OTHEsts‘

 
    
   

LIBRARY
fiichigazz State
University

 

This is to certify that the
thesis entitled

RESPONSE OF HIGH MOISTURE ONION SEEDS TO STORAGE
WITH DESICCANTS IN A SIMULATED TROPICAL

ENVIRONMENT AND SEED PRIMING
presented by

Syed Md. Monowar Hossain

has been accepted towards fulfillment
of the requirements for

Ph. D. degree in fiQLtiquiure

fl/Za

Major professor

August 6, 1984 Hugh C' ”we

 

Date

 

MS U is an Affirmative Action/Equal Opportunity Institution

  

_. -r? 4

 

 

 

 

 

 

Ill! ll! ll‘lllllllllllllllllfllll

3 1293 01109 3873

 

 

AIVIESIHJ RETURNING MATERIALS:
Place in book drop to
LIBRARIES remove this Checkout from
w your record. FINES WI”

 

 

 

be charged if book is
returned after the date
stamped below.

 

M o 9 m

 

 

RESPONSE OF HIGH IOISTUEE ONION SEEDS TO STORAGE
'ITH DESICCANTS IN A SIIULATED TROPICAL

ENVIRONNENT AND SEED PRIIING

By

Syed Nd. Ionovar Hoaaain

A DISSERTATION
Sublitted to
Michigan State University
in partial fulfillment of the requirements
for the degree of
DOCTOR OF PHILOSOPHY

Depart-ent of Horticulture

1984

ABSTRACT

RESPONSE OF HIGH MOISTURE ONION SEEDS TO STORAGE
WITH DESICCANTS IN A SIMULATED TROPICAL
ENVIRONMENT AND SEED PRIMING

By
Syed Md. Monowar Hossain

Silica gel, activated alumina, calcium sulfate
(Ca804) and calcium chloride (CaClz) at two doses (3,

2:) dried high moisture (14.5% w.b.) onion (Allium 2gp; L.)
seeds to 4.1 to 7.3% moisture. High vigor and viability
were maintained when the seeds were stored with desiccants
for 7 months (harvesting to next planting) in airtight
plastic bottles at 30°r1°C and 75r5$ RH.

High moisture onion seeds with 92$ initial
germination completely lost their viability after 4 months
of storage. Seeds stored with desiccants emerged 80 to 86%
at 10° and 82 to 87% at 20°C following 7 months of
storage. Time to 50$ seedling emergence (T50) was faster
(7.7 to 8.4 days) at 20° than 10°C (16 to 16.6 days).
There was no significant variation in seedling growth rate
in different treatments. The higher dose (2:) of each
desiccant produced more abnormal seedlings than the lower

dose (1) at both 10° and 20°C.

Syed Md. Monowar Hossain

There was greater leakage, as measured by electric current
flow. from seeds stored at 2: than from seeds stored at 1
dose of each desiccant. The greatest leakage of solutes
occurred from high moisture seeds after 7 months of
storage.

None of treatments except the dry control, activated
alumina (x), and silica gel (x) reduced the vigor and
viability of onion seeds stored in airtight plastic bottles
for 14 months.

Priming (-11 bars mannitol at 10°C for 8 days)
improved vigor of seeds accelerated aged at 30°C and 75$
RH for 7 and 8 weeks. However, seeds accelerated aged for
5, 6, and 9 through 12 weeks did not respond to priming.
After priming, seeds stored for 7 months emerged faster at
both 10° and 20°C but seedling emergence increased only

at 10°C.

To the Memory of my Mother.

who passed on May 14, 1981

ii

ACKNO'LEDGMENTS

It is my pleasure to express gratitude and homage to
Dr. H. C. Price for his guidance and untiring support
throughout my studies at Michigan State University. He
always listened to me with utmost patience even without any
formal appointment. My special thanks to the members of
the guidance committee, Drs. L. 0. Copeland, R. C. Herner,
E. C. Rossman. and H. H. Zandstra for their sincere support
and advice during the entire period of the Ph.D. program.

I appreciate my friends Dan Drost and Rebecca Haughan for
their assistance in analyzing the experiment data by
computer and Dr. H. Mallik for discussion on electrical
conductivity.

I would like to thank my wife Suraiya and son Imrose
for their patience and understanding. I also thank my
father, father-in-law. and other relatives for their
inspiration and encouragement throughout the period of
studies.

Finally. I am grateful to Bangladesh Agricultural
Research Council for awarding me a scholarship under the
'orld Bank Program to complete higher studies in the United

States.

iii

TABLE OF CONTENTS
Page
LIST OF TABLES O O O O O O O O O O O O O O O O O O O 0 '1

LIST OF FIGURES O O O O O O O O O O O O O O O O O O 0 'ii

INTRODUCTION . . . . . . . . . . . . . . . . . . . . . l
REVIEV 0F LITERATURE . . . . . . . . . . . . . . . . . 5
Flowering, Seed Formation, and Morphology . . . . 5
Vigor Concept and Its Measurement . . . . . . . . 7
Viability Concept and Its Measurement . . . . . . 11
Factors Affecting Seed Storage . . . . . . . . . 13
Genetic Makeup of the Seed . . . . . . . . . . l3
Seed Structure and Composition . . . . . . . . 14
Seed Maturity . . . . . . . . . . . . . . . . . 15
Production Conditions . . . . . . . . . . . . . 16
Harvesting and Conditioning . . . . . . . . . . 17
Storage Enrironment . . . . . . . . . . . . . 19
Organisms Associated with Seed Storage . . . . . 25
Changes in Seeds During Storage . . . . . . . . . 27
Methods of Onion Seed Storage . . . . . . . . . . 29

Use of Desiccants in Seed Storage
of Other Species . . . . . . . . . . . . . . . 30
Priming . . . . . . . . . . . . . . . . . . . . . 31

MATERIALS AND METHODS . . . . . . . . . . . . . . . . 35

Moisture Content (i) of Onion Seeds

in Equilibrium with Different Relative

Humidities (RH) at 30°C . . . . . . . . . . . 35
Effect of Different Temperatures at High

Relative Humidity on Vigor and Viability

of Onion Seeds . . . . . . . . . . . . . . . . 37
Determination of Desiccant Dose . . . . . . . . 38
Effect on Desiccants on Drying and Storing of

High Moisture Onion Seeds . . . . . . . . . . 4O
Seedling Emergence Test . . . . . . . . . . . . 42
Rate of Seedling Emergence Test . . . . . . . . 43
Electrical Conductivity Test . . . . . . . . . 43
Seedlings Growth Rate Test . . . . . . . . . . 44
Seedlings Abnormality . . . . . . . . . . . . . 44
Onion Seed Storage for 14 Months . . . . . . . 45

'iv

Page

Priming of Onion Seeds . . . . . . . . . . . . . 45
Accelerated Aged Seeds . . . . . . . . . . . . 45
Stored Seeds . . . . . . . . . . . . . . . . . 48

Statistical Analysis . . . . . . . . . . . . . . 49

RESULTS AND DISCUSSION . . . . . . . . . . . . . . . . 50

Effect of High Humidity and Different
Temperatures on Onion Seeds in Storage . . . . 50
Effect of Desiccants on Storage of High

Moisture Onion Seeds . . . . . . . . . . . . . 53
Seed Drying . . . . . . . . . . . . . . . . . . 53
Seedlings Emergence . . . . . . . . . . . . . . 56
Seedling Growth Rate . . . . . . . . . . . . . 65
Seedling Abnormality . . . . . . . . . . . . . 68
Seed Leachates . . . . . . . . . . . . . . . . 72
Seeds Stored for 14 Months . . . . . . . . . . 76

Effect of Priming . . . . . . . . . . . . . . . . 78
Accelerated Aged Seeds . . . . . . . . . . . . 78
Stored Seeds . . . . . . . . . . . . . . . . . 81

SUMMARY AND CONCLUSIONS . . . . . . . . . . . . . . . 84
APPENDICES O O O O O O O O O O O O O O O O O O I O O O 89
A. Temperature and Relative Humidity During
the Period from April to October
in Bangladesh . . . . . . . . . . . . . . . 90
H. Seed Viability Nomograph for Onion . . . . . 92

BIBLIOGRAPHY O O O O O O O O O O O O O O O O O O O O O 9‘

LIST OF TABLES

Table Page

1. Moisture content (1 wet basis) of onion seeds in
equilibrium with different relative humidities of
aqueous solutions of different H2804
conc.ntr.tion' .t 30'C e e e e e e e e e e e e e e 36

2. Moisture absorption (i of total weight of
desiccant) at 36$ RH and doses (g) of different
d.‘i°°.nt' O O O O O O O O O O O O C O O O O O O O ‘0

3. Seedling emergence (i) at 10° and 20°C and
predicted germination (i) by monograph of seeds
stored for 7 months at different moisture content
‘nd 30.31.c e e e e e e e e e e e e e e e e e e e e 64

4. Effects of desiccants on the dry weight of seedling
from onion seeds stored 7 months in airtight
plastic bottle at 30'21°C and 75t5$ RH . . . . . . 66

5. Correlation coefficient between different variables
of onion seedling emergence at 10' and 20°C . . . . 67

6. Influence of desiccant doses on the abnormality of
onion seedlings (i) after 7 months seed storage at
3o.*1.c .nd 75t5$ in O O O O O O O O O O O O O O 0 1o

7. Moisture content, T50 and percentage of seedling
emergence (20°C) of onion seeds after 14 months
storage at 30°t1°C and 75255 RH in airtight
plastic bottles . . . . . . . . . . . . . . . . . . 77

8. Effect of priming on rate (T50) and ercent
germination of onion seeds aged for 2 weeks
't 75‘ in .nd 30'c O O O O O O O O O O O O O O O O 19

9. Effect of priming of desiccant stored onion seeds
with mannitol solution (-11 bars) on seedling
emergence (S) at 10' and 20'C . . . . . . . . . . . 83

A—l Temperature and relative humidity during the period
from April to October in Bangladesh . . . . . . . 91

vi

Figure

1.

LIST OF FIGURES

Days to 50$ radicle emergence T50) of onion seeds
stored at 10°. 20°, 30°. and 40°C, and at
75‘ RH for 12 '..k‘ 0 O O O O O O O O O O O O O O O

Radicle emergence ($) of onion seeds stored at 10°.
20', 30', and 40°C and 75$ RH for 12 weeks . . . .

Moisture content ($ wet basis) of onion seeds
at each month during 7 months storage of high
.Oi‘tnr. (1405‘) 'ood‘ I O I O O O O O O O O O O 0

Days to 50$ emergence (T50) of seedlings
at 10°C from onion seeds in every month during
7 .O‘th' .tor.‘° e e e e e e e e e e e e e e e e e

Days to 50$ emergence (T50) of seedlings at 20°C
from onion seeds in every month during 7 months
.tor..° O O O O O O I O O O O O O O O O O O O O O 0

Normal versus abnormal seedlings emerged from onion
seeds after 7 months storage with different
desiccants and in dry control . . . . . . . . . . .

Electrical current flow (nA/seed) through leachete
of onion seeds after 7 months storage with and
'ithont d°.1°°.nt' e e e e e e e e e e e e e e e e
Effect of priming of desiccant stored onion seeds
with mannitol (-11 bars) on T50 values at 10°

.nd 20'C e e e e e e e e e e e e e e e e e e e e e

Seed viability nomograph for onion . . . . . . . .

vii

Page

51

52

54

59

61

69

75

82

93

INTRODUCTION

The research topic on storage problems of onion
(A1113; 232; L.) seeds was chosen in the context of
climate, importance of onion crop. and need for a low-cost
seed storage system in Bangladesh. The climate of
Bangladesh is hot and humid from March to October. The
mean temperature is about 29°C and relative humidity (RH)
is 84$ during this period. The winter is mild from
November through February with a mean temperature of
20°C. The average annual rainfall varies from 1193 to
3452mm, depending on the location. About 80$ of the total
rain falls during June to October.

Onion is the third most important vegetable. after
potato and sweet potato, in Bangladesh. It is consumed
fresh as a vegetable, and as a spice, thus there is a great
demand for onion during the entire year. Total production
in Bangladesh was 136,000 tons from 32,000 hectares in
1976-77 (Anonymous, 1979). Onions are cultivated on small
farms during winter from local and foreign varieties.

Onion plants produce good quality seeds in this climate
(Ahmed. 1976). However. after harvesting the high moisture

(14-15$) onion seeds, farmers find difficulty of seed

drying and storage in tropical climate. High moisture
onion seeds cannot be dried to a safe storage moisture
level (6-7$) under the sun and these seeds completely lose
their viability in storage from harvesting to next planting
(April to October) because of high temperature and relative
humidity (Appendix A). Similarly. Delouche et al. (1973)
reported that onion seeds lost their viability completely
within 6 month of storage in tropical environment (30°C

and 75$ RH).

As locally produced onion seeds are not available,
most farmers plant bulbs (780-900 kg/ha) and a few farmers
plant seedlings grown from imported seeds for onion
production. Bulbs planting increases the costs of
cultivation and utilizes a high quantity of otherwise
edible onions. Use of imported seeds requires a
substantial amount of foreign currency, increases
cultivation costs, and creates dependency on other
countries. In addition, the supply of imported seeds to
farmers is sometimes irregular and untimely due to lack of
proper transportation and distribution systems in rural
areas of Bangladesh.

Refrigerated storage for onion seeds is not
available in rural areas due to lack of electricity and may
not be economically sound because of high electricity cost

and poor financial status of the farmers. Therefore. a

simple, inexpensive system is needed for drying and storage
of locally produced onion seeds at ambient high temperature
and relative humidity in Bangladesh.

It was thought that treatment of high moisture onion
seeds with chemical desiccants would replace the need for
mechanical drying and maintain high vigor and viability of
seeds in storage in tropical climate of Bangladesh.
However. the previous works with desiccants on onion seeds
storage (Newhall and Hoff, 1960. Nakamure, 1975) were
limited to CaClz and CaO. Information about the effects
of chemical desiccants on seed vigor is lacking.

Therefore, there is further scope of storing onion seeds
with other desiccants and study their effects on vigor and
viability of seeds.

Vigor of onion seeds stored in tropical climate
might have been reduced to some extent due to the effect
of aging. It has been hypothesized that priming might
improve the vigor of stored seeds by repairing membranes
damage and thus would increase their rate and percent of
germination.

A research project dealing with onion seed storage
with desiccants and priming of stored and accelerated aged

seeds was planned with the following objectives:

To study the effects of CaClz. Ca804,

silica gel, and activated alumina at two
different doses on drying of high moisture
seeds.

To evaluate the vigor and viability of stored
seeds by different physiological and
biochemical tests.

To select the proper kind and dose of desiccant
on the basis of seed storability.

To study the effects of priming on invigoration

of stored and accelerated aged seeds.

REVIE' 0F LITERATURE

FloweringI Seed FormationI and Morphology

Flowering in onion plants is induced by the
interaction of cool temperature and plant or bulb size.
Small bulbs or immature plants show little or no induction
of flowering by cool temperature (Jones and Mann. 1963).
Thompson and Smith (1938) found that when medium sixed sets
of 'Ebenexer' and 'Red Icthersfield' were planted and grown
in greenhouses at 10-15.5°C, both the cultivars bolted
100$. A fairly cool temperature (4.5-14°C) over a
considerable time when parental bulbs are in storage or
overwintering in the field greatly influences the
subsequent flowering of onion plants. Photoperiod has
little effect on the initiation of the onion flower (Jones
and Mann, 1963). The shoot apex ceases to produce leaf
primorda at the time of inflorescence initiation. The
inflorescence of onion is an umbel which is an aggregate of
many small inflorescences (cymes) of 5 to 10 flowers each.
Because the whole inflorescence of common onion consists of
dozens of cymes, the flowers of an umbel open irregularly
over a period of two weeks or longer (Jones and Rose,

1928). This irregular opening of flowers causes variation

in fertilisation and seed development. Since in onion
flowers anthers dehisce before stigma is receptive. cross
pollination is the rule, but interpollimation between
flowers of the same umbel is also frequent (Hayward. 1938).
After fertilisation. the ovule undergoes a series of
physiological, biochemical, antamomical and morphological
changes as it develops into a seed. According to McKay
(1961), seed formation and development in higher plants
consists of six steps: (1) formation of stamens and
pistils in flower buds. (2) opening of flower,
(3) pollination, (4) fertilisation, (5) growth of
fertilized egg and its differentiation and finally.
(6) maturation of the seed. Maturation is complete when
the seed reaches its maximum dry weight. A mature viable
seed symbolizes the multiplication. continuation of
generation, and bearer of inheritance of a plant species.
Onion seed becomes wrinkled and irregular in shape during
its maturation inside the capsule. Botanically, an onion
seed is a mature and fertilised ovule containing an embryo.
endosperm and surrounded by a black seed coat. The embryo
is comprised of a single cotyledon, short stem. shoot apex.
and short primary root. The embryo (6mm long by 0.4mm
diameter) may be crescent shaped or curved into more than a
complete circle (Hoffman. 1933). The embryo which makes up
approximately 1/10 of the bulk of the seed lies embedded in

the fleshy endosperm (Cooley. 1895).

