed unstained or dead tissue in the rad—
icle and/or the cotyledons. Seeds which had been stored for
15 weeks at 86 per cent relative humidity showed a very wide
range of coloration. (See Figure 128, page A3.)

With corn stored for 19 weeks at 86 per cent relative
humidity, a wide range of coloration was found also, but it

was not possible to detect definite dead areas. The number

-37-

of seeds which had begun to deteriorate was much smaller than
in the case of beans. This could explain the fact that the
average weight of corn seedlings remained equal to that of the
control while the percentage germination dropped to 85 per cent
for seeds stored at 86 per cent relative humidity for 19 weeks.
(See Figure llB, page 83.)

Tests on barley and wheat gave results very similar to

those obtained with corn.

Percentage of Control

Percentage of Control

 

A B

 

 

 

 

 

 

 

 

Average Weight-of Seedlings Total Ge;mination
0’ \
"/ ‘\/ (‘-’.o‘ I ~.~\..
100%---‘v ~\ 100 .‘afl:heg—e ‘.e”“
as. 5------ ‘s.”‘ -w
‘0‘. ~.. ‘
\. .*‘
90. 90.
D
80... 80 ..
70- 70 I-
60L 60 ..
50- 50 I-
no- no.
3 Barley — 30 p
Beans —--——
Corn —e_
2 wheat --—- 20 p
10 l I l )0 a J a
7 15 19 ‘ 7 15 19
Weeks in Storage leeks in Storage
Figure 5. A comparison of the effecte of etorage at 75 Per cent
relative humidity on different types of eeeda.
A 2
Average Weight of Seedlings Total Germination
100
90
80
70
60
So
no
\ e
30 ,. Barley — 3 \ \
Beane ------ ‘\ ‘ \
COP!) _'_ “ \ --~
20 p “halt —.-_ ‘ 2 \‘
\ ‘x
a
10 . . j. 1 . ‘ ‘
7 15 19 7 15 19
Weeks in Storage weeke in Storage
Figure 6. A comparieon of the effecte of etcrage at 86 per cent

relative humidity on different typee of eeede.

D cr'xtion

(D

U)
I .1
P71

 

Barley

Mechanical Abuse

 

1. Beaten
2. Beaten

x HF

x 6F

3. Beaten x 12F

Drying Temperatures

 

1. 50:0
2. 6000
3. 70 0

Weeks ip_Sto§§ge
l. Stored

2. Stored
3. Stored

at 75
at 86%.
at 86

for
for
for

of Treatments_§hown in Figure 7

 

19 weeks
7 weeks
19 weeks

 

Description of Treatments

Beans

 

Mechanical Abuse

1. Stored
beaten

2. Stored
beaten

3. Beaten

Weeks in Storage

1. Stored
2. Stored
3. Stored

at 86%
x 2F

at 75%
x 1F

at 7
at E
at i

T.‘
e

5
D

mtngj

L113:

for

for

for
for
for

Shown in Figure 8

7 weeks then

7 weeks then

15 weeks
7 weeks
15 weeks

Percentage of Control

Percentage of Control

A

Mechanical Injury Storage Injury

   

 

 

 

 

 

 

 

110 110 110
90 9O 9O
80 I 80 801
70> 70 70
60, 60 60
50 p 50 50
0.. no no
u Total Germ. -...
Rate of Germ. --—-
30 Av. Seedling Wtr-—- 30 3o_
20[ 4 s a 20 a L L 20 a a a
l 2 3 l 2 3 l 2 3
Amount of Abuses Drying Temperatures» Ieeks in Storagev

Figure 7. Barley - A comparison of the effects of injury on total
germination, rate of germination, and average seedling weight.

a. 3!
Mechanical Injury Storage Injury

11

 

 

‘i‘otal Germ. ......
Rate of Germ. ——
Av. Seedling lt.---

    

..

