Essay on Seed (3206 Words)

Read this essay to learn about Seed of a Plants. After reading this essay you will learn about: 1. Meaning of the Seed 2. Characteristics of the Seed 3. Classification 4. Germination 5. Methods for Viability Test 6. Dormancy 7. Seed Treatment 8. Seed Certification.

Contents:

1. Essay on the Meaning of the Seed
2. Essay on the Characteristics of the Seed
3. Essay on the Classification of Seed
4. Essay on Germination
5. Essay on the Methods for Viability Test
6. Essay on Dormancy
7. Essay on Seed Treatment
8. Essay on Seed Certification

Essay # 1. Meaning of the Seed:

i. May be defined as “a fertilized ovule consisting of intact embryo, stored food and seed-coat which is viable and has got the capacity to germinate.”

ii. “Seed is any material used for planning & propagation whether it is in the form of seed (grain) of food, fodder, fiber or vegetable crop or seedlings, tubers, bulbs, rhizomes, roots, cuttings, grafts or other vegetatively propagated material.”

First private seed company – Sutton and Sons (existence in 1912 in Kolkata)

Essay # 2. Characteristics of the Seed:

i. It must be true to its type.

ii. The seeds must be healthy, pure and free from all inert materials and weed seeds.

iii. The seeds must be viable.

iv. The germination capacity is up to the standard and it has been tested recently.

v. The seeds must be uniform in its texture, structure and look.

vi. The seeds should be truthfully, labelled and produced under all due cares.

vii. The seed must not be affected by any seed-borne disease.

viii. It should be dry & not mouldy and should contain 12-14% moisture.

Seed health refers that the seed is free from any kind of disease prologue (spore, mycelium, etc.), either active or latent.

Essay # 3. Classification of Seed:

i. Breeder/Nucleus Seed:

(a) These seeds are produced at breeder’s level as a result of hybridization selection and mutation.

(b) When these seeds possess all the required genetic characters they are named as breeder’s or nucleus seeds.

(c) For testing the genetic purity, yield potentials, disease reaction and adaptability, the seed has to go for testing under a number of trials in different agro-climatic conditions or zones of the country.

(d) Each breeder’s seed has to be tested in Initial Evaluation Trial, National Trial, Uniform Regional Trial, and District Trial and finally under Mini-Kit programme and the varieties which qualify in all the trials are further produced.

(e) These seeds are 100 per cent pure and being very little in quantity are often costly.

(f) Golden yellow tag denotes breeder seed.

ii. Foundation Seed:

(a) The foundation seed is a second grade seed in order of its genetic purity.

(b) The foundation seed is always produced by certain organizations viz. National Seed Corporation, Tarai Development Corporation and State Seed Corporation.

(c) A strict seed plot technique which includes inspection, rouging, weed control, isolation etc., is adopted during seed production process.

(d) The foundation seed is relatively less pure compared to the breeder’s or nucleus seed.

(e) White tag denotes foundation seed.

iii. Certified Seed:

(a) Progeny of foundation or registered or certified seed itself.

(b) It is approved and certified by the state seed certifying agency, annually produced by progressive farmers according to standard seed production practices.

(c) It is available for general distribution to farmers for commercial crop production.

(d) It is generally produced by SSC.

(e) Two classes of CS are produced i.e. F₁ and F₂.

(f) Recertification is not permitted from F₁ generation (second) of seeds.

(g) It has Azure blue tag.

iv. Registered Seed:

(a) Produced from FS or Registered seed itself.

(b) It is the parent of certified seed or RS.

(c) It has satisfactory genetic identity and purity and is usually produced by progressive farmers under technical guidance and supervision from SSC.

(d) It has purple tag.

v. Truthfully Labeled Seed:

(a) It is the seed offered for sale after testing germination percentage and physical purity etc.

(b) It is not a certified seed, as there is no inspection carried out by the certified person.

Essay # 4. Germination of Seed:

Meaning of Germination of Seed:

A. Germination is the emergence and development of seedlings from the seed-embryo which is able to produce a normal plant under favorable condition.

B. Agronomically, germination means the capacity of seeds to give rise to normal sprouts within a definite period fixed for each crop under optimum field conditions.

Changes during Germination:

i. Swelling of seed due to imbibition’s of water by osmosis.

ii. Initiation of physiological activities such as respiration & secretion of enzyme.

iii. Digestion of stored food by enzymes.

iv. Translocation & assimilation of soluble food.

When seed is placed in soil gets favorable conditions, radical grows vigorously & comes out through micro Pyle & fixes seed in the soil. Then either hypo or epicotyls begins to grow.