Vigor Concept gag it; Mgggggeggnt

The term 'Triebkraft' meaning both 'shoot strength'
and 'driving force' was originally proposed by Nobbe (1876)
and later it was supported by a plant pathologist in
Germany in 1911, when he observed that cereal seeds
infected by Fusarium disease were capable of germination,
but incapable of penetrating a 30-40mm thick layer of
ground bricks (Hiltmer and Essen. 1911). However, the
concept of 'Triebkraft' was translated into English as
vigor to denote the ability of seedlings to grow rapidly
and normally (Heydecker, 1972). Since then, many
researchers around the world tried to explain the vigor
concept in different ways. It appears from the review of
literature (Heydecker, 1969. 1972. Pollock and Roos. 1972,
Voodstock. 1973, Ching. 1982) that vigor of seed and
seedling is conceptualised many ways such as germination
and shooting power, vitality, strength of germination.
rapidity and uniformity of germination under unfavorable
conditions. survival of seeds upon sowing and emergence of
healthy nermal seedlings. Better stand establishment and
higher crop productivity by withstanding the attack of
diseases, insects, the competition of weeds. and the
environmental stresses. longer storability of seeds under
optimum or adverse conditions are also proposed parameters

of seed and seedling vigor.

Two major seed testing organisations, the
International Seed Testing Association (ISTA) and
Association of Official Seed Analysts (AOSA) proposed
specific definition for seed vigor separately. In 1977
(McDonald. 1980). ISTA defined "seed vigor is the sum total
of those properties of the seed which determines the
potential level of activity and performance of the seed or
aeedlot during germination and seedling emergence?
Similarly in 1979 (McDonald, 1980). AOSA dcfimed"seed vigor
as those seed properties which determine the potential for
rapid uniform emergence and development of normal seedlings
under a wide range of comditionsf

According to McDonald (1980), ISTA's definition is
an academic definition because it attempts to relay what
seed vigor is while AOSA'a definition is an operational one
as it focuses on what seed vigor does. Therefore, more
research and understanding is yet needed to formulate one
universally accepted definition for seed vigor.

The expression of seed vigor is influenced by three
sets of interacting components resulting from (1) genetic
makeup. (2) seed development. harvest. and storage
conditions, and (3) seed germinating environment (Ching.
1982). Further, she stated that seed and seedling vigor
derives from several aspects: (1) an efficient repair and

reactivation of fully preformed systems (e.g.. membrane,

ensynes. proteins). (2) a rapid and sufficient synthesis of
ensynes and organelles for the degradation of reserve food
in supplying substrate for the growth of the seedlings,
(3) a timely depressed genetic information in transcribing
and splicing specific RNA for ensyme and protein synthesis
and most importantly. in replicating DNA for new cells,
(d) an optimum biosynthetic environment in terms of
substrate. energy, water, oxygen, etc. Despite the
disagreement on a definition, there is a strong agreement
on the importance of vigor as a major quality factor of
seed (Abdul Baki. 1980). In explaining the importance of
seed vigor measurement. Grebe (1976) stated that the main
purposes of different vigor tests are to:

a. indicate relative storability of seeds

b. rank the seedlots as per vigor

c. select suitable seedlots for sowing

d. adjust seed rate per unit area

e. indicate stand establishment. uniformity

of seedlings and yield potentiality.

Review of literature (Heydecker, 1972. McDonald,
1975. 1980. Copeland. 1976. Ioodstock. 1973. 1976)
indicates that different tests had been developed to
evaluate the vigor of the seeds and seedlings. These vigor

tests can be grouped under three categories as follows:

10

Physical tests which measure seed
characteristics such as sise, weight. and
density.

Physiological tests which measure some aspects
of germination or seedling growth under optimal,
as well as stress conditions. Stress may
include: cold temperature. super or suboptimal
moisture levels. disease organisms. mechanical
obstruction, and others (Voodstock, 1973). Some
of the physiological tests are: (a) rate of
germination test. (b) cool germination teat. (c)
cold test. (d) accelerated aging test. (f) brick
gravel test. and (g) paper piercing test.
Biochemicals tests measure the biochemical
indices of seed vigor which may be grouped into
four general classes: (1) vital staining
reactions. (2) ensyme activity not measured by
staining reactions. (3) coordinated activity at
the level of subcellular fractions, such as
respiratory and biosynthetic processes, and (4)
measures of membrane integrity (Ioodstock.
1973). According to these parameters. some of
the biochemical tests include: (a) tetrasolium
test. (b) glutamic acid decarboxylase activity

(GADA) test, (c) glucose metabolism test,

11

(d) respiration rate test, (e) ATP level test,
and (f) conductivity test.

However. certain limitations had been imposed on
vigor testing in order to select the most suitable vigor
test. Ideally, a vigor test should be objective,
inexpensive. rapid. uncomplicated. reproducible, and
correlated with field performance (McDonald, 1975. 1980).
None of the current vigor tests meet all their criteria
(Copeland, 1976). But seed quality can be assessed
correctly when vigor tests are used to compliment each
other (McDonald. 1980). There is still no one
internationally accepted vigor test (Heydecker. 1972).
Further intensive research and testing are required before
agreement can be reached on one universally accepted vigor
test that can be commercially used for accurate seed

quality assessment.

Zipbility Concepp pug Ipp Measurpmenp

Viability indicates that a seed is alive and capable
of germination under favorable conditions in absence of any
dormancy. But it is difficult to abide rigidly by a single
definition, sometimes a different definition is more useful
in a particular context (Roberts. 1972a). Moore (1972)
used the term viability in a broad sense. Viability is the
capability of seed to develop into a normal seedling, even

under conditions which may not be entirely ideal.

12

According to this definition, redicle protrusion is
insufficient evidence that a seed is viable. In another
sense. viability denotes the degree to which a seed is
capable of being metabolically active, and possess ensynes
capable of catalysing metabolic reactions required for
germination and seedling growth. In this context. a given
seed may contain both live and dead tissues and may or may
not be capable of germination (Copeland. 1976). Seed
viability gradually declines as the aging continues. But
once seed viability is lost. it becomes irreversible
(Roberts and Ellis. 1982).

Viability is generally measured to assess the
suitability of seed lots for crop production and also for
use by industry, especially the melting of barley (MacRay,
1972). Several authors (Ivar Gadd. 1950, Barton. 1961.
MacKay. 1972, Copeland. 1976) indicate that various tests
are available for viability measurement. These tests are
(l) germination test, (2) tetrasolium test, (3) oxidase
test, (4) peroxidase test, (5) coloring test (indigo
carmine, aniline dyes). (6) selenium and tellurium test,
(7) excised embryo test. (8) conductivity test. (9) x-ray
test, and (10) free fatty acidity test. Except for the
germination test, however, all other tests are indirect

methods of measuring viability (MacRay. 1972).

13

Facporg Affecping Seed Storage
Storage potentiality of seeds is directly or
indirectly influenced by various factors. Review of
literature (Owen, 1956, Harrington. 1972, Justice and Base.
1978) indicates that important factors can be outlined as
follows:
1. Genetic makeup of the seed
2. Seed structure and composition
3. Seed maturity
4. Seed production conditions
5. Harvesting and conditioning
6. Storage environment
a. Seed moisture content
b. Temperature
c. Oxygen pressure

7. Storage organisms

Gen ti Makeu of e S ed

The storage potential of seeds varies among the
species and cultivars due to their genetic makeup (Base,
1979). According to Harrington and Douglas (1970).
groundnuts (Arachis gppogpea L.) and onion seeds lose
germination at a faster rate than maise (2p; ppyp L.) and
tomato (Lppoperpicon eppplenppm Mill.) seeds, respectively,
under the same storage conditions. Inheritance of seed

longevity in storage is well documented among cultivars of

14

the same species. Toole and Toole (1953b) found the
snapbean (Phaseolus vulgarip L.) seeds of cultivar 'Black
Velentine' had a longer life spam that the seeds of
'Brittle wax' after 45 months storage at 25°C, 65$ RH,

and 21°C, 57$ RH conditions. Similarly. Shanda et al.
(1967) reported that barley (Hopdpum vplgpre L.) seeds of
cultivar 'Orderbrucker' had greater resistance to
germination loss than the cultivars 'Traill' and 'X-691-I'

after 11 weeks storage at 23°C with 18$ moisture content.

§eed Structure and Compopipiom

Storage life of many seeds is influenced by seed

structure. for example, oat (Avena papiyg L.) and timothy

 

(Phleum pretense L.) seeds stored with glumes intact had a
longer life span than the seeds without glumes (Lekon.
1954). The increased life span of cereal seeds was due to
suppression of mold growth by the glumes during storage
(Justice and Base, 1978). Other seed structures affecting
seed storage are seed cost. hilum, and micropyle. Bean
seeds possess hilum and micropyle which may permit the
entry or exit of moisture depending on the level of
relative humidity in storage. Under some conditions, the
hilum may become soft or damaged. allowing fungi to enter
the seed (Justice and Base. 1978). Hard impermeable seeds

of different species of genera. (e.g.. Alpigia, Tpigolipp).

have a longer life span because their seed costs are

15

impermeable to water and oxygen. Moisture content of their
seeds does not fluctuate with the changes in atmospheric
relative humidity as do seeds with permeable seed coats
(Bees. 1980). The seed cost impermeebility excludes Oz

and prevents the autoxidation of fatty acids and
concomitant loss of seed viability (Flood and Sinclair.
1981). Seeds contain reserve food materials. primarily as
carbohydrates, fats, and proteins. James (1967) reported
that seeds with a high oil content. e.g.. soybean (filppipe
pp; IL.) Merr.) sealed with 7$ moisture maintained poor
viability. while starchy seeds, e.g.. sorghum (Sorghpm
pipolor [L.] Moench) retained their viability for four
years with 7$ to 10$ moisture at room temperature.
Regarding the influence of protein content on seed
storability. Bittenbender and Rica (1977) reported that
high protein seeds (2.11 mg/seed) of rice (szlp pppiyp L.)
variety IR-5 germinated 14$ after 12 days storage stress at
40°C and 20$ moisture content in airtight vials while the
low protein seeds (1.64 mg/seed) of the same variety
completely lost their viability after 12 days under the

same storage stress conditions.

e M ri
Seed maturity is the point in seed development at
which maximum dry weight is attained (Roberts. 1972). The

more nature a seed when harvested, the greater is its vigor

16

and therefore potential for establishment of a new seedling
(Pollock and Roos. 1972). Eguchi and Tamade (1958)

reported that mature seeds of cabbage (figpgpigp glgrpgpg
var. capitata L.). carrot (Dppppp pppppp L.). cucumber

(Cupumip sppivps L.). radish (Rpphpppp pppizpp L.). Velsh
onion (Allipn fiptulopum L.) maintained viability better
than the immature seeds in storage. The same was true for
Kentucky blue grass (22; pretenpip L.) in which mature
seeds germinated 81$ and immature seeds 59$ after storage
at 32°C and 15$ R.H. for 93 months (Base. 1965). Pollock
(1961) reported that level of maturity of carrot seeds
affected the vigor and viability. Hence. it is logical to
believe that mature seeds have longer storability than the

immature seeds due to their higher vigor potential.

Prpduption Conditions

Veather is possibly the most important production
factor affecting seed viability and storability. In the
warm and humid tropical climates the quality of seed
produced is generally low, and deterioration continues at a
rapid rate during storage (Delouche. 1980).

High humidity favors the growth of fungi on seeds in
the field and this promotes rapid loss of viability during
storage (Bass. 1980). Rains just before harvest can cause

preharvcst sprouting in wheat and consequently a reduction

17

in seed quality and storability (Moss et al.. 1972).
Unfavorable weather during or before harvest influences the
susceptibility of seeds to mechanical injury, which in
turn. affects storage potential. Green et al.. (1966)
reported that delayed harvest of soybean seeds due to
inclement weather caused an increase in mechanical damage
to the seeds during harvest. Such seeds deteriorate more
rapidly in storage than undamaged seeds (Harrington.

1972). A drought during seed development results in light.
shriveled seeds (Delouche. 1980) with reduced storability.
Mineral deficiencies in the soil during seed may also
affect seed storage life. Harrington (1960b) found that
seeds from carrot, pepper (Ceppicum ppppg L.) and lettuce
(Laptpca pativa L.) plants severely deficient in K and Ca
lost their germination more rapidly during three to eight
years storage at room temperature than seeds from plants

given a balanced nutrition (N. P. R and Ca).

H r e in an Condi i nin

Mechanical injury causes a kind of mutilation
resulting from harvesting. conditioning and handling
operations. Seed injury symptoms may be of different
forms: (a) gross damage to seed coat such as splits and
cracks. (b) internal damage. (c) microscopic break,
especially of seed cost. or (d) cryptic damage which is

possibly physiological in nature (Copeland, 1976). The

18

most extensive and intensive injuries reduce viability of
seeds immediately. Small injuries do not have an immediate
effect on viability but become critical as aging occurs in
seeds (Moore. 1972).

Resistance to mechanical damage varies among
cultivars as well as species. Thus flax (Liggg
pgipgpipgimpm L.) seeds are more resistant than sesame
(Spppmpm ingicum L.) seeds (Moore. 1972) and cultivars with
colored seeds are more resistant than white seeded
cultivars of snapbean (Atkim. 1958). Physical conditions
of the seeds such as sise. shape and moisture content
influence the mechanical damage. According to Moore (1972)
small seeds are more resistant than large seeds. e.g.. lime
been (Phageolps lunapps L.). Also. spherical shaped seeds
(e.g.. cabbage) are more resistant than elongated or
irregularly shaped seeds. High moisture seeds tend to
bruise whereas dry seeds tend to fracture during mechanical
impact. Drying too slowly or rapidly or at excessively
high temperature (above 38°C for most horticultural
crops) can damage seeds and reduce storability (Base.
1980). Dry seeds are easily damaged during rough handling
(Dorrell and Adams. 1969). Therefore. conditioning
equipment and handling procedures need proper adjustment

for each kind of seed.

19

Mechanical injury to corn (2;; 5311 L.) seeds
creates conditions which favor fungal attack ('ortman and
Rimke. 1951). Broken or cracked seed cost of small grains
increases the likelihood of embryo damage by chemical
treatment (Bonvicini. 1951). Both fungal infection and
chemical injury reduce the keeping quality of stored seeds
(Justice and Bees. 1978). Sometimes seed treatment
chemicals directly affect the viability of healthy seeds in
storage. Nakamura et el. (1972) found egg plant (Solpnpm
pelongema L.) seeds treated with four organomercury
compounds at the rate of 8g/kg of seeds almost completely
lost their viability (O-3$) after one year of storage at

25°C and 66$ RH when the initial germination was 89$.

Storage Environment

Three major factors which influence the longevity of
seeds are moisture content. temperature. and 0; pressure
(Owen. 1956. Barton. 1961. James. 1967). However. seed
storability can be increased by decreasing these factors
(Roberts. 1972b). In most species. seeds remain viable for
longer periods when both moisture content and storage
temperature are low. On the contrary. seeds of some
species such as mango (Mpngifera ipdipa L.). coffee (Coffpp
prapipa L.). etc.. deteriorate rapidly at low temperature

and moisture. These seeds are classified as "recalcitrant"

20

seeds. These seeds are stored at moisture levels generally
above 20$ at ambient temperature not lower than 15°C.
except in a few cases which tolerate as low as 4°C (Chin.
1978).