“~e

 

 

 

6 \ .
‘ |
I
5 ‘.
s
‘.
h x
|
O
3 ‘. \
e
I
2 a 2 a ‘11 a
1 2’v 3 1 2 3
Amount of Abuse# Ieeke in Storagee

Figure 8. Beans - A comparison of thJ effects of injury on total
germination, rate of germination, and average seedling weight.

sBee opposite page for details

-u1_

Descrigtion of ireatments Shown in Figure 9

 

 

 

 

 

 

Corn
Mechanical Abuse
1. Beaten x AF
2. Beaten X 6?
Drying Tegperatures
o
l. SOOC
2. 600C
3. 70 C
Weeks in Storage
1. Stored at 75% B.H. for 19 weeks
2. Stored at 86% R.E. for 7 weeks
3. Stored at 86% R.H. for 19 weeks
Description of Treatments Shown in Figure 10
Wheat

Mechanical Abuse

 

1. Beaten x DP
2. Beaten X 6F
3. Beaten x 12F

Drving Temperatures

1. 50:0
2. 60 C

3. 7000

Weeks in Storage

 

l. Stored at 7:1 B.H. for 19 weeks
2. Stored at 86% R.H for 7 weeks
3. Stored at 8o% R.H. for 19 weeks

Percentage of Control

Percentage of Control

-ug-

A B C

    

 

 

 

 

 

 

 

Mechanical Injury Heat Injury Storag: Injury
llO: 110
l 100
90
80
70
m.‘ 60
50.. so
hd» “0
Total Germ. .....
Rate of Germ. _
31 Av. Seedling Ute—~— 30
2 _ + l j 20 1 2 7 1
1 2 3 3 1 3 3
Amount of Abuses Drying Tenperaturese leeks in Storagee

figure 9. Corn - A comparison of the effects of in ury on total
germination, rate of germination, and average a ling weight.

A E 2
Mechanical Injury Heat Injury Storage Injury

 

to Total Germ. ......
Rate of Germ. .-—-——-
30 Av. Seedling It 4———

20 l 20 A A a
7 1 Q 1 1 2 3

Amount of Abuseo Lrying Temperaturesc leeks in Storagec

 

 

 

 

 

?igure lO. lheat - A comparison of the effects of injury on total
germination, rate of germination, and average.seedling weight.

oSee opposite page for details

\J‘HS‘WNH

5'me

 

1. 2. 3. h. S.
A.

Stored at 86% R.H. 19 wks.
Beaten x uF-stored h mths.
Freshly beaten x AF

Dried at 55°C

Control

Range in coloration of
seeds stored at 86% R.H.
for 19 weeks

Figure 11. Tetrazolium test on corn
seeds injured in various ways

 

l. 2. 3. h.

Control

Stored at 86% R.H. 7 wks.
Stored at 86% R.E.lS wks.
Stored at 86% R.H.l9 wks.

Range in coloration of
seeds stored at 86% R.H.
for 15 weeks

Figure 12. Tetrazolium test on bean seeds stored
for different lengths of time at 86 per cent B.H.

-hb-

 

l. 2.

1. Stored at 86% R.H. 19 weeks
2. Control ’
3 Stored at 75% R.H. 19 weeks

Figure 13. The effects of storage at high
relative humidities on barley seedlings

-u5_

TABLE

 

II

*M“

THE EFFECTS OF INJURY ON TOTAL GERHINATION, RATE

Gsamimarlou,
IUA TEST RATINGS.
PEBCENTAGES or

Control

Dried at 60°C

Stored
Stored
Stored

Stored

at 75%
at 75%
at 86%

at 86%

Beaten x 8F .

Control

Beaten x 2? .

Stored at 75%

Stored at 86%

.H. for 15 wks.
for 19 wks.
.F. for 15 wks.

for 19 wks.

AVERAGE SEEDLING WE

 

 

 

 

R.H. for 19 wks.

for 19 wks.