Types of Germination of Seed:

i. Hypogeal germination: The cotyledons remain under the soil. E.g.: cereals, gram.

ii. Epigeal germination: The cotyledons pushed above the soil surface. E.g.: mustard, tamarind, sunflower, castor, onion.

Germination tests are always carried out with the seeds counted off at random from the pure fraction of seeds. In accordance with the I.S.T.A. rules, a minimum number of 400 seeds are required for germination test.

Essential factors for germination of seeds are (i) Moisture (ii) Temperature (iii) Oxygen-supply.

Methods for Testing Germination of Seed:

i. Petridish Method:

Two blotters or filter papers are placed on the bottom of the petridish and they are soaked with water. A convenient number of seeds, ranging from 10-20, are placed on the surface of water-soaked blotters in the petridish. The kind of seed, date and time of seed soaking are written on the glass-cover of petridish with the help of a glass marking pencil.

Usually, the germination percentage is calculated in two counts and reported on the basis of the results of germination of about 100 to 200 seeds. This method is suitable for small seeds viz. tobacco, tomato, radish, knol-khol, cabbage, cauliflower, mustard, lettuce, brinjal, chilies, etc.

ii. Rolled Towel Method:

Two wet towels are placed on a smooth table top. The appropriate numbers of seeds is placed on the upper surface of the towels and are covered by two wet towels. A fold is made of the bottom of the towel to prevent the seeds from falling out. The towels are then rolled from right to left.

The full information’s regarding the test i.e. the kind of seed, lot number, date and time of seed soaking are noted on the roll with the help of an indelible pencil. This method is suitable for comparatively large sized seeds viz. maize, wheat, pea and gram.

iii. Folder Paper Towel Method:

Two wet paper towels (big bamboo sheets), specially made for germination test, and are placed on the working table-top. The surface of paper-towel is marked into two halves. The right half of the towel surface is planted with seeds and the left side half is folded to cover the right half and information’s regarding the seed sample, date and time of seed soaking are written on the fold with an indelible pencil.

Water is frequently sprinkled on these towels and observations on germinating seedlings and their numbers are taken periodically. This method of germination test is convenient for relatively large sized seeds.

iv. Sand Method:

Seeds are planted in uniform layer of moist sand and then covered to depth of 1- 2 cm with sand. Substrates for germination are moistened with 0.2% KNO₃ solution.

v. Rags or Gunny Sacs Method:

The seeds are simply wrapped in a moistened rag or gunny sac, which is then rolled and tied loosely in the form of bundle. This is now kept at a proper temperature on a rack or convenient place for germination. The rolls are opened after a fixed period of time and the number of germinated seeds is counted.

vi. Mechanical Method:

In this method, apparatus like Germinators are used. Cabinets of the incubator type with thermostatically controlled temperature may be used for the purpose. In these cabinets the seeds may be placed evenly on moist filter paper in petri dishes or between filter papers kept moist by folds of moistened flannel or large seeds may be sown in dishes containing sand or fine soil.

Adequate water is applied when needed by the help of a wash-bottle or sprayer.

Seed Purity:

The purity of seed denotes the real percentage of desirable seed from a lot of seed with several impurities i.e. seeds of other varieties, other crop seed, defective seeds, weeds seeds, inert matter, sand straw, stones, soil and iron particles, pebbles etc.

Dockage is the impurity percentage of seed.

Essay # 5. Methods for Viability Test of Seeds:

Electrical Conductance Method:

a. The seeds are soaked in distilled water and the electrical conductance of the bathing solution is tested, the increase in conductance is roughly proportional to the percentage of dead tissues.

b. The increase in the conductivity is due to leaching of metabolites from dead seeds which become pervious owing to increasing permeability.

Potassium Permanganate Method:

a. The seeds are soaked in a weak solution of potassium permanganate and as the proportion of dead seed increases the discolouration of the solution also increase.

b. The dead cells become freely permeable to their contained solutes which leach out easily into bathing solution, whereas leaching from living cells is very less.

c. Thus, extent of discolouration indicates the proportion of dead seeds into a seed-lot.

Indigo Carmine Method:

a. The seeds are soaked in the solution of any aniline dyes such as indigo carmine for few hours; it is observed that the dead seeds or their cells are stained.

b. Thus, the portion of dead and viable seeds can be determined by counting the number of stained and unstained seeds respectively.

