ASSIGNMENT ON

SEED VIABILITY, DORMANCY AND STORAGE

PRESENTING BY SUSHEEL KUMAR Id.NO-48008

SEED VIABILITYSEED VIABILITY- “Seed viability refers to the capability of a seed to germinate and produce a normal seedling.”

“The viability of the seed accession is a measure of how many seeds are alive and could develop into plants which will reproduce themselves, when given the appropriate conditions.”

(Copeland and Mc Donald, 1980)

VIABILITY OF SOME VEGETABLES SEED

SEED LOOSE VIABILITY DUE TO

Seed loose viability due to adverse weather conditions during seed development and maturation e.g. drought, excess water, extreme temperature etc.

Nutrient deficiencies and pesticides injury during seed development and maturation.

Environmental conditions after physiological maturity e.g. during harvesting, drying, cleaning, storage and handling of seeds.

SEED VIABILITY TESTS

Tetrazolium test ( Tz ) Germination test Cut test X-ray analysis Spectral imaging . Ferric Chloride Test for Mechanical Damage . Indoxyl Acetate Test for Seed Coat Damage. Noninvasive diagnosis of seed viability using infrared

thermography.

TETRAZOLIUM TEST TETRAZOLIUM TEST (George Lakon in 1942) OBJECTIVE: “Rapid assessment of viability.”

PRINCIPLE: “A colorless tetrazolium solution is used as an indicator producing in living cells a red, stable and non-diffusible substance, named Formazan. Thus, it’s possible to distinguish the red colored living tissues from the colorless dead ones and the seeds are classified into viable and non viable seed classes.”

PRECONDITIONING OF SEED BEFORE TETRAZOLIUM (Tz) TEST

Preconditioing of seeds before Tetrazolium (Tz) test no moistening or preparation required (small seeded legumes with soft coats).

Seeds directly placed in Tz solution in case of peas and beans bisect longitudinally before placing in Tz solution.

Eg: The seed coat may be removed e.g. cucurbits The

seed coat may be scratched above embryo e.g. lettuce

METHODOLOGYSEED HYDRATION

It is done by soaking seeds in water for a specific period of time .

This is done to active hydrolytic enzyme (dehydrogenase) and stimulate respiration.

CUTTING OR PUNCTURING OF SEED

This is done to allow the penetration of Tz solution into internal tissues.

STAINING OF SEEDS

Staining of seeds: It is done by soaking seeds in Tz solution for a specific period of time to allow staining of viable tissue in the seed.

Tz is used @ 0.1 or 1.0 % solution, at 30-35º C temperature for 24-48 hours at pH of 6-8.

EVALUATION OF SEED Evaluation of seeds evaluated according to staining

pattern.

GERMINATION TEST

OBJECTIVE: To gain information about the field planting value of the seed lot.

GERMINATION : Germination in a laboratory test refer to the emergence from the seed embryo of those essential structures which for the kind or seed being tested; indicate its ability to develop into a normal plant under favourable conditions.

PHASES OF GERMINATION

Imbibition phase (Rapid uptake of water)

Active metabolism (Major metabolic pathways affected are respiration, protein synthesis, DNA replication, RNA synthesis etc.)

Cell expansion and seedling protrusion.

GENERAL REQUIREMENT FOR GERMINATION SUBSTRATUM

Suitable substratum : Paper, sand or soil . Adequate moisture/ water : pH 6-7.5,. Favourable temperature : as per crop . Light : Required for germination in some of the crops like lettuce etc. Chemicals : KNO 3 , GA 3 , Ethephon as prescribed by ISTA. Prechilling : Also called stratification and it is exposing of imbibed seeds to cool

temperature usually between 5-10 º C for a period of time (days, week or months) Duration of germination tests : Number of days to first and final count .

Germination Methods in the laboratory: Between the paper(BP method) Top of the paper (TP) Sand

PROCEDURE

From working sample take 400 seed at random.

Method Between Paper/ Top Paper / sand

Plant seed as 100×4R, 50×8R, 25×16R

Provide temperature or light and humidity as recommended.

Germination count(1st and final as per specie)

THE CUT TEST

The cut test is simple and easily executed.

Viability is determined by cutting the seed open and examining the contents.

In particular, the seed embryo must appear intact and healthy if the seed is to go on and germinate.

In addition, the endosperm must appear clean and firm.

X-RAY ANALYSIS

X-ray radiography is a valuable tool to supplement laboratory tests , provide additional information about the seed lot quality along with the internal detail/structure of the seed.

X-ray analysis can be a very efficient and non-destructive method of assessing seed quality.

A good x-ray image will reveal details of seed fill, insect infestation and also size or absence of the embryo.

SEED DORMANCY

SEED DORMANCY

Failure of fully developed & mature viable seed to germinate under favorable conditions of moisture & temperature.

- This condition called as resting stage, period or dormancy.

- This seed called as dormant seed.

TYPES OF DORMANCY

Primary dormancy-Due to internal causes even favorable

environmental conditions are available for germination.

Secondary dormancy-They germinate immediately after present the

favorable conditions, but the dormancy is induced in the seeds if there is kept under certain conditions.

Eg. Mustard seed – is kept in higher concentration with CO2 due to respiration.