 

 

TEE MEASUREMENTS ARE GIVEN AS
CONTROL
LCORN
Average
Germination Seedling
Total Rate Weight
. . . 100 100 100
. . . 101 28 8k
100 100 93
100 115 93
83 36 100
85 26 99
. . . 99 9t 60
B. BE HS .
. . . 100 100 100
. . . l7 5 59
lO'u 9 97
O 0

OF

IGHTS, AND TETRAZOL-

Tetra—
zolium
22E:

100
8b
97
55
68
52

52

100

83
27

DISCUSSION

 

The purpose of this investigation was to examine the
relationships between the total percentage germination and
the other characteristics relating to germination in seeds
that may have suffered some type of injury. To simplify the
discussion, the nature of each test may be listed briefly as
follows:

I. Total percentage germination or number of
seedlings.
II. Rate or relative rapidity of germination.

III. Vigor or size of seedlings as indicated by
weight.

IV. Vigor as indicated by tetrazolium tests.

The total germination or the maximum number of seed—
lings from a treated sample was compared to that of the con—
trol. For example, if the control gave 90 per cent total
germination and the treated sample gave 60 per cent, the ratio
of 60 to 90 or 67 per cent was considered the germination val-
ue of the sample.

The rate or rapidity of germination has been taken as
the relative number of seedlings found when one half of the
control sample had germinated. For example, if the curve of
daily germination showed that one half of the seedlings (90/2)
in the control had been produced by the end of 3 days, the

count from the treated lot at the end of 3 days was taken and

-h6-

-u7_

compared with the h5 seedlings of the control. If this num-
ber were 15, then the ratio of 15 to h5, or 33 per cent would
be considered the rate or rapidity of germination of the sample.

The vigor or size of seedlings was obtained by dividing
the total weight of the seedlings from a given treatment by
the number of seedlings from that treatment. The average
seedling weight for the treatment was then expressed as a per-
centage of that of the control.

Seeds that were subjected to the tetrazolium test (See
page 17) were given a rating of 1 to h according to the inten-
sity and pattern of staining. The sum of the ratings for
each sample was compared with that of the control.

To make comparisons more meaningful, the measurements
for each test have been presented as percentages of the con—
trols in Table II, page h5; Figures 1 and 2, page 31; 5 and

6, page 38; and 7 to 10, pages AU, AZ.

Mechanical Injury - Mechanically beating barley had

 

practically no detrimental effect on the total germination,
the rate of germination, or the average seedling weight in
spite of very extensive abrasions. (See Figure 7A, page hO.)
It appears that the palea and lemma protected the seed from
injury, and that the extensive damage to the palea and lemma
reduced mechanical resistance to germination. Toole gt 31
(33) found that the germination of seeds of many grasses,

including barley, was improved by cutting, breaking, acid—

-u8_

treating, or removing certain seed coverings. The tetrazolium
tests did not indicate any injury to the barley seeds.

Bean seeds were found to be very susceptible to mech-
anical injury, particularly in dry samples. In general, to-
tal germination and the rate of germination fell off at about
the same rate. The average seedling weight was reduced con—
siderably, but not to the same extent as the rate and total
germination. (See Figure 8A, page MO.) The tetrazolium
test was of no value in determining either the site or extent
of the injury caused by mechanically beating bean seeds.

The response of corn and wheat to mechanical injury was
very different from that of barley or beans. (See Figure 9A
and 10A, page A2.) The total germination and the rate of ger-
mination were only slightly reduced whereas the average weight
of the seedlings was reduced considerably. The increased act-
ivity of pathogens on the injured seed was probably partly
responsible for the reduction in weight of the seedlings.
However, even when a suitable fungicide was used, the differ-
ences were significant. This is in agreement with results ob-
tained by Funk (19) with treated corn seed.

The tetrazolium test on mechanically injured corn and
wheat did not indicate the site of injury and differed from
the control only in the intensity of the red coloration. It
did appear, however, to give a fairly accurate indication of
the vigor of the seedlings as measured by the average seed-

ling weight. (See Table II, page AS, and Figure 11A, page h3)

-Lg-

Heat Injury - The average seedling weight of barley

 

which had been dried at high temperatures showed a more rapid
decline than either the total germination or the rate of ger-
mination. (See Figure 73, page MO.) Corn showed an almost
simultaneous decline in all three measurements. (See Figure
98, page LB.)

