Compilation of experiments on seed technology for school and college students.
Contents:
- Experiment on Seed Sampling
- Experiment on Physical Purity Analysis by Weight
- Experiment on Distinguishing Varieties Test (ODV)
- Experiment on Seed Germination Test
- Experiment on Biochemical Test for Viability
- Experiment on Determination of Seed Moisture Content
- Experiment on Determination of Seed Moisture Content
- Experiment on Seed Vigour Test
- Experiment on Seed Vigour (Electrical Conductivity Test)
- Experiment on Seed Treatment
- Experiment on Seed Priming
- Experiment on Seed Pelleting
- Experiment on Seed Packaging
- Experiment on Seed Marketing
1. Experiment on Seed Sampling:
Objective:
To obtain a sample of required quantity representing the seed lot in true sense.
Equipment’s and Materials:
Terrier, plastic tubes, bags, balance, seed divider, sticker and labels.
Primary Sample:
It is a small quantity of seed taken from one point of the processed lot. The seed lot is arranged to approach conveniently upto individual container. Primary samples are taken from different portions and depth by inserting the stick trier with the closed slot diagonally in the seed bag or container up to desirable depth with minimum damage to seed. The flow of seed is facilitated in the tube by opening and closing of the slot. Finally, the slot is closed, the terrier is withdrawn and collected sample is transferred to a container.
Composite Sample:
Primary samples drawn from different places of a lot are mixed and the mixture is known as composite sample. The size of composite sample should be 10 times more than the required submitted sample.
Submitted Sample:
The required quantity of seed which is sent to seed testing lab is known as submitted sample. To prepare a submitted sample, the composite sample is mixed thoroughly and reduced upto required quantity with the help of seed divider or by repeated halving method.
In repeated halving method, composite sample is spread uniformly on a clean and smooth surface. It is divided into two equal parts and one part is again thoroughly mixed and division is repeated to get the required quantity of submitted sample.
Working Sample:
A reduced sample taken from the submitted sample in the laboratory used in a given quality test.
Preparation of a Working Sample:
i. Repeated Halving Method:
As described for preparation of submitted sample, the seed is poured on a clean smooth surface and shaped as a mound after through mixing. Mound is divided into two halves, each half is again halved, each portion is again halved giving total 8 portions. Alternate portions are combined i.e. 1st and 3rd of first row and 2nd and 4th of second row. The remaining portion is kept in a pan and the process is repeated to obtain required size of working sample.
ii. Random Cup Method:
Six to eight small cups of equal size and shape are arranged at random on a tray. The seed is poured uniformly over the tray. The seeds, which fall into the cups are collected as working sample. This method is useful for the crops with small seed size but not for chaff and round seeds.
iii. Spoon Method:
The seeds are poured evenly in one direction over the tray. If required seed can be poured second time in opposite direction. Shaking of the tray is avoided. Small quantities of seeds are collected with the help of spatula from minimum 5 random places to make a working sample of required quantity.
The working sample is kept in paper bag marked with code number, name of the crop and purpose.
2. Experiment on Physical Purity Analysis by Weight:
Objective:
To determine the physical purity of a seed lot by weight of the other matter than the crop seed present in the working sample. The working sample is separated into pure seed, other seed and inert matter.
Material Required:
Physical/precision balance, purity work board, spatula, forceps, cups, seed sample.
Procedure:
The working sample of desired weight is prepared and distributed evenly over the physical purity work board. Pure seed, other seed and inert matter are removed with the help of spatula and forceps and kept in different cups. Separation is done without use of any pressure and magnification except some grasses.
Calculation:
Physical purity analysis is based on the sum of the weight of different components and not on the original weight of working sample.
Minimum Certification Standard for Physical Purity Percentage by Weight:
3. Experiment on Distinguishing Varieties Test (ODV):
Objective:
To estimate the number of seed of other distinguishing varieties.
Apparatus and Other Requirements:
i. Physical purity work board
ii. Spatula
iii. Forceps
iv. Petridishes
v. Note book
vi. Seed sample
Procedure:
The seed sample is examined by visual observation for the expression of seed characters. The submitted sample is uniformly spread over the surface of the physical purity work board and observations on the characters are made. Seeds exhibiting differences in distinguishing characters are sorted out and separated in Petridish. The ODV seeds are counted and reported in number.
Result:
The actual weight of the submitted sample and number of ODV seeds stored out is reported after converting the values as per kg of seed.
4. Experiment on Seed Germination Test:
Objective:
To test the germinability of a seed lot.
Apparatus:
Paper towels, petriplates, seed germinator, water
Method:
Minimum 400 seeds from pure seed fraction of physical purity test are tested for germination as per following procedures:
i. Paper Towel Method (BP):
Moist towel is stretched on a clean table and on the upper side of the paper towel 50 seeds are arranged on its half portion containing 5 rows each of 10 seeds. About 3 cm space is left on lower and right side of the paper towel. Seeds are covered with remaining half portion of the towel and the right and lower portion is folded upward to close both the ends.
The paper towel is rolled from the right end, wrapped in a wax paper and the ends are tightened with rubber bands. This paper towel is placed vertically in a seed germinator with upward direction of open end.
ii. Petriplate Method (TP):
Three pieces of circular filter paper are placed in a petriplate. The filter paper is moistened with distilled water. With the help of forceps, 25 seeds are arranged on the top of the moist blotter. The closed petriplate is placed in a germinator.