Mpipgpre pontent. Seeds absorb moisture from the
relative humidity of the air. Moisture content of the
seeds. therefore. fluctuates with an increase or decrease
of relative humidity. There is evidence (Barton. 1941.
Harrington. 1960s) that moisture content ($) of seeds in
equilibrium with a specific relative humidity varies with
the crop species and varieties. at a constant temperature.
Difference in moisture content among different kinds of
seeds is due to differential water absorption and retention
rate. Obviously. thickness. seed cost structure and
chemical composition of seeds affect the rate of water
absorption and retention by seeds. Among the various seed
constituents. proteins are most hygroscopic. carbohydrates
are slightly less and lipids are hydrophobic (Base. 1979).
The influence of seed composition on moisture content of
seeds is evident from Harrington's report (1960a).
According to the report. spinach (Spipppip olerppeg L.)
seeds (starchy) contain 13.2$ moisture (wet basis) and
cabbage seeds (oily) contain 9.6$ moisture at 75$ RH and

25°C.

21

Harrington (1972) generalised the problems of

storing high moisture seeds as follows:

 

Seed Moisture (above) Problems
40-60$ Germination occurs.
18-20$ Heating may occur due to high

respiration of seeds and
micro-organisms.

12-l4$ Fungi grow on and in seeds.

8-9$ Insects become active and
reproduce rapidly.

 

In general. the moisture range 4-8$ is safe for storing
vegetable seeds in sealed containers (Harrington. 1960a).
Ihen seeds are dried below 4-5$ moisture content.
deterioration is somewhat faster than with seeds of 5-6$
seed moisture. This is probably due to the breaking of the
protective monomolecular layer of water around the
macromolecules. exposing them more readily to damage from
free radicals. As a result. cell membranes are disrupted
and DNA of the chromosome is inactivated (Harrington. 1972.
1973). Low moisture seeds are susceptible to mechanical
injury which causes them to deteriorate faster in storage
(Moore. 1972). Nutile (1964) reported that effect of
extreme desiccation varied among crop species. Viability
of carrot and tomato seeds was seriously impaired while the

viability of cabbage. cucumber. onion. and lettuce seeds

22

was not seriously affected. however the germination rate
was reduced (indication of vigor loss) after storing in
sealed metal cans at O.4$ moisture for five years at
23-30°C. Justice and Base (1978) summarised the
desiccation injury symptoms of seeds of different species.
including cracked cotyledon. damage to food transport
system in the embryo. stunted redicle with unusually heavy
development of secondary roots. stubby primary root and
shoot. protrusion of redicle without further development
and decreased germination compared with undamaged seeds.
However. the end result of both high and very low moisture
seeds is the same. as in both cases seeds lost their vigor
and viability in storage.

Temperature. In general. storage life of seeds
increases as the temperature decreases within certain
limits. Onion and lettuce seeds germinated 61$ and 9$
after storage at 35$ RH for one year at 5° and 30°C.
respectively (Barton. 1941). Similarly. ryegrass (Lplium
pultiglopum Lam.) seeds with 8$ moisture stored at 38°C
completely lost their viability while the seeds stored at
3°C retained their initial germination after 18 months
storage (Ching et al.. 1959).

The adverse effect of high temperature on seed
longevity in storage can be reduced with decrease of seed
moisture. For example. at 9.4$ moisture content. soybean

seeds (cv. Mammoth yellow) lost viability after 24 months

23

and at 18$ moisture content completely lost their viability
within 3 months when stored at 30°C (Tools and Toole.
1946). The superiority of subfreesing temperature over
high temperature is well documented for storage of many
kinds of seeds including onion (Hanson and Moore. 1959).

On the other hand. viability of some seeds. e.g.. parsley
(Petropelinum crippum Mill.). pansy (Viplp ppipplpp L.).
snapdragon (Antirrhinum ppjpp L.) reduced in storage at
-20°C ('eibull. 1952. 1955).

The degree of freesing injury to seeds is affected
by genotype. moisture content. temperature. and treatment
duration. Vhite (1909) found that the seeds of parsnip
(Paspinape patiyp L.). and parsley were severely injured.
but castorbean (Ricinus ppmmunip L.) and cress (Lepidipm
pgtivum L.) remained unharmed after exposure to -200°C
for 1.5 days. Lettuce seeds were damaged at 19.4$
moisture. but at or below 13.9$ moisture no freesing injury
was observed at -70° and -196°C (Standwood et al..

1978). As regards duration of freesing exposure. Rossman
(1949) indicated that continuous freesing was more
injurious to two hybrids of corn than repeated freesing and
thawing when total times were equal.

nggpn pgepgppe. The third major factor in seed
survival is oxygen pressure. Free radicals are formed due
to the action of light and other radiation on unsaturated

lipids of the membranes in seed cells under dry storage

24

condition. Oxygen combines with these free radicals to
form hydroperoxides. These hydroperoxides eventually lead
to inactivation of ensynes. denaturation of protein. and
disruption of nucleic acids (Roostra and Harrington.
1969). Therefore. the higher the 02 concentration. the
shorter the life span of seeds as reported in many species
such as maise (Struve. 1959). lettuce. onion (Harrison.
1966). barley. broadbeen (1121; Lppp L.). and pea (Pipp;
papivum L.) (Roberts and Abdalla. 1968). However. the
period of viability of seeds in storage can be prolonged by
a decrease in partial pressure of 01 particularly at

lower temperature and moisture (Roberts. 1972b).

The deleterious effect of high concentration of 02
on seeds in storage can be reduced by treatments with
antioxidants. Harrington (1973) reported that the natural
antioxidant. tocopherols. which are produced ensymically
combine with free radicals rendering them harmless.
Raloyereas et al. (1961) successfully extended the storage
life of onion and okra (Apelmosphus pspplpntpp [L.I Moench)
seeds after treatment with starch phosphate or
alpha-tocopherol. Recently. Voodstock et al. (1983)
reported that impregnation for 4 hours with 20 units/ml
vitamin E and 10’1M butylated hydroxytoulene (BHT) in
acetone improved the storability of parsley and onion

seeds.

25

Finally. it can be stated that low moisture.
temperature. and 0; pressure are the ideal conditions for
seed storage of most species. Vhen these conditions are
unfavorable. their effects become additive. but also
interact to accelerate the seed deterioration process in

storage.

0r anisms Asso is h Se ora e

Five major organisms associated with seeds in
storage are: fungi. insects. mites. bacteria. and rodents.
The activity of each of these can lead to loss of vigor or
viability of seeds (Roberts. 1972b).

The storage fungi comprise chiefly species of
Appergillus and Penicillium. Their major effects on stored
seeds include decreased germination. discoloration.
production of mycotoxins. heating. development of mustines.
and ceking (Christensen. 1972). All storage fungi are
inactive below 62$ RH (semenuik. 1954). and grow profusely
above 75$ RH (Bottomley et al.. 1950). and at temperatures
between 20-40°C (Hall. 1970). Storage fungi are not
obligate anaerobes and therefore fungi growth substantially
decreases as oxygen pressure is lowered from 21$ to 0.2$
(Peterson et al.. 1956). Tao ct al. (1974) found the
growth of Appergillus pppp; on pea seeds treated with
fungicide 'pentachloronitro bensene' after 10 weeks storage

at high temperature (30°C) and high relative humidity

26

(90$ RH). However. the most effective method of preserving
seed quality is to store seeds at moisture contents which
do not favor fungal growth (Christensen. 1972).

The insect past of stored seeds are primarily
different kinds of beetles and weevils. The insects are
active at seed moisture 8 to 15$ (Cotton. 1954). grew
rapidly at temperatures between 28-34°C (Barges and
Burell. 1964) and die at 40-42°C (Thomson. 1952).

Mites do not survive below 60$ RH. but multiply
rapidly at above 75$ RH (Oxley. 1948) and remain active at
temperature range 3-31°C (Harrell. 1970). Insects feed
indiscriminately on the whole seed. while mites feed only
on the germ and thus destroy their germination capacity
(Oxley. 1948). Insect control measures include thorough
cleaning and fumigation of all seed handling equipment.
seed containers. storage areas. and application of
insecticides as required (Justice and Base. 1978).

Bacteria are of minor importance in seed storage as
the relative humidity requirement for their growth is above
90$ which seldom occurs in commercial storage (Justice and
Bees. 1978).

Rate and mice destroy thousands of pounds of seeds
every year by eating. scattering. and mixing. They can be
controlled by using traps. poison bait. or fumigation

(Justice and Bass. 1978).

27

Changes 1p Sec p_During Storpge

The storage condition. not the duration. is the
critical factor influencing the physiological. biochemical.
and genetic changes in stored seeds (Roos. 1980).
Unfavorable storage conditions accelerate the rate of
changes. Most of these changes reflect the loss of vigor
and ultimately the viability of seeds.

Physiological changes include (a) induction of
secondary dormancy as in lettuce seeds after storage at 67$
RH and 10°C (loser and Thompson. 1957). (b) loss of
primary dormancy after storage such as fresh cat and
barley. (c) shift in temperature requirement for
germination. e.g.. seeds of redroot pigweed (Amaranthus
rctroflegpp L.) do not germinate at below 40°C. but are
capable of germination at lower temperature after dry
storage (Roos. 1980). (d) production of abnormal seedlings
such as bald head in been (Toole and Toole. 1953a). red
cotyledon in lettuce (Bass. 1970). absence of cotyledonary
knee and undeveloped primary roots in onion (Clark. 1948).
(e) delay germination and slow elongation of roots in
broadbeam. barley. and pea (Abdalla and Roberts. 1969b).
and (f) reduction in yield in some crops such as onion
(Newhall and Hoff. 1960).

Biochemical changes occur in stored seeds in

different forms. The major biochemical changes include

28

(a) increase in reducing sugar and decrease in nomreducimg
sugar (Zeleny. 1959). (b) decrease in protein content and
its solubility and digestibility (Jones et al.. 1942) and
coagulation of protein (Crocker and Groves. 1915).

(c) impairment of protein synthesis systems (Abdul-Baki.
1980). (d) autoxidation of lipids (Roostra and Harrington.
1969. Roos. 1980). (a) increase in activity of ensymes such
as nuclease (Osborne et al.. 1974). and the decrease in
other ensynes such as (x-emylase (Aspinall and Paleg.
1969). (f) reduction of ATP (Ching. 1982). (g) damage to
membranes and cellular organelles (Berjak and Villiers.
1970. Roberts. 1972c). and (h) failure of cellular repair
mechanisms (Villiers. 1972).

The most important genetic change in stored seeds is
the chromosomal aberration. Some chromosome abnormalities
include fragmentation. bridges. fusion. inversion. chain of
chromosomes. and ring chromosomes (Naswashin and
Gerassimowa. 1936a.b). Chromosomal aberrations had been
reported in stored seeds of many crops such as onion and
lettuce (Harrison and Mcleish. 1954). Other genetic
changes such as mutation causing pollen abortion.
chlorophyll deficiency were observed in aged pea.
broadbean. and barley seeds (Abdalla and Roberts. 1969a).
However. danger of genetic damage vie chromosome aberration
is minimal due to elimination of aberration during plant

growth (Roos. 1980).

29

Methodp_of Omipn Seed Sporage

Because of the high value of the onion crop and poor
storability of its seeds. particularly under hot and humid
conditions. various methods had been attempted to maintain
seed vigor and viability in storage.

Onion seeds could be successfully stored by lowering
relative humidity or moisture content (Barton. 1943.
Hopkins et al.. 1947. Rocks. 1959). temperature (Barton.
1953. Veibull. 1956). and in some cases both temperature
and moisture content (Brown. 1939. Beattie and Boswell.
1939. Game. 1948). Other methods of storing onion seeds
include vacuum storage (Brison. 1942). gas storage e.g..
C02 (Lewis. 1953. Harrison and McLeish. 1954. Harrison.
1956). storage in liquid nitrogen (Harrison and Carpenter.
1977. Standwood and Roos. 1979). and hypobaric storage
(Lougheed et al.. 1976). Game (1948) suggested that onion
seeds might be stored with desiccants such as calcium
sulfate (CaSOg) and silica gel. Onion seeds which were
stored at room temperature in a desiccator over calcium
chloride (CaClz) reached a moisture content of 1.2$ and
retained viability without loss for nine years (Anon..
1954). Similarly. Newhall and Hoff (1960) maintained 75$
germination of onion seeds (cv. Brigham fellow Globe) after
22 years storage with an initial germination of 99$ in a
desiccator over CaClz at room temperature. Plants

produced from these seeds were normal. but bulbs were

30

slightly smaller than those obtained from fresh seeds of
the same cultivar. Nakamura (1975) stored onion seeds (cv.
Imaiwase) with initial germination of 83$ at room
temperature sealed with CaClz and calcium oxide (CaO).
After five years storage. onion seed stored with CaClz
contained 7.9$ moisture and retained about 70$ germination
while CaO stored seeds had moisture content 2.5$ and
maintained 81$ germination.

All those reports indicated that only calcium
chloride and calcium oxide were extensively used to dry and
to store onion seeds. Therefore. there is further scope

for using other desiccants for onion seed storage.

Use of Desiccants in Seed Storage of Other §pepiep

Besides onion. seeds of other species retained
viability when dried and stored with different chemical
desiccants. The viability of carrot. lettuce. tomato. and
eggplant dropped slightly after six years when dried and
stored over calcium oxide at room temperature (Barton.
1939). Storage with silica gel improved the keeping
quality of cucumber. beet (Egg; vdlgdrip L.). and cabbage
seeds (Coleman and Peel. 1952).

Nakamura (1975) reported that seeds of pea. garden
been. broadbean. carrot. cucumber. spinach. eggplant.
radish. pepper. and squash (Cucurpipa ppp.) all retained

good viability longer at room temperature when sealed with

31

CaClz than with CaO. The seeds of smooth bromegrass
(Bromus inermis Leyss.). fescuc grass (Broppp ppdplpddpp
H.B.K.) maintained their germination better and longer at
room temperature when stored with CaO than CaClz.
Further. it had been reported that CaClz could help in
maintaining seed viability of several species at high
storage temperature including rice for one year at 40°C
with 10$ moisture (Rondo and Okamura. 1931). bamboo
(Bambusa mpltipdex [Lour.] Raeuseh). for 202 days at above
32°C ('hite. 1947). and gechip indipp for 14 months at
30°C (El-Shishiny. 1953).

Hence. it is clear from the review of these studies
that desiccants can successfully sustain good viability of
seeds in storage by lowering the seed moisture content. but

information about their effects on seed vigor is lacking.

Priging

In principle. the technique of priming involves
permitting enough water uptake by seeds to make them
physiologically active and enable them to undergo the
initial stages of germination. but not enough to permit
redicle emergence (Heydecker. 1975). Various chemicals
such as NaCl. NaNo3. RN03. polyethylene glycol (PEG).
mannitol. sucrose. and glycerol have been used as osmotica.

PEG. which is physiologically inert (Michel and

Kaufmann. 1973) has been used extensively in priming seeds

32

for rapid and uniform germination of many species like
celery (A2125 graveolens L.) and carrot (Heydecker et al..
1974). parsley (Elly. 1976). tomato (Lightburn. 1976).
spinach (Atherton and Farooque. 1983). The rate and
uniformity of germination of onion seeds (cv. Excellent)
increased in response to 23 days osmotic pre-treatment in
PEG solution of -10 bars potential at 10°C. Primed and
surface dried onion seeds required 20 hours for germination
at 10°C compared with 9.3 days for nonprimed seeds
(Heydecker et al.. 1973). Turner (1977) reported that
onion seeds (cv. Hygros) primed with -12.3 bars PEG
solution for 27 days at 10°C and then dried back reached
50$ germination in 2.7 days compared with 5.9 days for
untreated seeds. The total seed germination was 95$ in
both the treatments. Furutani (1982) observed that priming
onion seeds (cv. Cima) with PEG at -11 bars for two days at
10°C and subsequent drying back resulted in 50$
germination in 7.3 days with total germination of 80.6$.
In contrast. nonprimed onion seeds germinated 50$ in 6.9
days. with total germination of 91.9$. All these reports
demonstrate that the effects of priming treatment with
PEG 6000 on onion seeds may differ according to osmotic
potential. priming duration. drying treatment. and variety.
Priming with different osmotic agents other than PEG
increased rate and uniform germination of seeds in many

crops like tomato with 2$ NaCl or R3P04 (1-2$) + RN03

33

(O.5-2$) solution (Ella. 1963). celery seeds with 1$ of
RN03 + R3P04 (Salter and Derby. 1976). wimterwheat
(Tritipum aestivun L.) with -3.5 to -18 bars mannitol
(Thill et al.. 1979). and onion with -11 bars mannitol or
NaCl (Furutani. 1982).