The tetrazolium test on heat-injured corn gave results
which showed a close correlation with the average seedling
weight. (See Table II, page LS.) It is felt, however, that
additional work should be done in this area in order to verify
the existence of a close correlation between these two meas-
urements.

It was possible to distinguish between storage injury
and heat injury in both corn and wheat by the tetrazolium test.
Heat-injured seeds showed a uniform light coloration while
storage-injured seeds showed variability in intensity and pat-
tern of coloration. Mechanical injury also gave a uniform
light coloration and therefore could not be distinguished from

heat injury. (See Figure llA, page M3.)

Storage Injury - The results from these experiments in—

 

dicate that storage at high relative humidities for a limited
period improved the total germination, the rate of germination,
and the average seedling weight. The partial hydration of

the seeds apparently stimulated enzyme activity, (Mayer &
Anderson, 2h) and although this activity was halted again when

the seeds were placed in dry storage, they seemed to have been

-50-

left in a state of "preparedness". When these seeds were
placed under conditions which were favorable for germination,
they were apparently not only able to germinate more rapidly,
but were also able to utilize their reserve food supply more
efficiently and produce larger seedlings.

Continued storage at high relative humidities beyond
this period of "stimulation" resulted in a rapid decline in
the rate of germination of seeds of barley, beans, corn, and
wheat. The total germination of barley, beans, and wheat
declined almost as rapidly as the rate of germination. (See
Figures 70 and BB, page L0, and 100, page M2.) The total
germination of corn did not decline as rapidly as did the
rate of germination. (See Figure 90, page h2.)

The average seedling weight for barley, corn, and wheat
was reduced only slightly by storage for as long as 19 weeks
at 86 per cent relative humidity. (Figure 6A, page 38.) The
average seedling weight of beans declined almost as rapidly
as the total germination. It seems, therefore, that the ef-
fects of prolonged storage at a high relative humidity can be
detected first by its effect on the total germination and the
rate of germination. (See Figures 7-10, pages to, h2.)

When the tetrazolium test was applied to seeds that had
been stored at high relative humidities, it was found that
they showed a wide range i6 coloration and staining patterns.
This was especially noticeable with the beans. (See Figures

118 and 12B, page M3.) Some seeds stained a bright red and

-51-

could not be distinguished from the controls, whereas others
failed to stain at all. Between these extremes there were
some showing definite dead areas. Some samples which still
contained some seeds that appeared equal to the controls were
shown by a germination test to have zero germination. This
suggests that the process of deterioration had probably al-
ready begun in the seeds which appeared to be equal to the
controls. It also suggests that once this process of det-
erioration sets in, it proceeds rapidly to the death of the
individual seed. This idea was suggested previously by
Barton (1). Where storage damage was less severe the ger-
mination test showed that the seeds were actually of a higher
quality than the tetrazolium test indicated. (See Table II,
page #5.)

The more rapid decline in total germination than in av-
erage seedling weight could be explained by the fact that seeds
within a given sample do not all begin this process of deter-
ioration at the same time, and until they do begin to deterio-
rate, their vigor probably remains approximately equal to that
of the controls. Thus, early death of weak seeds improved
the average vigor of the survivors.

In the case of corn, the tetrazolium.test consistently
indicated that the quality of the seed was lower than the ger-
mination tests showed it to be. (See Table II, page AS.)
These results are not in accordance with those of Rice (29)

who found that the tetrazolium test was effective in evaluating

-52-

the vigor of naturally aged corn seed after unfavorable stor-
age.

From this study it is apparent that seeds vary widely
in their response to different types of injury. The results
also show that no one measurement gave a complete and accurate
indication of the quality of the seed or its agricultural
value.

Although no general and invariable correlation was
found between the total germination, the rate of germination,
the average seedling weight, and the tetrazolium test, it
seems that injury may be indicated by its effect on one or
more of these measurements.