Special dormancy-Some species are germinated , but the primary roots

fail to develop that’s why epicotyls is stopped.

Organic dormancy-Seed remains hard after the expiry of germination

period and don’t germinate, when the moisture reduced below 4%.

CAUSES OF DORMANCY

1. Impermeability of seed coat to water-

Seed coat become hard (family- Leguminosae, Solanaceae, Malvaceae, Convolvulaceae, Chenopodiaceae.) the seed contain external waxy coating made up off Lignin, Suberin or Cutin which is impermeable to water.

- These seed remain dormant until seed coat is removed by microbial activity of alteration of temperature.

2. Impermeability of seed coat to oxygen-

Germination is inhibit due to impermeability of the seed coat to oxygen.

Eg. Fruit of Oats and Xanthium-These contains two seed (upper & lower)

lower is germinate under soil and upper seed doesn’t germinate until seed coat is punctured or removed by the high concentration of oxygen.

3. Growth of embryo-

Mustard & Amaranthus- seed are easily permeable in oxygen and water, but the seed coat doesn’t rupture.

4. Immaturity of embryo-

The development of other parts of seed completed except embryo.

5. Temperature requirement-

Apple , Peach require low temperature to germinate further more require high temperature to germinate.

6. Light requirement-

Carrot, tobacco require absolute requirement of light, while Datura exposure to light is inhibitory for germination.

7.Germination Inhibitors-

Tomato fail to germinate due to presences cirulic acid found in the sap of fruits.

These chemical present the husk in Rice and Oats seed .

METHODS OF BREAKING DORMANCY

1.Mechanical treatment of seeds-The dormancy can be removed by mechanically to weakening the seed coat called as Scarification.

1) Filing (using sand)2) Chipping (using knife)3) Piercing (using needle)4) Chilling (using temperature)5) Pre-drying (using temperature)6) Pre-washing (using water)7) Pre-soaking (using warm water)

2. Chemical treatment-Seed are dipped in mineral acid (HCL,

H2SO4) or organic solvent (Alcohol, Acetone) to cause degrading of seed coat and dissolving of waxy coating.

3. Use of growth regulator-Germination can be influence by using

growth hormones (GA3, IBA, IAA, NAA, 2,4-D)

ADVANTAGES OF DORMANCY

Seed survive in adverse conditions.

Seed stored till next season, transport to another place without loosing its viability.

Seed use in research such as gene pool.

Some seed kept in cold condition to get best price when there is off season.

Due to dormancy species are saved from wipeout in case of natural calamity.

Seed germinate itself.

DIS-ADVANTAGES OF DORMANCY

The seed can not sown immediately after maturity, will have to wait for the expiry of dormant period.

Seed remain naked during dormant period they get shabby look.

Germination of the seeds is poor and growth of buds is slow and irregular even under favorable condition.

Noxious weed seed lie dormant for many years in soil and thus growing year after year becomes eradication impossible.

PURPOSE OF SEED STORAGE

The purpose of seed storage is to maintain the seed in good physical and physiological condition from the time they are harvested until the time they are planted .

GENERAL PRINCIPLES OF SEED STORAGE

Seed storage conditions should be dry and cool .

Effective storage pest control .

Proper sanitation in seed stores .

Before placing seed into storage they should be dried to safe moisture limits, appropriate for the storage system .

Storing of high quality seed only i.e well cleaned , treated as well as of

high germination with vigour and good pre-storage period .

SEED LONGEVITY IN STORAGE IS A FUNCTION OF:

Type of species

Initial seed quality (production and conditioning)

Storage environment

SPECIES CAN DISPLAY ORTHODOX AND RECALCITRANT BEHAVIOUR

ORTHODOX SEED:Orthodox seeds tolerate maturation drying and can remain viable for years.Medium-lived seeds (3 – 15 years). Long-lived seeds (> 15 years).

RECALCITRANT SEED: Recalcitrant seeds do not tolerate maturation drying and are short-lived seeds. Species can display orthodox or recalcitrant seed behavior

RELATIVE STORABILITY INDEX

Crop Category 1 (1 to 2 yr.)

Category 2 (3 to 5 yr.)

Category 3 ( >5 yr.)

VEGETABLES Green bean Broccoli & cabbage Beet

Lettuce Sweet corn Tomato

Onion Cucumber

Pepper Pea

STORAGE CONDITIONS

Seed longevity is improved by storing seeds at low temperature and low moisture content.

Rule of thumb for seed storage Seeds lose half their storage life:

1.For each 1% increase in seed moisture between 5 and 14%. 2.For each 5ºC increase in storage temperature between 0 and 50ºC.

TYPES OF STORAGE

Sealed containers

Open storage

Conditioned storage

SEALED CONTAINERS:

Used to keep out moisture Types include: Aluminum or plastic cans Aluminum pouches

CONTI……

Plastic bottles

Waxed boxes

Laminated paper bags

OPEN STORAGE

Does not have temperature or relative humidity control.

Cheapest type of storage. Needs basic protection from water, contaminating agents (herbicides), and rodents.

CONDITIONED STORAGE

Conditioned storage as temperature control.

Commercial storage facilities held at <10ºC.

Humidity may be controlled below 50% RH or seeds stored in sealed containers.

Conditioned storage is used for high value seeds.

Thank you