Embryo Culture Method:

a. In this method, the embryo is removed carefully from its cotyledons or endosperm and then it is placed naked on granulated peat mass or on sterilized nutrient agar medium (White’s nutrient medium).

b. The method takes about 7 to 10 days to give the viability percentage of the seeds.

c. The viability is judged by counting the number of germinated embryos because the viable seeds will germinate and non-viable will fail to do so.

Tetrazolium Chloride Test:

a. The tetrazolium chloride test is also known as “Biochemical test”.

b. In this method the seeds are soaked in 0.5 to 2% solution of tetrazolium chloride (2, 3, S-triphenyl tetrazolium chloride).

c. The viable or living seeds take bright red colouration which becomes more intense in the embryo while the dead seeds remain in their original colour.

d. The method can be used as a guide in blending seeds and their lots under an urgent and immediate demand for seed.

e. First Seed Testing Laboratory was established at IARI in 1961.

Essay # 6. Dormancy of Seed:

Causes of Dormancy:

i. Seed coats being impermeable to water

ii. Hard seed coat

iii. Seed coats being impermeable to oxygen

iv. Rudimentary embryo of seeds

v. Dormant embryo

vi. Synthesis and accumulation of germination inhibitors in the seeds

Kinds of Dormancy in Seeds:

i. Primary dormancy:

The seeds which are capable of germination just after ripening even by providing all the favorable conditions are said to have primary dormancy. E.g.: Potato.

ii. Secondary dormancy:

Some seeds are capable of germination under favourable conditions just after ripening but when these seeds are stored under unfavorable conditions even for few days, they become incapable of germination.

iii. Special type of dormancy:

Sometimes seeds germinate but the growth of the sprouts is found to be restricted because of a very poor development of roots & coleoptiles.

Methods to Break the Seed Dormancy:

i. Scarification:

The dormancy due to hard seed coat or impermeable seed coats can be broken by scarification of seed coats. It should be done in such a way that the embryo is not injured.

(a) Chilling (Pre-chilling):

The seeds are placed in contact with the moist substratum at a temperature of 5 to 10°C for 7 days for germination, e.g. Cabbage, Cauliflower, and Sunflower.

(b) Pre-dying:

Seeds should be dried at a temperature not exceeding 40°C with free circulation for a period of 7 days before they are placed for germination. E.g. Maize, Lettuce.

(c) Pre-washing:

In some seeds, germination is affected by naturally occurring substances which act as inhibitors which can be removed by soaking & washing the seeds in the water before placing for germination. e.g. Sugar beet.

(d) Pre-soaking:

Some seeds fail to germinate due to hard seed coat. Such seeds should be soaked in warm water for some period so as to enhance the process of imbibition’s, e.g. Chili, Subabul.

(e) Rubbing or puncturing seed coat:

Some seeds are subjected to mechanical scarification either by rubbing them against rough surface or puncturing the seed coat with pointed needle. E.g. Coriander, Castor.

(f) Application of pressure to seeds:

Germination of Medic ago sativa is found to be increased when a hydraulic pressure of 2000 atmosphere at 18°C is applied. It may be due to increase in permeability of seed coat to water and O₂.

ii. Stratification:

In some seeds after ripening, low temperature and moisture conditions require in artificial stratification. Seed layer altered with layers of moist sand or appropriate material to store at low temperature, e.g. Mustard & Groundnut.

iii. Exposure of seeds to light:

It also helps to break the dormancy & increase the germination.

iv. Chemical treatments:

(a) Potassium nitrate treatment (KNO₃) the material used for placing the seeds for germination i.e. substratum, may be moistened with 2% solution of KNO₃ (2g KNO₃ + 100ml of water). E.g. rice, tomato, chilies.

(b) Gibberellic acid treatment: The substratum used for germination may be moistened with 500 ppm solution of GA i.e. 500 mg in 1000ml water. e.g. Wheat, Oat.

(c) Thio-urea treatment: Potato tubers are dipped in thio-urea solution (1%) for one hour when fresh harvested produce is to be used as seed material.

Essay # 7. Seed Treatment:

Meaning of Seed Treatment:

“Seed treatment is a process of application of chemicals or protectants (with fungicides or bactericides or nematicides) to seeds that prevent the carriage of insects or diseases causing pathogens in/on the seeds. Seed treatment also enables the seed to overcome seedling infection by soil-borne fungi.”