The total germination, rate of germination, and seedling
weight are all closely related to the agricultural value of
seeds. A decline in one or more of these characteristics is
undesirable, and indicates that the process of deterioration
has begun. It is possible to have a relatively high total
germination and have seedlings that lack vigor, as was the
case with mechanically injured corn and wheat. (See Figure 1,
page 31.) It is possible, also, to have a low total germina-
tion and have seedlings with excellent vigor as was the case
with storage-injured barley, corn, and wheat. (See Figure 6,
page 38.) On the other hand, total germination, rate of
germination, and average seedling weight all fell off rapidly
with heat injury in barley, corn, and wheat. (See Figures

78, page hO, and QB and 108, page b2.) Beans also responded

-53-

in this way with mechanical and storage injury. (See Figure
8A and B, page hO.)

When the total germination is reduced before the average
seedling weight, it would be possible to compensate for this

f a percentage germination test by increasing

to

6

O

U)

with the u

I

u

the rate of s

(D
L

ding. Such compensation would not be possible,
however, when the average seedling size is reduced before the
total germination.

In evaluating the quality of seed, it would be helpful
to know which characteristic or measurement was affected first
by injury. The results obtained in this study suggest that

it might be possible to ascertain whether total germination,

rate of germination, or seedling weight is reduced first in
a given type of seed. For example, in injured barley the

rate of germination was reduced first and/or most rapidly for
all three types of injury. With injured beans the total ger-
mination was reduced first. In general, the seedling weight
was reduced first in injured corn, and the rate of germination
first in injured wheat. Thus, in general, poor or injured
seed is first recognized in barley and wheat by glgw germina-

tion; in beans by low percentage germination; and in corn

 

by small seeding size. Various exceptions will be seen in

 

Figures 7 to 10 on pages DO and hZ.)
It is suggested that a more accurate indication of the

true "planting value" of seeds could be obtained if informa-

-5L;_..

tion regarding the characteristic or measurement affected
first by injury in a given type of seed were considered in

addition to the standard germination test.

SUHMARY

In this study, barley, beans, corn, and wheat seeds,
and to a limited extent, alfalfa seeds were used. Different
seed samples were subjected to various amounts of mechanical
abuse, different drying temperatures, or different lengths
of time in storage at high relative humidities.

Germination tests on the "treated" samples and their
controls were carried out chiefly in flats in the laboratory
with a limited number being carried out in a germinator and
in the field.

The total germination, rate of germination, and average
seedling weight was determined for each sample. These measure-
ments were then calculated as a percentage of the corresponding
measurement of the control in order to make the comparisons
more meaningful.

The tetrazolium test was used to a limited extent so
that results from this test could be compared with the re-

sults obtained from the germination tests.

-55-

CONCLUSIONS

 

The following are the conclusions that have been drawn

from this study;

1.

The types of seeds differed widely in their re-
sponse to abuse.

Various types of injury had different effects
on a given type of seed.

No close correlation was found between any of
the measurements used.

Total germination in many cases did not give an
accurate indication of the quality of the seeds.

The average seedling weight appeared to be a
good index to the vitality of mechanically in-
jured seed.

The rate of germination in some cases gave a
fairly accurate indication of the reduction in
vitality.

The tetrazolium test gave evaluations of qual-
ity which varied considerably, both above and
below those of the average seedling weight.

The characteristic or measurement that is known
to be affected first in a given type of seed
could be used as a measure of the quality of
the seed.

-56-

10.

LITERATURE CITED

 

Barton, Lela V., Relation of Certain Air Temperatures
and Humidities to Viability of Seeds. Contri.
Boyce Thompson Institute, 12285-102, 19h1.

 

Barton, Lela V., and William Crocker, Twenty Years 9;
Seed Research at Boyce Thompson Institute for
Plant Research. Farber and Farber Ltd., London,
19US.

 

 

 

Barton, Lela V., and Helen R. Garman, Effect of Age
and Storage Condition of Seeds on the Yield of
Certain Plants. Contri. Boyce Thompson Insti-
tute, iu:2u3-2u5, l9h6.