Levitt and Hamm (1943). and Ella (1963) hypothesised
that regulating the moisture level within the seed
increased the rate of germination. This hypothesis was
made evident by measuring more 0; consumption (Ioodstock.
1969) and large accumulation of nucleic acid. especially
ribosome RNA in primed tomato seeds (Coolbear et al..
1980).

The beneficial effects of priming treatment with
various osmotic solutes may disappear due to complete
redrying of primed seeds. high osmotic concentration. and
insufficient 0; supply. Redrying diminished the benefit
from osmotic pretreatment with PEG in terms of both
earliness and uniformity of germination of onion seeds
(Turner. 1977. Heydecker and Gibbins. 1978). and rate and
percent germination of spinach seeds (Atherton and
Farooque. 1983). Delayed germination of redried-primed
seeds is probably due to degradation of ribosomal RNA and
other newly synthesised protein products during redrying
(Heydecker and Gibbins. 1978). Sugar beet seeds primed in
high concentration of 0.4 to 1.0 molar NaCl solution

exhibited severely stunted redicle growth'and seedling

34

development (Durrant et al.. 1974). High viscosity of

PEG 6000 depresses the 02 availability to the priming
seeds (Mexal et al.. 1975). But the salts have the
advantage over PEG that they do not reduce availability of

02 within the solution (Heydecker and Coolbear. 1977).

MATERIALS AND METHODS

Onion (cv. Early Tallow Globe) seeds in hermetically
sealed cans were obtained from Asgrow Seed Co.. Ralamasoo.
Michigan. These seeds contained 7$ moisture (wet basis) as
determined by the drying oven method at 105°C for 16
hours (ISTA. 1966). Initial seed germination was recorded
as 92$. Desiccants (4-8 mesh) such as Ca804. CaClz.
activated alumina and silica gel were used for drying and
storing high moisture onion seeds.

Moistur Content $ of Onion See in E ui r m
with Different Relat ve Humi itie RH 'C

This experiment was set up to determine the moisture
content of onion seeds in equilibrium with air of high
relative humidity and high temperature which are the
conditions typical of tropical environments. The second
objective of this experiment was to ascertain the relative
humidity in which onion seeds absorb 5-7$ moisture. This
moisture range is considered safe for storage of oil and
vegetable seeds (Harrington and Douglas. 1970). Different
relative humidities were achieved with aqueous solutions of
H2804 at concentrations of 20. 30. 40. 50. and 60$

inside the glass jars (500 m1) closed with gasketed lids.

35

36

Relative humidity ($) in equilibrium with aqueous solution
of each H2804 concentration at 30°C was calculated by
the following formula (Hall. 1957):

P
P

o
where:
P - partial vapor pressure of aqueous solution of H3804
po - vapor pressure of pure water
The basic data for vapor pressure of water and the partial
vapor pressure of aqueous solution of H2804 at 30°C
(Lilcy and Gambill. 1973) were used in calculating the
relative humidities (Table 1).
Table 1. Moisture content ($ wet basis) of onion seeds in
equilibrium with different relative humidities of

aqueous solutions of different H2804
concentrations at 30°C

 

H2804 Percent
($ Acid by It.)

 

Relative Humidity Moisture Contentz

 

20 87 14.0
30 75 12.2
40' 57 9.1
50 36 6.9
60 17 4.2

 

zMean value of three replications.

Onion seeds (5g) were kept in cheesecloth suspended over
200 ml of the different dilutions of H2804 in the jars

which were covered with gasketed lids. Each treatment was

37

replicated three times. All the jars were arranged in a
completely randomised design inside the incubator at
30°C. Moisture content of seed from each jar was
determined at a 3 day interval by the oven method. Ihen
the moisture of the seeds remained fairly constant. that
moisture was recorded as an equilibrium moisture content

(Table 1) with the relative humidity inside the jar.

Effect of Different Te ratures a

Relative Humidity op Vigor and Zippilipy pf Onion Seeds

This experiment was designed to determine the effect

 

of four different temperatures (10°. 20°. 30°. and
40°C) at 75$ RH on the vigor and viability of seeds
during a 12 week storage period. Each temperature
treatment required three glass bottles (2000 ml)
representing the three replications. A cheesecloth bundle
of 15g onion seeds (7$ initial m.c.) was kept hanging
inside each glass bottle containing 500 ml of saturated
NaCl solution to maintain 75$ RH (Hall. 1957). All the
glass bottles for each temperature treatment were arranged
in completely randomised design in rooms that provided
10° and 20°C temperature and in incubators that
maintained 30° and 40°C.

At one-week intervals during 12 weeks storage
period. 25 seeds from each replication of each temperature
treatment were placed for germination in petri dishes

containing double discs of Vhatman No. 2 filter paper and

38

5 ml of distilled water. These petri dishes were covered
and placed in 20°C room. The seeds were checked daily
for germination (visual redicle protrusion). Germination
count was terminated when the number of germinated seeds
remained constant for three consecutive days. Days to 50$
germination (T50) was calculated by the following formula
(Orchard. 1977):
D - fo/Xf

where D - days to 50$ germination

f - number of seeds germinated on day x

x - days after sowing

T50 as an index of seed vigor and percent
germination as an index of seed viability were determined
for every temperature treatment at each week interval

throughout 12 weeks storage period.

Determination of Desiccant Dose

The proper quantity of desiccant depends on the
initial moisture content of the seed. amount of seed. and
the level dryness desired to store the seeds (Harrington
and Douglas. 1970). At 36$ RH onion seeds had an
equilibrium moisture content about 7$ (Table 1). Since a
moisture range of 6-7$ (Beattie and Boswell. 1939. Bass et
al.. 1961) is needed for safe onion seeds storage. this 36$
RH was used to calculate the amount of Ca804. CaClz.

activated alumina and silica gel needed to dry high

39

moisture seeds (14.5$ w.b.) to 7$ moisture. Seeds with
high moisture content (14.5$) typical of tropical climate
were obtained by suspending 7$ moisture seeds over water in
nylon cloth inside closed glass jars for 4 days at 10°C
room. For 100g of onion seeds of 14.5$ moisture to be safe
for storage. 7.5g of water must be removed to reduce it to
7$ moisture. i.e.. (100g x 14.5$ - 100g x 7$ - 7.5g

H20). Before the determination of moisture absorption
capacity. each desiccant was dried in an oven at 120°C

for 16 hours and then kept into the desiccator over
aluminum foil until cool. Then. two grams of each
desiccant in cheesecloth were suspended over 200 m1 of 50$
H2804 solution maintaining 36$ RH in a glass jar (500

ml). Three such glass jars representing three replications
were used. Each desiccant with its moisture content from
every replication was weighed at one-day intervals until
the weight remained constant. Moisture content of the
desiccant was determined by subtracting the initial weight
from the final weight at 36$ RH and expressed in percentage
of its total weight (Table 2). Quantity of desiccant
required to dry the 14.5$ moisture onion seeds to 7$ m.c.
was calculated using the following formula (Harrington and

Douglas. 1970):

Moi tur o e ab d
Moisture (g) absorbed per gram
of desiccant

Desiccant quantity 8

40

Table 2. Moisture absorption ($ of total weight of
desiccant) at 36$ RH and doses (g) of different
desiccants

 

 

Desiccant $ Moisture Dose/10g seed
Ca804 6.1 12.92
CaC12 15.0 5.3
Activated alumina 8.4 9.4
Silica gel 16.5 4.8

 

2This amount of desiccant was marked as x dose. while
double of this amount was 2x dose.

In order to allow for any moisture vapor leakage and other
extraneous moisture vapor. the amount of desiccants was
increased by 5$ over the calculated dose. This adjusted
dose of each desiccant (Table 2) was used to dry and store

10g of 14.5$ onion seeds in an airtight plastic bottle.

Effec on Desic an on Dr in orin

of High Moippugp Opion Sppdp

This experiment was conducted primarily to study the
effect of different desiccants on vigor and viability of
high moisture onion seeds stored at hot and humid
conditions. Ten treatments of the experiment consist of
two controls (dry and moist) and four desiccants (Ca804

CaClz. activated alumina and silica gel) each with two

41

doses (x and 2s). The experiment with 10 treatments was
laid out in completely randomised design. Each treatment
was replicated four times.

Hot and humid conditions typical of tropical
environments were simulated inside the incubator. High
temperature (30°t1°C) and relative humidity (75t5$RH)
were maintained inside the incubator throughout the period
of the experiment. High humidity inside the incubator was
maintained by placing trays with water at the base as well
as in each shelf of the incubator. Air was constantly
circulated inside the incubator through a small fan. At
three day intervals. the water content in each tray was
adjusted with additional water. Relative humidity inside
the incubator was weekly measured by an electric RH
indicator from Bacharaeh Instrument Co.. Pittsburgh.
Pennsylvania. U.S.A. This RH indicator measured relative
humidity with accuracy of r5$. Temperature in the
incubator was checked weekly by a thermometer. Ten grams
onion seeds (14.5$ m.c.) were mixed with the required
amount of desiccant and stored in plastic bottles (120 ml)
closed with screw caps. Similarly. 10g of dry seeds (7$
m.c.) and 10g of high moisture seeds (14.5$ m.c.) were
sealed in separate bottles as dry and moist control

treatments. respectively. All the plastic bottles

42

containing seeds treated with and without desiccants were
placed inside the incubator for a total storage period of 7
months at 30°t1°C and 75r5$ RH. These bottles were
randomised within the four shelves of the incubator using a
random table.

After each month (30 days) of storage. 40 bottles
(4 bottles/treatment) were removed from the incubator
throughout the 7 month storage period. Desiccants mixed
with seeds were separated and moisture content ($ w.b.) of
stored seeds from each treatment was determined by the oven
method. The remaining seeds were tested for vigor and
viability using the following tests: (a) seedling
emergence at stress (10°C) and optimum (20°C)
temperatures. (b) rate of seedling emergence (T50) at
10° and 20°C. (c) seedling growth rate. (4) electrical

conductivity using Automatic Seed Analyser (ASA) model 610.

Spedling Emergence Test

This test was performed as a parameter to determine
vigor and_viability of seeds both under normal (20°C) and
temperature (10°C) stress conditions. After every month
100 onion seeds from each treatment were sown in each
plastic flat (16 x 26 x 6 cm) containing commercial potting
soil There were four rows of seeds (25 seeds/row) in each
flat. Every other day. water (200ml) was supplied to each

row. Seedlings were counted daily until the number

43

remained constant for three consecutive days. Seedlings
emerged from each treatment at both temperatures were

expressed as percent emergence.

Rate of Seedling Emergenpe Tppp

Seedling emergence rate as an indication of vigor
potentiality was expressed as days to 50$ emergence (T50)
under both at stress (10°C) and optimum (20°C)
conditions. T50 was calculated by the formula as

presented previously.

Electrical Conductiyipy Test

This test was conducted to evaluate the vigor and
viability of seeds after 7 months storage. measuring the
electrical current of seed leachetes by an ASA 610
manufactured by Agro Sciences. Inc.. Ann Arbor. Michigan.
This instrument measures the current flow of leachete from
individual seed in a sample of 100 seeds simultaneously.

The soaking tray which contained 100 cells was
cleaned thoroughly with Chlorox and rinsed with distilled
water three times prior to use. The tray was filled by
dipping in distilled deionised water and uniform level of
water in each cell was maintained by setting an immersion
plate over the soaking tray. One hundred seeds from each
replication of the treatment were put into 100 cells of the
tray. All the trays with seeds and water were kept at

25°C room for 48 hours. After completion of seeking

44

time. a multihead designed with 100 pairs of electrodes was
submerged in the soaking tray to measure current flow in
each cell. The instrument was set at scale select position
3 (1 volt). The amount of current flow (9A) for each seed
was printed in an inserted paper roll. Average current
flow (uA/seed/treatment) was calculated from the total
current flow per treatment divided by 400 seeds (100
seeds/replication). High current flow (uA/seed) indicates

low seed vigor or loss of seed viability.

Seedlings Growth Rate Test

Ihen the number of seedlings remained constant for
three consecutive days. plastic flats with seedlings were
transferred from 20°C room to greenhouse. These
seedlings were allowed to grow there for two weeks. Later
all the seedlings from each treatment were cut at the base
and then dried in an oven at 50°C for 48 hours. Seedling
dry weight (mg/seedling) from each desiccant treatment was
reported in percentage (Table 4) over the dry control

treatment.

Spedlings Apnormalitp

In addition to the tests mentioned earlier.
seedlings from seeds stored seven months under hot and
humid conditions were evaluated for abnormality during
emergence and growth. Abnormality of seedlings was

considered as an index of poor seed vigor. Seedlings were

45

classified abnormal when they had absent or defective knee
formation. no root or shoot formation. dwarf primary root.
deformed shoot. lack of chlorophyll or any other observable
deformity. Number of abnormal seedlings was reported in

terms of percentage (Table 6).

Onion Seed Storage for 11 Memphp

Sometimes onion seeds need to be kept in storage in
tropical environment beyond 7 months for delay planting or
some other reasons. Therefore. half of the seeds along
with required quantity of desiccants saved from each
treatment at the end of 7 months storage was stored for an
additional 7 months at the same storage environment
(30°r1°C and 75r5$ RH) in airtight plastic bottles.

After 14 months of storage. moisture content of seeds was
determined by the dry oven method (105°C for 16 hours).
T50 and percentage of seedling emergence (20°C) were

recorded as per procedures mentioned earlier.

Primin o Oni m as
dpcelprated agpd peeds.

It was hypothesised that a priming treatment might
increase the rate (reduction of T50 value) and total
germination ($) of aged onion seeds indicating the
improvement of vigor and viability. The effects of priming

treatment on rate and percent germination of onion seeds

46

were evaluated weekly after accelerated aging for 5 to 12
weeks at 75$ RH and 30°C conditions. In all. 24 glass

jars (500 ml) were required to set up the experiment with 3
replications. Two grams of onion seeds in a nylon bag were
suspended inside each glass jar over 200 ml of saturated
NaCl colution. Each glass jar was covered with a gasketed
lid. These 24 jars were stored in the incubator in
completely randomised design. NaCl (saturated aqueous
solution) provided 75$ RH inside the jar while temperature
(30°C) was maintained by the incubator.

After 5 weeks aging. onion seeds were brought out
from each glass jar. One gram of seeds was kept as control
while another gram of seeds was used for priming treatment
with mannitol solution in the osmotic potential of -11 bars
of 0.47 molar concentration at 10°C for 8 days. This
specification of mannitol solution was taken from Furutani
(1982) on the basis of its effect on the improvement of
rate and percent germination of primed onion seeds.

The osmotic potential of a mannitol solution of 0.47
molar concentration at 10°C was obtained by calculation

with Van't Hoff's equation (Salisbury and Ross. 1978):

47

in s-miRT
where
W“ - osmotic potential

m - molality of the solution (moles of
solute/IOOOg H20)

i s a constant that accounts for ionisation of the
solute. For nonionised molecules such as
sucrose or mannitol i may be equal or close to
one

R - gas constant (0.0831 liter bars/mol degree)

T - absolute temperature in degree Relvin

One gram onion seeds (aged 5 weeks) in a nylon bag
was put in each glass column containing 200 ml aerated
mannitol solution (-11 bars) in controlled temperature room
at 10°C. Seeds from each replication were primed in a
separate glass column. The mannitol solution in the glass
column was replaced every 24 hours with a freshly prepared
solution to maintain constant concentration. After priming
for 8 days. seeds were removed from the glass column and
rinsed 3 times with distilled water. The seeds were then
dried at room temperature under continuous air movement by
a small fan for 24 hours. Both primed and nonprimed seeds
(25 seeds/row) were sown in plastic flats containing
'Sunshine Mix.’ There were 3 rows of seeds in each flat
representing 3 replications of each treatment. Mater
(100 ml/row) was applied every other day. The flats with

seeds were placed in a controlled temperature room at

20°C. Daily seedling emergence was recorded for both

48

primed and control treatments. Seedling emergence was
expressed as percent and T50 (days to 50$ emergence) as
calculated by the formula suggested by Orchard (1977). The
same procedures were followed to prime and evaluate onion
seeds at one-week intervals throughout 12 weeks aging

period.