Objectives of Seed Treatment: 

i. To control disease: by treated the seeds with fungicides or organo mercurial compounds like Thirum, captain, carbendazim, agrosan, cereson, etc. E.g. to control paddy blast, seed is to be treated with agrosan @ 3 g per kg (3g/ kg) of seed).

ii. To have convenience in sowing due to special characteristics of the seed like fuzz of cotton seeds, coriander seeds, small seeds of chili, ragi, bajara, etc. E.g. coriander seed is to be splitted by rubbing it against hard surface. Seed of chili, Sesamum, bajara are mixed with fine sand or soil.

iii. To have quick germination with broken thick seed coat by mixing them with coarse gritty sand & trampling or pounding it lightly in a morter with a wooden pestle for breaking the thick seed coat or soaked the seeds in water for a specified time, e.g.: cotton seed or paddy seed is soaked in water before actual sowing.

iv. To increase nitrogen fixation in legumes: Legume seeds are inoculated with a particular Rhizobium culture. This is mixed with jaggery solution & applied to seed and dried in shade. It increases nodulation & thereby N fixation.

v. To protect the seed against insect pests:

vi. To induce earliness (Vernalization treatment).

7. To break dormancy by treating seed with chemicals, e.g. Thiourea 1% treatment to potato tubers.

Application of Seed Treatment in Important Crops:

i. Sorghum:

Thirum or 300 mesh sulphur: Seed is coated in seed dressing drum or earthen pot @ 3.4 g/kg seed against smut disease.

ii. Bajara:

Brine solution treatment is given @ 20% against eat got and to discard light & diseased seed.

iii. Paddy:

Seed is treated with brine solution @ 3% against blast of paddy and to discard unfilled seed.

iv. Wheat & Oilseed crops:

Seed is coated with Thirum or Bavistin @ 5 g/kg seed against seed borne diseases.

v. Cotton:

Seed is treated with organo mercurial compound like Ceresan, Agrosan @ 3 g or Thirum @ 5g against seed borne disease like anthracnose.

vi. Small seeded crops like Sesamum, bajara, tobacco, etc.: Seed is mixed with fine sand or soil for even sowing of seed in the field.

vii. Potato:

(a) Seed is dipped in 1% Thiourea solution for breaking the seed dormancy.

(b) Seed is dipped in streptomycin solution @ 200 g in 100 lit. Water for 1 hour against Ring rots disease.

viii. Legume crops like Mung, Urd, Soybean etc.

(a) Seed is treated with Thirum @ 3 g/kg seed against seed borne disease;

(b) Seed is treated with Rhizobium culture @ 250g/10kg seed for ‘N’ fixation & better nodulation.

ix. Sugarcane:

(a) Hot water treatment (50°C) or hot air treatment (54°C) is given to sets for 2 hrs. Against grassy shoot & other diseases,

(b) Sets are treated with OMC 6% @ 500g in 100 lit. Water by dipping for 5 min. against smut & increase germination or Bavistin @ 200g in 100 lit. for 5 min.

Essay # 8. Seed Certification:

Role of Seed Certification:

i. Field inspection:

At the time of growing a crop for seed production purpose. The data should be obtained on trueness to varietals purity, isolation of seed crop to prevent crops- pollination, mechanical admixtures and diseases dissemination, objectionable weeds and admixtures.

ii. Supervision on agricultural operations i.e. intercultural operations, harvesting, storage, transport and processing etc. for identity and quality of lots.

iii. Sample inspection:

For quality and to maintain genetic purity, a lab test of representative samples drawn by the S.C.A. for determining, percentage of germination moisture content, weed seed content, admixture and purity.

iv. Bulk inspection:

For checking homogeneity of the bulk as compared with the sample inspected.

v. Control Plot Testing:

Samples drawn from the source seed and the final seed produced can be grown in the field along with standard samples of the variety.

The purpose of seed certification is to maintain and make available high quality seed and propagating materials of notified plant varieties.

Phases of Seed Certification:

i. Verification of seed source.

ii. Inspection of seed crop in the field.

iii. Supervision at post-harvest stages including processing and packing.

iv. Seed sampling and analysis.

v. Grant of certificate, certification tag, tables and sealing.

A . National Seed Corporation (NSC): registered in 1963

Objectives:

i. To promote development of a seed industry in India.

ii. To produce and supply foundation seeds of various crops.

B. State Seed Farm Corporation (SSFC) was set up during 1969, which mainly concerned with production and supply of certified seed.

C. State Seed Certification Agency is responsible for seed certification. SSCA makes field inspections and conducts seed tests required for seed certification.

D. The seed Act – on 29 Dec, 1966

E. The seeds Rule – in 1968.

F. National Seed Programme -1975

G. National Seed Project -1988