 

Bennet, Norah, and W. E. Loomis, Tetrazolium Chloride
as a Test Reagent for Freezing Injury of Corn
Seed. Plant Physiology, 2h:162-17u, 19h9.

 

 

Black, J. N., Seed Size as a Factor in the Growth of
Subterranean Clover (Trifolium Subterraneum L.)
Under Spaced and Sward Conditions. Aust. Jour.

Agri. Res., 8:335-351, 1957.

 

 

, Competition Between Plants of Different
Initial Seed Sizes in Swards of Subterranean
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and the Light Micro-climate. Aus. Jour. Agri.
Res., 9(3), 299-318, 1958.

 

 

 

Boswell, Victor R., E. H. Toole, Vivian K. Toole, D. F.
Fisher, A Study of Rapid Deterioration of Vege-
table Seeds and Methods for its Prevention.
U.S.D.A. Tech. Bull. 708, 19uo.

 

Brenchley, Winifred E., Effect of Weight of Seed Upon
the Resulting Crop. Ann. pf App. Bot., 10:223—
2hO, 1923.

 

Brown, E., Development of Seed Testing. U.S.D.A. Bur.
P1. Ind., Div. Cer. Crop§_and Dis., Mim. Circ.,
1939.

 

 

 

Cobb, Rodney D., The Effects of Methyl Bromide Fumiga-
tion on Seed Germination. Proc. Assoc. Offic.
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-57-

ll.

12.

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lb.

15.

l6.

19.

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-58-

Cobb, Rodney D., 2,3,5 - Triphenyl Tetrazolium Chlor-
ide as a Viability Indicator of Seeds Fumigated
With Methyl Bromide. Proc. Assoc. Offic. Seed
Aggly, h6:62-6, 1956.

 

 

Crocker, William, Life-span of Seeds. Bot. Rev. h:235-
27b, 1935-

, Growth of Plants. Reinhold Pub. Corp-
oration, N.Y., 19MB?-

 

 

D'Amato, Francesco, On Some Physiological and Genetic
Aspects of Seed Aging. A Contribution to the
Problem of Aging and of Spontaneous Mutability
in Plants. Caryologia, 6:217-2h0, English
Summary, pp. 237-2h0, 195R.

 

Dungan, George H., and Benjamin Koehler, Age of Seed
Corn in Relation to Seed Infection and Yielding
Capacity, figyon. Jour., 36thh3, 19Lh.

 

Erickson, Lambert C., The Effect of Alfalfa Seed Size
and Depth of Seeding Upon the Subse uent Pro-
curement of Stand. Agron. Jour., 3 :96u-973,
19M-6 o

Everson, L. E., What Kind of Seed Did You Get? Iowa
Farm Science, Vol. 10, No. 1, p. 9,10, July,
1955.

French, Richard 0., Formation of Embryo Starch During
Germination as an Indicator of Viability and
Vigor of Beat—damaged Barley. Plant Physiology,
3u:500-505, Sept., 1959.

 

 

 

Funk, C. R., Injury to Seed Can Lower Corn Yields.
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Grabe, Don F., and James C. Delouche, Rgpid Viability
Tests. A Progress Report, 1959, State College,
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Heit, C. E., Laboratory Germination and Vigor as Com-
pared to Soil Tests and Field Performance in
Flower Seeds, Proc. Assoc. g: Offic. Seed
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Isely, Duane, Vigor Tests. Proc. Assoc. Offic. Seed
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-59-

Isely, Duane, Employment of Tetrazolium Chloride for
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Assoc. Off. Seed Anal., h2:lh3-153, 1952.

 

 

Meyer, Bernard, 5., and Donald B. Anderson, Plant Physio-
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Moore, R. P., Life Alone is not Enough - How Alive are
Life Seeds? Seedman's Digesty Sept., 1955.

 

Moore, R. P., and E. Smith, Seed Must be More Than Just
Alive. Crpps and Soils 9(6):1h-16, M1, 1957.

 

Neptune, Gerald, Cold Test Germination of Hybrid Seed
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Bot. Rev., 15(u/5>=221-3uu. 19u9.

 

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