Sppred Seed;

The main objective of this experiment was to improve
the seedling emergence (10° and 20°C) of stored seeds
after priming with mannitol solution (~11 bars). Two grams
seeds were removed from each plastic bottle of all
desiccants and dry control treatments after storage for
seven months at hot (30° t 1°C) and humid (75 t 5$ RH)
conditions. One gram of seeds from each treatment was kept
as the control and another gram of seeds was primed with
mannitol solution by the same manner as the accelerated
aged seeds. After 8 days of priming. seeds were washed
with distilled water (3 times) and dried for 24 hours at
room temperature with a small fan. Later. both primed and
nonprimed seeds were evaluated for their emergence in terms
of percent and T50 at 10° and 20°C as per procedures

mentioned earlier.

49

Statisticdl Analysis

Data from the storage and priming experiments were
statistically analysed by standard procedures for
completely randomised design and split plot design.
respectively. Means were separated by the LSD test.
Correlation and regression analyses were performed using

conventional methods.

RESULTS AND DISCUSSION

E e t 0 Hi h H mi i a e e at
on Onion Spedg in Sporggp

Time to 50$ redicle emergence (T50)-and percent
emergence of onion seeds did not differ significantly
throughout 12 weeks storage at 10° or 20°C at 75$ RH
(Figures 1 and 2). Seeds stored at 30°C and 75$ RH which
are the conditions typical of tropical environment
gradually increased their T50 values (Figure 1) and
decreased the percent emergence (Figure 2) throughout 12
weeks storage. Storage at 40°C and 75$ RH caused onion
seeds to completely lose their viability within 4 weeks
(Figure 2). These results demonstrated how fast onion
seeds deteriorate under hot and humid storage environment.
It is likely that high humidity (75$ RH) and high
temperatures (30° and 40°C) accelerated the aging
process and thus reduced the vigor and viability of onion
seeds stored under these conditions. According to Roberts
and Ellis (1982) during aging of seeds. damage occurs to
all important classes of functional macromolecules--nucleic
acids. ensynes. and membrane components. Damage

accumulates with time at a rate dependent on temperature

50

l

L

l

6

l

4

R

RHTE OF EMERGENCE (T50)

2

l

51

010 DEG C
A20 DEG C
[530 DEC C
*40 DEG C

 

 

 

 

'Figure 1.

v T 1 I ' 1 1 n ' T ' 1

4 6 8 10 12
STORHGE DURHTION (WEEKS)

Days to 50$ redicle emergence (T50) of onion
seeds stored at 10°. 20°. 30°. and 40°C.
and at 75$ RH for 12 weeks.

52

 

 

 

8-
8d
2
Z
is.)
L.)
CED-
(.st
L
U 4
L.)
ES“ 010 DEG c
{5 ‘ A 20 DEC c
1: [g 30 DEG C
is.)
8‘ x 40 DEG c
DO t 21 I 1 I f I 1 lIJ ‘ 1%

4 6 O
STORRGE DURRTION (HEEKS')

Figure 2. Radicle emergence ($) of onion seeds stored at
10°. 20°. 30°. and 40°C. and 75$ RH for
12 weeks.

53

and moisture content. The hot and humid storage
conditions. coupled with high respiration of seeds. favored
the growth of storage fungi which were evident from the
identification of Rhisopds. Appergilldp. and Penipidlipm
ppp. from seeds stored for 12 weeks at 30° and 40°C.

and 75$ RH. This is consistent with observation by Justice
and Haas (1978) who reported that storage fungi invade and
destroy seeds at 4-45°C and 65-100$ RH. Thus. fungal
invasion contributed further to the loss of vigor and

viability of onion seeds stored at high temperature and

humidity.
Effect of Desiccants on Storage
Of High Moistpre Oniod Seeds
Seed Drying

Moisture data of the first month of storage indicate
that both CaClz and Ca804 are faster drying agents than
silica gel and activated alumina. However. moisture
content of seeds remained more or less constant throughout
seven months storage period from the second month.
irrespective of dose and kind of desiccant treatments
(Figure 3). At the end of seven months storage. high
moisture seeds (14.5$ w.b.) were dried to 4.1$ (w.b.) with
CaClz 2x and Ca804 2x. followed by alumina 2x (5.9$)
and silica gel (6.1$). Similarly. at x dose of CaClz.

Ca804. silica gel and activated alumina. the seeds

Figure 3.

54

Moisture content ($ wet basis) of onion seeds at
each month during 7 months storage of high
moisture (14.5$) seeds. Treatment means in each
month are different by LSD test at 1$ level.
LSD.01 values are 0.7. 0.6. 0.5. 0.4. 0.5.

0.5. and 0.4 for 1st. 2nd. 3rd. 4th. 5th. 6th.
and 7th month storage. respectively. Moisture
value is the average of 4 replications.

 

 

55

3pm
.'

CMLCIUB SULFATE CRLCIU" CHLORIDE

if.”

    

 

 

.. cam camel .-
2: 2.“
3. 3.
.- 2
2 an
2:. 2:.
5
s a?
8 3
'3 :3;
ze‘ RO‘

m

 

 

A

m

 

 

 

 

I"
8
'8
a
E

v v

as sin ea s.

s
'8
fl
a
M
S
'8
'8

i.ec T.” s'.ec 0'.
ROM 1 '18 ROM "18

ILUHIMH SILICO NI.

lg.“ am

A

 

 

sift-gem ..

 

 

p
.A

has

A

 

 

 

 

s .ae s.ea 12.

4
’N
'8

81

8

a. . i.eo LOC Lee
°' ' '° mums

56

attained the moisture contents of 5.1. 6.1. 7.1 and 7.3$
respectively. These results demonstrate that the effects
of silica gel and activated alumina are similar in drying
seeds and that the same is true for Ca804 and CaClz at

the 2x dose. Moisture content of onion seeds dried with
Ca804 and CaClz of both doses were significantly lower

than the silica gel and activated alumina. Furthermore. it
appeared (Figure 3) that the higher dose (2x) of each
desiccant dried seeds at a faster rate and to a lower
moisture content than the lower dose (x). All the
chemicals proved to be very good desiccants in drying high
moisture onion seeds. however. CaClz deliquesced quickly

as it absorbed moisture when exposed to the humid
environment. Its use as a desiccant. therefore. might
cause problems in tropical countries. The seeds in the dry
control treatment absorbed some moisture (7 to 7.6$) from
outside. Similarly. seeds of moisture moist control
treatment lost some moisture (14.5 to 12.1$) during seven
months storage. indicating that the plastic containers were

not completely moisture-proof.

Seedling Emergence
Days to 50$ emergence (T50) of seedlings at 10°C

(stress temperature) (Figure 4) and at 20°C (optimum
temperature) (Figure 5) increased each month throughout 7

months of storage in all desiccant treatments and dry

57

control. Increased T50 meant slow seedling emergence
that was associated with slow seed germination and redicle
growth. This observed loss of vigor and decreased
germination rate are consistent with the reports by
Heydecker et a1 (1975). The gradual trend of declining
vigor as evidenced by slow seedling emergence during aging
is well documented. Thus. aging is a natural sequence that
leads to gradual loss of vigor and ultimately viability
(Anderson. 1970).

In these studies. it appeared (Figure 4 and 5) that
onion seedlings emerged faster at 20° than 10°C
regardless of treatments throughout 7 months storage. In
explaining the faster seed germination in clover seeds at
20°C. Ching (1975) reported that rate of protein
synthesis. soluble protein content. and anabolic ensynes
(e.g.. fumarase. glutamine synthetase. phosphatase and
a-amylase) were higher at 20° than 10°C. Quicker onion
seedling emergence at 20° that at 10°C may likewise be
explained in the above manner. Insignificant interaction
(desiccant and dose) indicates that Ca804. CaClz.
activated alumina and silica gel responded alike regardless
of their doses. (x. 2x) with respect to days to 50$
seedling emergence (T50) at both 10° and 20°C.
T50 values in all desiccant treatments and dry control
after 7 months storage varied from 16 to 16.6 days at

10° and from 7.7 to 8.4 days at 20°C. Among all these

58

treatments. seeds from the dry control took the maximum
number of days to 50$ seedling emergence at both 10° and
20°C. Higher moisture content (7.6$) of seeds in dry
control compared to seeds stored with different desiccants
in tropical condition might contribute to greater vigor
loss as indicated by higher T50 values. T50 value of

dry control at 10°C was not different from that of each
desiccant treatment except 2x dose of CaClz and alumina.
Similarly. the T50 value of dry control at 20°C varied
significantly only with alumina treatments. The T50
values at 10° and 20°C were positively correlated

(r - 0.73“) (Table 5). This indicates that the trend of
vigor expression in terms of the rate of seedling emergence
(T50) would be similar under both stress and optimum
emergence temperatures.

In the moist control treatment. high moisture onion
seeds (14.5$ w.b.) with 92$ initial germination completely
lost their viability within 4 months of storage in sealed
plastic bottles at 30°tl°C and 75t5$ RH conditions.
Unfavorable storage conditions accelerated the seed aging
and favored the growth of storage fungi. identified as
Rhigopup. Appcrgillus. Penipillium ppp. Rapid loss of
vigor and viability of onion seeds was presumably due to
degradation of membranes caused by aging (Delouche and
Baskin. 1973. Robert and Ellis. 1982) and fungal infection

(Herman and Granett. 1972). Seedling emergence from onion

 

 

 

 

59

.emofiueouuneu

v we emeueee emu sq cede» cnh .eAumol h «o momuen anemone
neuua ov.c I no.nma up uneneuumm one ancel uncluecnh
.emeuoue amunom h menace maeom hucbe nu emcee deuce

menu coca an omen—meea «c Acnhv cememuele ion on aha:

 

.v eumumm

60

 

 

828.: 8:! ~88: 32': 8.8a 8.8..
.e p. .u e. a .u r p. .o p. p. L. p. .11.
also 5 e _.

,1
.8
CI

1 7*
II 9|
(ORA) same

w
.8

 

 

 

 

 

 

 

 

 

.2—‘. 3:: in. .‘=!. ‘3: 3;
PP b. h. h. >0 PO ( DO #0 b. P. b‘ b. as.
. l
.218 5 e .. w...
s! M . es s
i I O . .
also I... . .n v...
v" H vs.-
m
.u Tn
009'
g g r“ E3 as r“

(091 i ”will!

61

.enouueounneu v

we eunuch. emu one enema» aha .aAumem h «o mouuen euaueue
neuua .nv.o a no.9»; he uneneuuam one aneem unemoeeuh
.e-auoue emunom p nuance Jamel hueee ma emcee deuce

menu coca an anew—veea me “away eenemnele tan ea «he:

.n cumuum

62

.2!. .—C! t».
up 0 o o a a

b L > b P

 

coca
as

.ux—Il. 8:: g;

 

(081)

 

—T ‘7‘ W ‘7:
I081) ”D8383

j
8

 

r
.I

.‘i. .—E
o O I o
F

F D r

 

g».
a .-

. Ar

'1.
”m3“:

 

 

 

u
s
w
v.
”.8 fi
ii M
3:8... 8:: 82.2..

e to p. .e .a .a .s
1.8 E . W.
San mm s .

3
sue a a W.»
.580 sum . i. m
u
cl
V.)
n
w
v.
0.8 *-
gig u

 

63

seeds stored with desiccants including dry control ranged
from 80 to 86$ at 10° and 82 to 87$ at 20°C following 7
months storage (Table 3). There was no significant
difference in seedling emergence among desiccant
treatments. This demonstrates that drying and storing high
moisture onion seeds with x and 2x of any desiccant did not
affect seed viability. The positive correlation

(r - 0.75") (Table 5) between 10° and 20°C for

seedling emergence ($) indicated that total number of
seedlings was not affected by the emergence temperature
either 10° or 20°C. The inverse correlation

(r - 0.45“) between seedling emergence ($) and T50 at

20°C (Table 5) provided the evidence that seed viability
declined as vigor decreased.

Germination ($) of onion seeds predicted by
nomograph (Ellis and Roberts. 1981) was compared with
seedling emergence ($) in these studies at 10° and 20°C
(Table 3). The predicted germination ($) was positively
correlated with seedling emergence ($) at 10° (r - 0.42‘)
and 20°C (r -O.50“). This suggests that existing
monographs (Appendix B) may be used to predict germination

of onion seeds.

64

Table 3. Seedling emergence ($) at 10° and 20°C and
predicted germination ($) by monograph of seeds
stored for 7 months at different moisture content
and 30°11°C

 

$ Emergencex

 

 

$ Seed Predicted
Treatmentsz Moisture 10°C 20°C Germination
Ca804 x 6.1 85 84 85
Ca804 2x 4.17 86 86 --
CaClz x 5.1 83 85 88
CaC12 2x 4.1V 86 85 --
Alumina x 7.0 84 84 78
Alumina 2x 5.1 84 85 87
Silica x 7.1 83 84 80
Silica 2x 6.1 86 87 85
Dry Control 7.6 80 82 7O
LSD,01 0.4 NS NS --

 

zIn moist control treatment. high moisture (14.5$)
onion seeds completely lost their viability within 4 months
of storage.

’Germination may not be predicted for seeds with
moisture content outside the range of 5-18$ (Ellis and
Roberts. 1981).

xMean value of 4 replications.

65

Sec ling Growth Rap;

 

Dry weight ($ dry control) as a measure of growth
rate of onion seedlings did not differ significantly among
desiccants throughout 7 months storage (Table 4). There
was a highly negative correlation (Table 5) between
seedling growth rate (dry weight) and rate of seedling
emergence (T50) both at 10° (r - 0.82“) and 20°C
(r - 0.73“). This demonstrates that seedling dry weight
increases when T50 decreases and is an indication of
vigorous seeds. Since seedling growth may be influenced by
factors such as oxygen. water supply. temperature. light
intensity (Ching. 1982) and genetic makeup of the seed
(Burris. 1975). the seedling growth rate test may be used
along with other vigor tests to provide better evaluation

of seedling vigor.

66

Table 4. Effects of desiccants on the dry weight of
seedling from onion seeds stored 7 months in airtight
plastic bottle at 30°t1°C and 7535$ RH

 

Dry weight2 of onion seedlings
($ of dry control)

 

 

 

Desiccants Storage Months

1 2 3 4 5 6 7
Ca804 100 101 105 103 104 102 105
CaClz 100 100 101 105 112 108 107
Alumina 102 101 105 104 108 107 108
Silica gel 100 99 104 100 109 105 103

 

zF value was not significant for any storage
period.

67

Table 5. Correlation coefficient between different
variables of onion seedling emergence at 10°

 

 

end 20°C
Correlation

Variable Coefficient (r)
T50 at 10°C vs $ emergence at 10°C -0.05 NS
T50 at 20°C vs $ emergence at 20°C -0.45‘°
T50 at 10°C vs T50 at 20°C +0.73“
T50 at 10°C vs seedling dry weight -0.82‘°
T50 at 20°C vs seedling dry weight -0.73"

$ emergence at 10°C vs seedling dry weight +0.29 NS
$ emergence at 20°C vs seedling dry weight +0.16 NS
$ emergence at 10°C vs $ emergence at 20°C +0.75“

 

"Significant at 1$ level

NS - Not significant

68

Seedling Abnormality

Abnormalities in onion seedlings following seven
months of seed storage in tropical environment were
observed as dwarfed and thickened primary roots.
underdeveloped or missing adventitious roots. chlorophyll
deficiency in shoot. small and twisted shoot compared to
normal seedlings (Figure 6). The number of abnormal
seedlings in dry control did not differ significantly
between x and 2x desiccant doses. Higher dose (2x) of all
desiccants significantly produced more abnormal seedlings
($) than lower dose (x). both at 10° and 20°C emergence
temperature (Table 6). However. more seedlings were
abnormal at 10° than 20°C. Faster drying of high
moisture onion seeds to lower moisture content by the 2x
dose of each desiccant (Figure 3) may cause injury to
physiologically weak seeds resulting in seedling
abnormalities. Nutile (1964) reported that much of injury
from desiccation was revealed as normal sprouts with stubby
root and shoot in certain vegetable seeds such as celery.
pepper. and tomato. He further reported that upon
rehydration of very low moisture seeds during germination.
some biochemical changes occurred that led to delayed
germination. slender seedlings and stubby growth.
Therefore. more abnormal seedlings at 2x doses of desiccant
may be due to the effect of faster desiccation and lower

seed moisture. Higher seedling abnormality at 10° than

69

 

Figure 6. Normal versus abnormal seedlings emerged from
onion seeds after 7 months storage with
different desiccants and in dry control.

70

Table 6. Influence of desiccant doses on the abnormality
of onion seedlings ($) after 7 months seed
storage at 30°rl°C and 75r5$ RH.

 

Abnormal Seedling ($)

 

Desiccant Dosez

 

10°C 20°C
x 3.0! 2.3
2x 4.3 4.0

 

zF value was significant at 5$ level.

JEach value is the mean of 4 desiccants x 4
replications.

20°C may be due to greater chlorophyll deficiency at low
temperature (8°) than at high (25°C) temperature (Gaul.
1964). Similarly. rate of protein and anabolic ensyme
synthesis was lower at 10° than 20°C (Ching. 1975)

which might slow the repair process in aged seeds resulting
in the production of more abnormal seedlings.

Some of the abnormalities of onion seedlings in our
studies were similar to those observed by Clark (1948). He
reported that aging induced abnormal seedlings in onion.
Some of the abnormal seedlings failed to form sharply bent
knees. and many had blunt. undeveloped. or dwarfed primary
roots. According to Clark. cotyledonary cells failed to
enlarge causing no knee formation and failure of root cells

elongation produced dwarf primary roots.

71

Chlorophyll deficiency in seedlings resulting from
aged seeds was reported previously in crops such as barley
(Abdalla and Roberts. 1969a. Murata. 1979). broadbean and
peas (Abdalla and Roberts. 1969a). Chlorophyll deficiency
in these crops was caused by recessive gene mutation. For
the demonstration of recessive genes mutation. it is
necessary to continue observations to the second generation
(Villiers and Edgcumbe. 1975). But in our studies. whether
chlorophyll deficiency was due to recessive genes could not
be determined since observations were not continued to the
second generation. It was observed that some abnormal
seedlings recovered from abnormalities and grew normally
when they were transferred from controlled room temperature
(20°C) to the greenhouse. This recovery of abnormal
seedlings may be due to warmer temperature and higher light
intensities. Similarly. it had been reported (Ching and
Schoolcraft. 1968) that abnormal seedlings. (stubby. wilted
redicle) of crimson clover recovered and chlorophyll
deficiency disappeared under warmer temperature and higher
light intensity (Helm. 1965). Increased ensynes synthesis
(Ching. 1958) and repair of damage (Ching and Schoolcraft.
1968) under favorable growing conditions probably

contributed to the recovery of abnormal seedlings.

72

Seed Ledchates
The Automatic Seed Analyser - 610 (ASA-610)

quantified the leachetes of individual seeds by measuring
the current flow (“A/seed) of leachete from onion seeds
stored with and without desiccants for 7 months in airtight
plastic bottles at 30°t1°C and 7535$ RH conditions.
Higher current values (uA/seed) were recorded at the 2x
than x dose of each desiccant. This indicates greater
exudation from seeds stored with higher dose of
desiccants. Difference in current values (uA/seed) between
x and 2x doses of each desiccant is possibly due to
variation in moisture content. Lower seed moisture content
at 2x doses was apparently responsible for higher current
value.

Regarding the influence of lower moisture content on
the level of seed exudation. McDonald and Iilson (1979)
reported that average current value (uA/seed) for soybean
seeds decreased as seed moisture increased. Highest
current value (63.3 nA/seed) in soybean seeds occurred with
lowest moisture content (6.5$) and conversely. lowest
current value (46.2 uA/seed) was recorded in soybean seeds
with 18.3$ moisture. Highest electrical current flow of
low moisture seeds indicated the highest conductance of
exudate solution of the seeds. Loss of electrolytes such
as sugars. amino acids. organic acids. and inorganic salts

was possibly greater from low moisture seeds due to damage

73

of cell membranes or disorganisation of their structures.
Thus. greater amount of electrolytes increased the
conductivity in soak water of the seeds. Three hypotheses
had been made by different researchers to explain the
causes of membrane degradation in low moisture seeds:

1. Rapid inrush of water during imbibitiom of dry
seeds which ruptures or disrupts the membrane
structure causing leakage from seeds (Larson.
1968).

2. Free radicals produced during lipid autoxidation
which destroy the cell membranes causing more
leakage of solute from low moisture (4-5$) seeds
(Roostra and Harrington. 1969).

3. Membranes of dry seeds are disorganised and
leakage of solute occurs during imbibitiom due
to delay in their reorganisation (Simon and
Rajaharun. 1972.)

Electrical conductance (proportional to measured
current flow) in exudate solutions of seeds of dry control.
x and 2x doses of all the desiccants except Ca804 did not
differ significantly. Lowest value (33.7 uA/seed) was
recorded for the x dose of Ca804. while the highest (53.7
uA/seed) was obtained in the moist control treatment. Both
values differed significantly from those of other
treatments (Figure 7). Highest and lowest values can be

related to low and high membrane integrity respectively.

74

In the moist control. the seeds were dead. as evidenced
from emergence tests. Similarly. more leaching was
reported from dead seeds of crimson clover and rye (Ching
and Schoolcraft. 1968). Seeds possibly died due to
membrane degradation caused by unfavorable storage
conditions (high moisture seeds. 30°tl°C and 75r5$ RH)

and attack of fungi identified as dhigoppp. Aspergillpp
and Pendcillium Spp. The role of fungi in membrane
degradation had been reported by Herman and Granett
(1972). Pea seeds inoculated with Appergillps £313; and
stored over 92$ RH at 30°C for 14 weeks leaked more
solutes than uninfected seeds. Plasmalemma damage became
extensive with fungal infection and to a lesser degree with
aging as revealed from greater solute leakage and electron
microscope studies. Therefore. it is hypothesised that the
conditions which disrupt membranes are important in seed
leakage. Low vigor seeds possess poor membranes structure
and many leaky cells and thus leach more (Tao. 1978).
Hence. high conductance will indicate poor quality seeds.
According to this. onion seeds stored with 2x dose of
desiccants would be poorer quality seeds than the seeds
with x dose. But this is not true as evidenced from other
vigor tests such as T50 at 10° and 20°C and seedling
growth rate test. There was no correlation between
conductance and T50 emergence or percent emergence at

10° and 20°C. This further confirms that the absence

75

.a.m I «c.naa up unenounum eun.eneel unemueeuh
.ueelueeuu\ameoa ocv no deal emu one earner noun «nonunu
.aaneeemeem unomuue one made emeueua emu-om p «can. ameea
memno we oneneeeu Annoumu Ameoa\<nv noun aneunno neeunueeum

do 3...; 23.5.... «.55 comcu .5528
an a an a a. a a. u see .o..c

,_ AV ,_ _.\ ,_

1 ‘ ‘fifiw
93 03

V V w

,7
k
SE ()8

\
I , \ ,

*‘1
09
UBBS/SdHUOHDIH

Vi ‘
St

inj‘v vi 1 w

99

 

'Yj‘v

.h eummum

76

of a difference between x and 2x desiccant doses in respect
to vigor and viability. Hence. vigor evaluation of onion
seeds by the ASA-610 alone may be misleading. Therefore.
electrical conductivity test by the ASA-610 should be used

only in conjunction with other vigor tests.

Seeds Spored for 11 Months

Seed moisture content. T50 and percentage of
seedlings emergence (20°C) ranged from 4.4 to 8.1$. 7.9
to 9.3 days. and 74 to 86$ respectively among all the
treatments after 14 months storage of seeds at 30°t1°C
and 75r5$ RH (Table 7). Highest T50 (9.3 days) and
lowest seedling emergence (74$) were recorded in dry
control treatment. followed by alumina x and silica gel x.
T50 values of these treatments varied significantly than
the other treatments. Higher moisture content of the seeds
in these treatments possibly caused substantial loss of
vigor (increased T50) and viability (decreased seedling
emergence). However. vigor and viability remained
virtually unaffected in seeds stored with two doses (x. 2x)
of Ca804 and CaClz. 2x dose of alumina and silica gel.
These results suggest that higher dose of desiccants.
particularly of silica gel and activated alumina. will be
better for long term storage of onion seeds in a tropical

environment.

Table 7. Moisture content. T50

77

and percentage of

seedling emergence (20°C) of onion seeds after
14 months storage at 30°r1°C and 7525$ RH in

airtight plastic bottles.

 

 

Moisture Content T50 Emergence
Treatments ($ w.b.) (Days) ($)
Ca804 x 6.3 8.1 81
Ca804 2x 4.5 8.3 86
CaClz x 5.2 8.5 85
CaClz 2x 4.4 8.0 86
Alumina x 7.8 9.2 75
Alumina 2x 6.1 7.9 85
Silica x 7.5 8.8 78
Silica 2x 6.4 7.9 86
Dry Control 8.1 9.3 74
LSD,01 0.3 0.4 9

 

78

Effect of Prigdpg

Accelerated Aged Seedp

Reduction of T50 value (Table 8) as an indication
of vigor improvement was not significant after priming of
onion seeds (~11 bars mannitol at 10°C for 8 days) aged
for 5 and 6 weeks at 75$ RH and 30°C conditions. This
was possibly due to the high vigor potentiality of the
seeds before priming. Since the high vigor seeds have the
ability to repair. reorganise and reactivate the preformed
systems. e.g.. membranes. ensynes. proteins. nucleic acids.
and organelles (Ching. 1982). it is likely that priming
treatment did not have enough opportunity to reactivate the
preformed systems and repair damage of high vigor onion
seeds. During the period of aging seeds for 7 and 8 weeks.
some damages either to cell membranes or organelles might
have occurred in seeds. These seeds possibly had medium
vigor due to loss of vigor to some extent during aging.
After priming. the medium vigor seeds germinated
significantly faster (reduction of T50) than nonprimed
seeds (Table 8). This increased rate of germination was
presumably due to repair of damage of cellular organelles
and membranes during priming. This indicates that priming
could recover the cellular damage and revert the vigor of

seeds. Earlier. Villiers (1973) had shown that in imbibed

79

Table 8. Effect of priming on rate (T50) and percent
germination of onion seeds aged for 12 weeks at
75$ RH and 30°C

 

 

 

Aging Period T50 (Days) $ Germination
Veeks Nonprimed Primed Nonprimed Primed
5 3.7 3.5 92 95
6 4.0 3.8 91 93
7 4.2 3.12 so as
s 4.4 3.91 58 672
9 4.4 4.1 44 49
10 4.9 4.6 36 39
11 5.0 4.7 20 22
12 5.9 5.8 13 13

 

zMeans in the same row are significantly different
at 5$ level by LSD test.

80

lettuce seeds. physiological repair mechanism could operate
more effectively and enable aging seeds to retain or even
restore their germinability.

After aging for 9. 10. 11 and 12 weeks. seeds did
not respond to priming. These seeds possibly had low vigor
potential due to substantial loss of vigor by accelerating
aging conditions. In these seeds. damage was too extensive
to be recovered by priming. Similarly. Berjak and Villiers
(1970. 1972) had shown in maise that damage became
irreversible when aging was much advanced. The results of
our study suggest that vigor is an important component of
priming and that the initial vigor level of the seed can
influence the response to priming.

Priming significantly improved the viability (58 to
67$ germination) of 8 weeks aged seeds. possibly due to
vigor improvement as evidenced from the decreased T50
(4.4 to 3.9 days). However. this may not be always true.
Seeds aged for 7 weeks and then primed improved their vigor
significantly without the improvement of germination (Table
8). In a similar study. Heydecker et a1 (1973) found that
seeds of red beet (cv. Boltardy) significantly decreased
the T50 (from 12.1 to 2.4 days) and improved germination
(from 63 to 79$) after priming with ~10 bars PEG 6000 at
15°C for 21 days. The cause of improved vigor of seeds

after priming was considered by Rhan et al (1978) to result

81

from increased RNA. protein and ensyme synthesis or
activation from osmotic treatment of lettuce seeds with 25$
PEG at 15°C for 2 weeks. Furthermore. our data showed

that T50 values increased and percent germination

decreased with the increase of aging time. demonstrating
that vigor and viability of seeds were reduced by aging.

Aging. therefore. is a progressive deteriorative process.

Stoped Seeds

Priming onion seeds stored for 7 months had
significantly decreased the time to 50$ seedling emergence
(T50) from 16.4 to 11.3 days (Figure 8) and improved
seedling emergence from 84 to 89$ at 10°C (Table 9).
Since the priming and emergence temperature was the same
(10°C). it is likely that physiological and biochemical
processes of germination which are temperature dependent
continued from priming to seedling emergence at 10°C.
Thus. the continuity of those processes over a longer
period may have contributed to substantial reduction of
T50 and improvement of seedling emergence. 'hen primed
seeds were sown at 20°C. time to 50$ seedling emergence
(T50) was reduced from 8 to 7 days (Figure 8). Total
seedling emergence. however. was not significantly
different (Table 9). Reduction of T50 values both at
10° and 20°C as an indication of vigor improvement was

perhaps due to activation of preformed system. increased

82

 

 

c3—
00
J
u:—
w-d
J
AN“
0):-
>' l
a:
D d
:3
U) .l ,
F-ao /
\‘
J \
*I-I
l
‘9 CONTROL PRIHE ccumm. rams

lO DEG C 20 DEG C

Figure 8. Effect of priming of desiccant stored onion
seeds with mannitol (~11 bars) on T50 values
at 10° and 20°C. The F value for priming
treatment was significant (1$ level) at each
temperature.

83

Table 9. Effect of priming of desiccant stored onion seeds
with mannitol solution (~11 bars) on seedling
emergence ($) at 10°C and 20°C

 

Seedling Emergence ($)

 

 

 

Treatmentsz
10°C 20°C
Control 84 85
Priming 89 87
zF value for the priming was significant at 5$
level at 10° but that was insignificant at 20°C.

rate of protein or ensynes synthesis during priming. Low
leakage of solute from onion seeds after priming might also
contribute to decrease T50 value. It is likely that
priming prevented the rapid inrush of water to rupture
membrane structure and gradually reorganised the
disorganised membrane system of dry (4.1 to 7.6$ m.c.)
stored seeds by slowing the inhibition process. As a
result. primed onion seeds possibly leached less compared
to nonprime seeds. Similarly. Furutani (1982) observed
that leakage from onion seeds was reduced after priming.
There was no significant interaction between priming and
kind or rate of desiccant. It indicated that the effect of
priming was independent. Further. the results of this
study suggest that priming of onion seeds may be very

advantageous to seedlings emergence in cold soil.

SUMMARY AND CONCLUSION

Two doses (x. 2x) of Ca804. CaClz. activated
alumina and silica gel were used to dry high moisture
(14.5$) onion seeds and maintain their vigor and viability
for 7 months (harvesting to next planting) after storing
them in airtight plastic bottles at high temperature
(30°:1°C) and high relative humidity (75t5$ RH) typical
of tropical climate. Lowest moisture content (4.1$) was
recorded with 2x dose of both CaSOg and CaClz while
highest moisture content (7.3$) was recorded with alumina
(x) at the end of 7 months storage. Both Ca804 and
CaClz dried the high moisture seeds to significantly
lower moisture and at faster rate than silica gel and
activated alumina. Onion seeds (92$ initial germination)
in moist control completely lost their viability over a 4
month storage. Storage fungi (Rhigopus. dapprgillpp. and
Ppnipillium ppp.) were identified from these seeds. Seeds
of dry control and all desiccant treatments emerged from 80
to 86$ at 10° and 82 to 87$ at 20°C following 7 months
of storage. Time to 50$ seedling emergence (T50) was
faster (7.7 to 8.4 days) at 20° than 10°C (16 to 16.6
days) regardless of treatments. Growth rate of onion

seedlings did not differ significantly. indicating that

84

85

seedling vigor was similar among all the desiccant
treatments. Seedlings abnormalities included dwarfed and
thickened primary roots. underdeveloped or lack of
adventitious roots. small and twist shoot. and shoots with
chlorophyll deficiency. Highest dose (2x) of each
desiccant resulted in more seedling abnormalities than x
dose at both 10° and 20°C emergence temperature.

Electrical conductance (proportional to current flow) of
leachete from seeds stored for 7 months was measured by the
Automatic Seed Analyser-610. In moist control. seeds were
dead as evident from emergence tests. These dead seeds
leached the most as indicated by highest conductance.

Seeds stored with CaS04 (x) leached the least and thus

had the lowest conductance. Higher current value (pA/seed)
was recorded in seeds stored with 2x dose of each
desiccant.

After 14 months storage of seeds at 30°r1°C and
7515$ RH. highest T50 (9.3 days) and lowest seedling
emergence (74$) were recorded in dry control followed by
alumina (x) and silica gel (x). However. in the case of
other treatments. vigor and viability of stored seeds
remained unaffected.

Time to 50$ germination (T50) did not decrease as
a result of priming (~11 bars mannitol solution for 8 days
at 10°C) of onion seeds aged for 5 and 6 weeks at 30°C

and 75$ RH. Perhaps these seeds had high vigor potential

86

before priming. Similarly. seeds aged 9 through 12 weeks
did not respond to priming in improvement of vigor. These
seeds possibly had low vigor potential before priming. due
to extensive damage of cellular organelles and membranes by
accelerated aging. Seeds aged for 7 and 8 weeks perhaps
had medium vigor before priming. These medium vigor seeds
germinated significantly faster than nonprimed seeds.
presumably due to repairing of damage of cellular
organelles and membranes by priming. Priming of 7 months
stored seeds significantly decreased the time to 50$
seedling emergence (T50) from 16.4 to 11.3 days at 10°
and 8 to 7 days at 20°C. Improvement of seedling
emergence was significant at 10° (84 to 89$) but not at
20°C (85 to 87$) after priming.

Research results indicate that CaS04 and CaClz
as well as activated alumina and silica gel can dry the
high moisture onion seeds to lower moisture content and
maintain high seed quality when stored in airtight
containers in tropical environment during the period from
harvesting to next planting. However. higher dose (2x) of
desiccants. particularly of activated alumina and silica
gel. will be better for long term storage of onion seeds as
evidenced from 14 months storage of seeds. Higher dose of
each desiccant promoted faster drying. CaS04 and CaClz
dried the seeds faster than silica gel and activated

alumina. Since CaClz deliquesced rapidly at high

87

humidity. its use as a desiccant in tropical environment
may be disadvantageous. This storage method is simple and
inexpensive since the desiccants are low~priced and
reusable. This storage method can be used to replace the
need for mechanical drying and cold storage of onion seeds.
Therefore. small farmers of Bangladesh. as well as other
tropical countries which have similar seed storage
problems. could benefit from this low cost system of
storing onion seeds.

Vigor evaluation of onion seeds by ASA 610 may be
misleading because electrical current value may be high due
to low moisture content of seeds rather than low vigor
potential as evidenced by this as well as other studies.
Electrical conductance test by ASA 610 should. therefore.
be used only in conjunction with other vigor tests.

Results of priming treatments on accelerated aged
seeds suggest that priming could recover the cellular
damage and revert the vigor potential of onion seeds.
Furthermore. it indicates that vigor is an important
consideration of priming treatments. since initial seed
vigor can influence the response to priming. Accordingly.
very high or very low vigor seeds may not respond to the
improvement of vigor after priming. Perhaps this is the

area which needs further intensive investigation.

Improvement of rate of emergence and level ($) of emergence
at 10°C after priming of stored onion seeds suggest that
priming will be an advantage for seedling establishment in

cold soil.

APPEND I CE S

89

APPENDIX A

TEMPERATURE AND RELATIVE HUMIDITY DURING

THE PERIOD FROM APRIL TO OCTOBER IN BANGLADESH

90

Table A~1. Temperature and Relative Humidity During the

Period from April to October in Bangladesh2

 

 

 

Average
Months
Relative
Minimum (°C) Maximum (°C) Humidity ($)

April 22.8 34.3 72.3
May 24.5 33.3 80.1
June 25.3 31.8 86.6
July 25.6 31.1 87.9
August 25.7 31.3 89.2
September 26.1 31.6 87.1
October 23.4 31.1 84.7

 

2Statistical Yearbook of Bangladesh. 1979.

91

APPENDIX B

SEED VIABILITY NOMOGRAPH FOR ONION

92

so 1! 200 000

 

 

 

 

f 7
r
>
100000 r
i
o >
’ soooo ,
‘ l
e 6
20000 r
)
L0 0 10000 .
l I
b b
5000 ,
4 b s
l
«p '
1) 200° ’
0 l
y
1A Tm )
b s ;
30 0 05
500 , I 1
. ' 5
‘5 ‘o m 'o
A. 100 :2
is ”
20 0 I led
:8 50 , so
40
’ to
‘f to '9
0 L Q
9 2
a 10 l '5
I0 ‘I’ D
,
r ’ 99
5 : '5
1b L
> ’ ”g
t 2 l
m H
0 1p “W I D”
1 T t
.L i
. o s ;
40 3-
.: l
0 el)
1’ oz
.20 ‘d- D t d e f q It
We. More cement. or Stray mac. ear-st mu, Final "ditty. m... "NW.
.C ’6”? den hrs hat Outed 9s 'Mldtlmryfl

Figure B~1. Seed Viability Nomograph for Onion. (Ellis
and Roberts. 1981).

93

BIBLIOGRAPHY

94

BIBLIOGRAPHY

Abdella. F. H. and E. H. Roberts. 1969a. The effects of
temperature and moisture on the induction of genetic
changes in seeds of barley. broadbean and pea during
storage. Ann. Bot. 33:153—167.

Abdella. F. H. and E. H. Roberts. 1969b. The effect of
seed storage conditions on the growth and yield of
barley. broadbean and pea. Ann. Bot. 33:169-184.

Abdul-Baki. A. A. 1980. Biochemical aspects of seed
vigor. Hort. Sci. 15(6):765~771.

Ahmad. R. U. 1976. Flowers. fruits and vegetables. 3rd
ed. Published by Ramisuadin Ahmad. Farmgate.
Dhaka-15. Bangladesh.

Anderson. J. D. 1970. Physiological and biochemical
differences in deteriorating barley seeds. Crop

Anon. 1954. The preservation of viability and vigor in
vegetable seeds. Asgrow Monograph. New Haven.
Conn.. U.S.A.. No. 2. 32 pp.

Anonymous. 1979. Statistical year book of Bangladesh.
Ministry of Planning. Government of the People's
Republic of Bangladesh.

Aspinall. D. and L. G. Paleg. 1969. The deterioration of
wheat embryo and endosperm function with age. J.
Expt. Bot. 22:925-935.

Atherton. J. G. and A. M. Farooque. 1983. Higher
temperature and germination in spinach II. Effect
of osmotic priming. Scientia Horticulture
19:221-227.

Atkin. J. D. 1958. Relative susceptibility of snapbean
varieties to mechanical injury to seed. Proc. Amer.
Soc. Hort. Sci. 72:370-373.

Barton. L. V. 1939. A further report on the storage of

vegetable seeds. Boyce Thomson Inst. Contrib.
10:205-220.

95

96

Barton. L. V. 1941. Relationship of certain air
temperature and relative humidities to viability of
seeds. Boyce Thomson Institute Contrib. 15:85-102.

Barton. L. v. 1943. Effect of moisture fluctuations on
the viability of seeds in storage. Boyce Thomson
Inst. Contrib. 13:35-45.

Barton. L. V. 1953. Seed storage and viability. Boyce
Thomson Inst. Contrib. 17:87-103.

Barton. L. V. 1961. Seed preservation and longevity.
Leonard Hill. London.

Bass. L. N. 1965. Effect of maturity. drying rate. and
storage conditions on longevity of Rentucky
bluegrass seed. Proc. Assoc. Off. Seed Anal.
55:43-46.

Bass. L. N. 1970. Prevention of physiological necrosis in
lettuce seeds. J. Amer. Soc. Hort. Sci. 95:550-553.

Bass. L. N. 1979. Physiological and other aspects of seed
preservation. Pp. 145-170. In: J. Rubenstein. R.
L. Phillips. C. E. Green. and B. G. Grengenbach
(eds.). The Plant Seed: Development. Preservation
and Germination. Academic Press. New York. U.S.A.

Bass. L. N. 1980. Seed viability during long-term
storage. pp. 117-141. In: Jules Janick (ed.).
Horticultural Reviews. vol. 2. AVI Publishing
Company. Inc.. Vestport. Connecticut.

Bass. L. N.. T. M. Ching and F. L. Vinter. 1961. Packages
that protect seeds. pp. 330-338. In: Alfred
Steffeurud (ed.). Seeds. The Yearbook of
Agriculture. USDA. Vashington. D.C.

Beattie. J. H. and V. R. Boswell. 1939. Longevity of
onion seeds in relation to storage condition. USDA
Cir. 512.

Berjak. P. and T. A. Villiers. 1970. Aging in plant
embryo. I. The establishment of sequence of
development and senescence in root cap during
germination. New Phytology 69:929-938.

Berjak. P. and T. A. Villiers. 1972. Aging in plant
embryos. II. Age induced damage seed and its
repair during early germination. New Phytology
71:135.

97

Bittenbender. H. C. and S. R. Rica. 1977. Germination and
growth of rice seedlings from high and low protein

seeds after exposure to various storage conditions.
J. Seed Technology 2(1):62~72.

Bonvicini. M. 1951. Semente digrano sense lesioni commun.
Cong. Assoc. Franc. Progr. Sci.. P. I.

Bottomley. R. A.. C. M. Christensen. and V. F. Geddes.
1950. Grain storage studies 1x. The influence of
various temperatures. humidity and oxygen
concentration on mold growth and biochemical changes
in stored yellow corn. Cereal Chem. 27:217-296.

Brison. F. R. 1942. The influence of storage conditions
upon germination of onion seed. Proc. Amer. Soc.
Hort. Sci. 40:501-503.

Brown. E. 1939. Preserving the viability of onion seed.
Science 89:292-293.

Burges. H. B. and N. J. Burrel. 1964. Cooling bulk grain
in the British climate to control storage insects
and improve keeping quality. J. Sci. Food Agric.
15:32-50.

Burrel. N. J. 1970. Conditions for safe grain storage.
Tech Note 16. Homegrown Cereal Authority. London.

Burris. J. S. 1975. Seedling vigor and its effect on
field production of corn. Ann. Corn and Sorghum

Chin. H. F. 1978. Production and storage of recalcitrant
seeds in the tropics. Acta Horticulturae 83:17-21.

Ching. T. M. 1958. Some histological and physiological
studies on abnormal crimson clover seedlings. Proc.
Amer. Off. Seed Anal. 48:96-99.

Ching. T. M. 1975. Temperature regulation of germination
in Crimson clover seeds. Plant physiology
56:768-771.

Ching. T. M. 1982. Adenosinc triphosphate and seed
vigor. Pp. 487-506. In: A. A. Rhan (ed.). The
physiology and biochemistry of seed development.
dormancy and germination. Elsevier Biomedical
Press.

98

Ching. T. M.. M. C. Parker. and D. D. Hill. 1959.
Interaction of moisture and temperature on viability
of forage seeds stored in hermetically sealed cans.
Agron. J. 51:680-684.

Ching. T. M. and I. Schoolcraft. 1968. Physiological and
chemical difference in aged seeds. Crop science
8(4):407-409.

Christensen. C. M. 1972. Microflora and seed
deterioration. PP. 59-93. In: E. H. Roberts
(ed.). Viability of seeds. Chapman and Hall. Ltd..
London.

Clark. B. E. 1948. Nature and causes of abnormalities in
onion seed germination. Cornell University Expt.
Station. Circular No. 512.

Coleman. F. B. and A. C. Peel. 1952. Storage of seeds.
Queensland Agr. J. 74:265-276.

Coolbear. P.. D. Grierson. and V. Heydecker. 1980.
Osmotic presowing treatment and nucleic acid
accumulation in tomato. Seed Sci. and Technol.
8:289-303.

Cooley. G. E. 1895. On the reserve cellulose of the seeds
of Liliaceae and of some related orders. Men.
Boston Soc. Nat. Hist. 5:1-29.

Copeland. L. O. 1976. Principles of seed science and
technology. Burgess Publishing Co. U.S.A.

Cotton. R. T. 1954. Insects. pp. 152-220. In: J. A.
Anderson and A. V. Alcock (eds.). Storage of cereal
grains and their products. Amer. Assoc. of Cereal
Chemists. St. Paul. Minn.

Crocker. V. and J. F. Groves. 1915. A method of
prophesising the life duration of seeds. Proc. Nat.

Delouche. J. C. 1980. Environmental effects on seed
development and seed quality. Hort. Sci.
15(6):775-780.

Delouche. J. C. and C. C. Baskin. 1973. Accelerating
aging technique for predicting relative storability
of seeds. Seed Sci. and Technol. 1:427-452.

99

Delouche. J. C.. R. R. Mathews. G. M. Dougherty and A. H.
Boyd. 1973. Storage of seeds in subtropical and
tropical regions. Seed Sci. and Technol. 1:671-700.

Dorrel. D. G. and M. R. Adams. 1969. Effect of some
characteristics on mechanically induced seed coat
damage in navy bean. Agron. J. 61:672-673.

Durrant. M. J.. A. P. Draycott. and P. A. Payne. 1974.
Some effects of sodium chloride on germination and
seedling growth of sugarbeet. Ann. Bot.
38:1045-1051.

Eguchi. T. and H. Yamada. 1958. Studies on the effect of
maturity on longevity in vegetable seeds. Natl.
Inst. Agr. Sci. Bul.. Ser. B. Hort. 7:145-165.

El-Shishiny. E. D. H. 1953. Effect of temperature and
desiccation during storage on germination and
keeping quality of Rochia indipa seeds. J. Expt.
Bot. 4:403-406.

Ellis. R. H. and E. H. Roberts. 1981. The quanitification
of aging and survival in orthodox seeds. Seed Sci.
and Technol. 9:373-409.

Ells. J. E. 1963. The influence of treating tomato seed
with nutrient solutions on emergence rate and
seedling growth. Proc. Amer. Soc. Hort. Sci.
83:684-687.

Elly. P. 1976. Parsley seed germination--a new approach.
Nottingham B. So. (hens). dissertation.

Flood. R. G. and A. Sinclair. 1981. Fatty acid analysis
of aged permeable and impermeable seeds of Trigpddpm
pubgerranedn L. Seed Sci. and Technol 9:475-491.

Furutani. S. C. 1982. Low temperature priming and
pregerminatien of celery and onion seeds. Ph.D.
dissertation. Michigan State University. East
Lansing. U.S.A.

Gane. R. 1948. The effect of temperature. water content
and composition of the atmosphere on the viability
of carrot. onion. and parsnip seeds in storage. J.
Agr. Sci.. England. 38:84-89.

Gaul. H. 1964. Mutation in plant breeding. Radiation
Botany 4:155-232.

100

Grebe. D. F. 1976. Measurement of seed vigor. Journal of
Seed Technology 1(2):18-32.

Green. D. E.. L. E. Cavanah. and E. L. Pinnell. 1966.
Effect of seed moisture content. field weathering.
and combine cylinder speed on soyabean quality.

Crop Sci. 6:7-10.

Hall. C. I. 1957. Drying farm crops. Reynoldsburg. Ohio.

Agricultural Consulting Associates. Inc.

Hall. D. I. 1970. Handling and storage of feed grain in
tropical and subtropical areas. FAO Agri. Dev.
Paper. No. 90.

Hanson. C. H. and R. P. Moore. 1959. Viability of seeds
of eight forage crop plants stored under subfreesing
conditions. Agron. J. 51:629.

Harman. G. E. and A. L. Granett. 1972. Deterioration of
stored pea seeds. change in germination. membrane
permeability and ultrastructure resulting from
infection by Aspergillus ppber and from aging.
Physiological Plant Pathology 2:271-278.

Harrington. J. F. 1960a. Drying. storing and packaging
seed to maintain germination and vigor. Seed Man's
Digest 1: 16. 56-57. 64. 66. 68.

Harrington. J. F. 1960b. Germination of seeds from
carrot. lettuce and pepper plants grown under severe
nutrient deficiencies. Hilgardia 30(7):219-235.

Harrington. J. F. 1972. Seed storage and longevity. pp.
145-155. In: T. T. Roslowski (ed.). Seed Biology.
Vol. 3. Academic Press. New York.

Harrington. J. F. 1973. Problems of seed storage. pp.
252-263. In: I. Heydecker (ed.). Seed ecology.
Pennsylvania State University Press. University
Park.

Harrington. J. F. and J. E. Douglas. 1970. Seed storage
and packaging~-application for India. National
Seeds Corporation Ltd. in cooperation with the
Rockefeller Foundation. New Delhi. India.

Harrison. B. J. 1956. Seed storage. John Innes Hort.
IllSt. Anne [’pe 46:15-16e

101

Harrison. B. J. 1966. Seed deterioration in relation to
storage condition and its influence upon

germination. chromosomal damage and plant
performance. J. Nat. Agric. Bot. 10:644-663.

Harrison. B. J. and R. Carpenter. 1977. Storage of Aldpg
cepa L. seeds at low temperature. Seed Sci. and
Technol. 5:699-702.

Harrison. B. J. and J. McLeish. 1954. Abnormalities of
stored seeds. Nature 17:593-594.

Hayward. H. E. 1938. The structure of economic plant.
Macmillan Co.. New York.

Heydecker. I. 1969. Vigor of seeds~-A Review. Int. Seed.
Test. Ass. 34(2):201-217.

Heydecker. I. 1972. Vigor. pp. 209-252. In: E. H.
Roberts (ed.). Viability of seeds. Chapman and Hall
Ltd.. London.

Heydecker. I. 1975. Seed priming-~the treatment of the
future? The Grower. September Issue.

Heydecker. I. and P. Coolbear. 1977. Seed treatments for
improved performance--survey and attempted
prognosis. Seed Sci. and Technol. 5:353-425.

Heydecker. V. and M. Gibbins. 1978. The priming of
seeds. Acta Hort. 83:213-223.

Heydecker. N.. J. Higgins. and R. Gulliver. 1973.
Bringing seeds to the brink of germination. The
Grower. Dec. Pp. 1134-1135.

Heydecker. V.. J. Higgins. and R. Gulliver. 1974. Instant
germination--a method of brinkmanship. Comm.
Grower. January issue.

Heydecker. V.. J. Higgins. and Y. J. Turner. 1975.
Invigoration of seeds? Seed Sci. and Technol.
3:881-888.

Hiltner. L.. and G. Essen. 1911. Ueber das schlechte
Auflaufen und die Auswinterung des Getreides infolge

befalls durch Eusdpium Ldnwdrtsch. Fb. Bayern
1:20-60. 231-178. 315-362.

Hoffman. C. A. 1933. Development morphology of Addipn
pepa L. Bot. Gas. 95:279-299.

102

Holm. G. 1954. Chlorophyll mutation in barley. Acta Agr.
Scand. 4:457-470.

Hopkins. E. F.. J. F. Rameris Silva. V. Pagan. and A. G.
Villafane. 1947. Investigation on the storage and
preservation of seed in Puerto Rico. Puerto Rico
Agr. Expt. Sta. Bul. 72:1-47.

International Seed Testing Association. 1966.
Determination of moisture content. Proc. Int. Seed.
Test Ass. 31(1):128~139.

Ivar Gadd. 1950. Biochemical tests for seed germination.
Proc. Int. Seed. Test Assoc. 16:234-253.

James. E. 1967. Preservation of seed stock. Advances in
Agronomy 19:87-106.

Jones. D. E.. J. P. Divine. and C. E. Gersdorff. 1942.
The effect of storage of corn on the chemical
properties of its protein and its growth promoting
value. Cereal Chemistry 19:819-830.

Jones. E. A. and L. R. Mann. 1963. Onion and their
allies. Iorld Crops Books. Leonard Hill Ltd.
London.

Jones. H. A. and J. T. Rose. 1928. Truck crop plants.
McGraw Hill. New York.

Justice. 0. L. and L. N. Haas. 1978. Principles and
practices of seed storage. USDA Agr. Handbook 506.

Raloyereas. S. A.. I. Mann. and J. C. Miller. 1961.
Experiments in preserving and revitalising pine.
onion. and okra seeds. Eco. Bot. 15:213-217.

Rhan. A. A.. R. L. Tao. J. S. Rnypl. and B. Borkowska.
1978. Osmotic conditioning of seeds: Physiological
and biochemical changes. Acta Horticulturae
83:267-278.

Rondo. M. and T. Okamura. 1931. Storage of rice. V. on
the influence of desiccating materials upon the
preservation of the germinating power of hulled rice
having different moisture contents on stored at
different temperatures. Ohara Inst. of Land I.
Forsch. Ber. 5:221-242.

103

Roostra. P. T. and J. F. Harrington. 1969. Biochemical
effects of age on membranal lipids of Cpgumip
pativus L. seeds. Proc. Int. Seed. Test Assoc.
34:329-340.

Rosar. V. F. and R. C. Thompson. 1957. Influence of
storage humidity on dormancy and longevity of
lettuce seed. Proc. Amer. Soc. Hort. Sci.
70:273-276.

Lakon. G. 1954. Derkeimwest dernackten Raryopsen in Seat
gut von Hofer und Timothee. Seatgutwirtschaft
6:259-262.

Larson. L. A. 1968. The effect of seeking pea seeds with
or without seed coat on seedling growth. Plant
Physiol. 43:255-259.

Levitt. J. and P. C. Hamm. 1943. A method of increasing
the rate of seed germination of Tpraxacum
godsaghyg. Plant Physiol. 18:288-293.

Lewis. D. 1953. Seed storage. John Innes Hort. Inst.
Ann. Rep. 43:14-15.

Lightburn. D. J. 1976. Osmotic pretreatment of tomato
seeds and their subsequent growth. University of
Nottingham. B.Sc. (Hons.) dissertation.

Liley. P. E. And V. R. Gambill. 1973. Physical and
chemical data. pp. 1-250. In: R. H. Perry and C.
H. Chilton (eds.). Chemical Engineers' Handbook.
McGraw Hill Inc.. New York.

Lougheed. E. C.. D. P. Murr. P. M. Harney. and J. T.
Sykes. 1976. Low pressure of seeds. Experientia
32:1159-1161.

MacRay. D. B. 1972. The measurement of viability.
pp. 172-208. In: E. H. Roberts (ed.). Viability
of seeds. Chapman and Hall Ltd.. London.

McRay. J. V. 1961. How seeds are formed. pp. 11-26. In:
Alfred Strefferud (ed.). Seeds. The Yearbook of
Agriculture. USDA. 'ashington. D. C.

McDonald. M. B. 1975. A review and evaluation of seed
vigor tests. Proc. Assoc. Off. Anal. 65:109-139.

McDonald. M. B. 1980. Assessment of seed quality. Hort.
Sci. l5(6):784-788.

104

McDonald. M. B. and D. O. Vilson. 1979. An assessment of
standardisation and ability of the ASA 610 to
rapidly predict potential soyabean germination. J.
Seed. Technol. 4(2):1-11.

Mexal. J.. J. T. Fisher. J. Osteryoung and P. C. P. Reid.
1975. Oxygen availability in polyethylene glycol
solutions and its implications in plant water
relationships. Plant Physiol. 55:20-24.

Michel. B. E. and M. R. Raufmann. 1973. The osmotic
potential of polyethylene glycol 6000. Plant
Physiol. 51:914-916.

Moore. R. P. 1972. Effects of mechanical injuries on
viability. Pp. 94-113. In: E. H. Roberts (ed.).
Viability of seeds. Chapman and Hall. Ltd.. London.

Moss. H. J.. N. F. Derera. and L. N. Balsam. 1972. Effect
of preharvest rain on germination in the ear and
~amylase activity of Australian wheat. Austral.
Jour. Agr. 23:769-777.

Murata. M. 1979. Genetic changes induced by artificial
seed aging in barley. Ph.D. dissertation. Colorado
State University. Ft. Collins. U.S.A.

Nakamura. S. 1975. The most appropriate moisture content
of seeds for their long life span. Seed Sci. and
Technol. 3:747-759.

Nakamura 8.. T. Sato. and T. Mine. 1972. Storage of
vegetable seeds dressed with fungicide dusts. Proc.
Int. Seed Test Assoc. 37(3):961-968.

Nawaschin. M. and H. Gerassimowa. 1936a. Natur and
Ursaehen der Mutationen. 1. Das Verhalten and die
Zytologie dere Pflansen. die as infolge Alterns
mutierten Reimen Stammen. Cytologia 7:324-362.

Nawaschin. M. and H. Gerassimowa. 1936b. Natur and
Ursaehen der Mutationen. III. Ueber die
chromosomen Mutationen. die in den Zellen von
ruhender Pflansenkeimen bei deren Alterm
auftereten. Cytologia 7:437-465.

Newhall. A. G. and J. R. Hoff. 1960. Viability and vigor
of 22 year old onion seeds. Seed Vorld 86(12):4-5.

Nobbe. F. 1876. Handbuch dere Samenkinde. Viegand.
Hempel and Parey. Berlin.

105

Nutile. G. E. 1964. Effect of desiccation on viability of
seeds. Crop Science 4:325-328.

Orchard. T. J. 1977. Estimating the parameters of plant
seedling emergence. Seed Sci. and Tech. 6:61-69.

Osborne. D. J.. B. E. Roberts. R. J. Payne. and S. Sen.
1974. Protein synthesis and viability in rye
embryos. Pp. 805-812. In: R. L. Bieleski. A. R.
Ferguso. and M. M. Cresswell (eds.). Mechanisms of
regulation of plant growth. Bull. 12. The Royal
Soc. of New Zealand. Iellington.

Owen. E. G. 1956. The storage of seeds for maintenance of
viability. Commonwealth Agricultural Bureau of
Pasture and Field Crops. Bull. 43. 81 pp.

Oxley. T. A. 1948. The scientific principles of grain
storage. Northern Publishing Co.. Liverpool.

Peterson. A. V. Schlegel. and B. Hummel. 1956. Grain
storage studies XXII. Influence of 03 and C03
concentration on mold growth and grain
deterioration. Cereal Chemistry 33:53-66.

Pollock. B. M. 1961. The effects of production practices
on seed quality. Seed Iorld 89(5):6. 8. 10.

Pollock. B. N.. and E. E. Roos. 1972. Seed and seedling
vigor. Pp. 313-387. In: T. T. Roslowski (ed.)
Seed Biology. Academic Press. New York.

Roberts. E. H. 1972a. Introduction. Pp. 1-13. In E. H.
Roberts (ed.). Viability of seeds. Chapman and
Hall Ltd.. London.

Roberts. E. H. 1972b. Storage environment and control of
Viability of seeds. Chapman and Hall Ltd.. London.

Roberts. E. H. 1972c. Cytological. genetical and
metabolic changes associated with loss of
viability. Pp. 253-306. In: E. H. Roberts (ed.).
Viability of seeds. Chapman and Hall. Ltd.. London.

Roberts. E. H. and F. H. Abdella. 1968. The influence of
temperature. moisture and oxygen on period of seed
viability in barley. broadbean and pea. Ann. Bot.
32:97-117.

106

Roberts. E. H. and R. H. Ellis. 1982. Physiological.
ultrastructural and metabolic aspects of seed
viability. Pp. 465-485. In: A. A. Rhan (ed.).

The physiology and biochemistry of seed development.
dormancy and germination. Elseview Biomedical
Press. Amsterdam. The Netherlands.

Rocha. F. F. 1959. Interaction of moisture content and
temperature on seed viability. Proc. Amer. Soc.
Hort. Sci. 73:385-389.

Roos. E. E. 1980. Physiological. biochemical and genetic
changes in seed quality during storage. Hort. Sci.
l5(6):781-784.

Rossman. E. C. 1949. Freesing injury of maise seed.
Plant Physiol. 24:629-656.

Salisbury. F. B. and C. Ross. 1978. Plant physiology.
2nd ed. Vadsworth Publishing Co.. California.

Salter. P. J. and R. J. Darby. 1976. Synchronisation of
germination of celery seeds. Ann. Appl. Biol.
84:415-424.

Seminuik. G. 1954. Microflora. Pp. 71-151. In: J. A.
Anderson and A. I. Alcock (eds.). Storage of cereal
grains of their products. Published by American
Association of Cereal Chemists. St. Paul. Minn.

Shanda. H. L.. D. C. Janisch. and A. D. Dickson. 1967.
Germination response of barley following different
harvesting conditions and storage treatments. Crop
Sci. 7:444-446.

Simon. E. V. and R. M. Rajaharun. 1972. Leakage during
seed imbibitiom. J. Expt. Bot. 23(77):1076-1085.

Standwood. P. C.. M. I. Brown. and E. E. Roos. 1978.
Freesing damage of high moisture lettuce seeds.
AOSA Newsletter 52:38-39.

Standwood. P. C. and E. E. Roos. 1979. Seed storage of
several horticultural species in liquid nitrogen
(~196°C). Hort. Sci. 14(5):628-630.

Struvc. I. M. 1959. Drying and germinability of maise.
Dissertation Abst. 19:2222.

107

Tao. R. L.. A. A. Rhan. G. E. Herman and C. J. Eckenrode.
1974. Practical significance of application of
chemicals in organic solvent to dry seeds. J. Amer.
Soc. Hort. 99(3):217-220.

Tao. R. J. 1978 Factors causing variation in the
conductivity test for soyabean seeds. Journal of
Seed Technology 3(1):10-19.

Thill. D. C.. R. D. Schirman. and A. P. Appleby. 1979.
Osmotic stability of mannitol and polyethylene
glycol 20.000 solutions used as seed germination
media. Agron. J. 71:105-108.

Thompson. E. C. and O. Smith. 1938. Seed stalk and bulb
development in the onion. Bull. Cornell Agric. Exp.
Ste. 708. 21 pp.

Thomson. A. G. 1952. Grain storage in tropical and other
climates. New Commonwealth 23(1):23-25.

Toole. E. H. and V. R. Toole. 1946. Relation of
temperature and seed moisture to viability of stored
soyabean seed. USDA Circular 753:1-9.

Toole. E. H. and V. R. Toole. 1953a. Relation of storage
conditions to germination and to abnormal seedlings
in beans. Proc. Int. Seed Test. Assoc. 18:123-129.

Toole. V. R. and E. H. Toole. 1953b. Seed dormancy in
relation to seed longevity. Proc. Int. Seed Test.
Assoc. 18:325.

Turner. Y. T. 1977. Osmotic treatment of onion (Allipm
pope L.) seeds. Ph.D. thesis. University of

Nottingham.

Villiers.,T. A. 1973. Aging and longevity of seeds in
field conditions. Pp. 265-288. In: I. Heydecker
(ed.). Seed Ecology. Pennsylvania State University
Press. University Park.

Villiers. T. A. and D. J. Edgcumbe. 1975. On the cause of
seed deterioration in dry storage. Seed Sci. and
Technol. 3:761-774.

Ueibull. G. 1952. The cold storage of vegetable seed and
its significance for plant breeding and the seed
trade. Agr. Hort. Genet. 10:97-104.

108

Veibull. G. 1955. The cold storage of vegetable
seeds--further studies. Agr. Hort. Genet.
13:121-142.

Veibull. G. 1956. The cold storage of vegetable
seeds--further studies. Int. Hort. Congr. Rep.
14:647-667.

Ihite. D. G. 1947. Longevity of bamboo seeds under
different storage conditions. Trop. Agr. (Trinidad)

Vhite. J. 1909. The ferments and latent life of resting
seeds. Roy. Soc. London Proc. 81(550):417~442.

Voodstock. L. w. 1969. Biochemical tests for seed vigor.
Proc. Int. Seed Test. Assoc. 34:253-263.

Voodstock. L. V. 1973. Physiological and biochemical
tests for seed vigor. Seed Sci. and Technol.
13127-157e

Ioodstock. L. I. 1976. Progress report on the seed vigor
testing handbook. AOSA Newsletter 50:l~78.

Voodstock. L. N.. S. Mason. R. Paul. and L. Haas. 1983.
Use of freese drying and acetone impregnation with
natural and synthetic anitoxidants to improve
storability of onion. pepper and parsley seeds. J.
Amer. Soc. Hort. 108(5):692~696.

Vortman. L. D. and E. H. Rimke. 1951. Seed corn injury
and various stages of processing and its effect upon
cold test performance. Agron. J. 43:299-305.

Zeleny. L. 1959. Chemical. physical and nutritive changes
during storage. Pp. 46-76. In: J. A. Anderson and
A. I. Alcock (eds.). Storage of cereal grains and
their products. Published by American Association
of Cereal Chemists. St. Paul. Minn.

"ITilllllllllllllllf