Evaluation:
Each seedling is critically evaluated on the day prescribed for first count. Seedlings with all their essential structures normal or badly decayed are counted and removed. Remaining seeds and seedlings are left as such and evaluated on the day of final count.
Normal Seedling:
Well-developed root system, well developed shoot axis, specific number of cotyledons, and single primary leaf in monocot and two in dicot.
Abnormal Seedling:
Damaged seedling, deformed seedlings, decayed seedlings.
Ungerminated Seed:
Seed which do not germinate even up to the end of the test period.
These are of following types:
(i) Hard Seed:
They remain hard at the end of the test period because of no water absorption. Hard seed from family Leguminoseae and Malvaceae are considered as germinated, whereas, hard seeds of other families are considered as ungerminated abnormal seed.
(ii) Fresh Ungerminated Seed:
Seeds which are neither hard nor germinated but remain clean, firm and apparently viable at the end of the test period. This category is considered as ungerminated abnormal seed.
(iii) Dead Seed:
Seeds showing softness, discolouration, mouldy and decaying is considered as ungerminated abnormal seed.
Calculation:
Germination is expressed as percentage by number of normal seedling and the sum of the normal, abnormal and ungerminated seeds must be hundred.
5. Experiment on Biochemical Test for Viability:
Objective:
Quick estimation of viability of seed samples.
Principle:
A colourless solution of 2,3,5 triphenyl tetrazolium chloride (indicator) reacts with hydrogen released by the reduction process in living cell due to action of enzyme dehydrogenese. It produces a red, stable and non-diffusible substance triphenyl formazan to distinguish from the colourless dead ones.
One per cent solution (W/V) of tetrazolium chloride at pH 6.5-7.5 is made in water and stored in amber colour bottle.
Conditioning media – Blotter, paper towel or beaker
Cutting and piercing device – Razor blade, dissecting knives, and needles
Staining dishes – Watch glasses/petridishes
Medicine dropper – To remove tetrazolium solution after test period.
Magnifying devices – Hand lens and stereoscopic microscope.
Seeds are soaked in tap water overnight and are split longitudinally with the help of a blade so that a protein of embryo is attached with each half of the seed. One half of each seed is placed in a petridishe and covered with 1% aqueous solution of tetrazolium chloride for 4 hours. The seeds are then washed in tap water and the number of seeds in which the embryo is stained red is determined.
Calculation:
The result are reported as percentage of viable seeds in relation to total seeds tested by using following formula:
6. Experiment on Determination of Seed Moisture Content:
Objective:
To determine the moisture content of seed sample through oven dry method.
Apparatus:
Oven, desiccator, analytical balance, grinding machine with uniform speed which does not cause heating to grinding material, sieve with mesh size of 0.5 mm, 1.0 mm and 4.0 mm and glass or metal containers of 8 or 10 cm diameter with a tightly fitted cover.
Procedure:
Working sample- Moisture of the seed sample submitted in waterproof container is estimated by oven dry method.
Preparation of Sample:
Crop of large seed size is grounded before drying unless its high oil content makes it difficult. After grinding, the sample is passed through different size of sieves. Pre drying before grinding is recommended for the sample having more moisture content than minimum required percentage for moisture determination.
Pre dried material is kept exposed for 2 hrs before drying. For the container of 8 cm diameter 4-5g sample and for 10 cm diameter 10 g sample is weighted without exposing it for more than 30 second to the air.
Moisture Determination:
Container and its cover are weighted (M1). The sample is distributed evenly over the surface of the container and weight with the cover of container (M2). This container is placed in an oven at a temperature of 103 ± 2° C for 17 hrs. The drying period starts when the temperature of oven reaches at the required point.
At the end of the prescribed period, container is placed for cooling in a desiccator for 30-45 minutes. After cooling container is weighted with its cover and content (M3). Determination of moisture content at 103 ± 2° C is recommended at less than 70% relative humidity.
Calculation:
The moisture content as percentage by weight is calculated to one decimal place by the following formula:
Conclusion:
Seed lot with moisture content more than the minimum seed certification standard is failed or recommended for more drying.
7. Experiment on Determination of Seed Moisture Content:
Objective:
To determine the moisture content of seed sample through universal moisture meter.
Equipment:
Universal moisture meter: It is a machine with (i) Compression unit (ii) Moisture meter dial (iii) Thermometer (iv) Compression knob (v) Cups of different volume.
Procedure:
A representative sample of prescribed weight or volume is obtained and placed in the sample cup. It is fixed in the lower house of compression unit.
Meter is calibrated by pressing the button “cal” and “bell” with the help of calibration knob. Sample is compressed as per requirement with the help of compression knob and scale. At required compression the meter dial (M) is read by pressing the knob “Read” and “bell”.
Temperature (T) is observed by the thermometer fixed in between meter dial and compression chamber. On adjustment of both the reading mark of arrow on the outer reading of temperature dial indicates the moisture percentage.
Calculation:
Seed lot with moisture content more than the minimum seed certification standard is recommended for drying.
8. Experiment on Seed Vigour Test:
Objective:
Determination of seed vigour.
The sum of those properties of seed which determine the potential level of activity i.e., rapid and uniform production of healthy seedling and stand establishment under a wide range of field conditions is considered as seed vigour.
Methods for Determination of Seed Vigour:
1. Seed Size:
100/1000 seeds drown randomly and weight in grams. The seed lot with high seed weight is considered as vigorous.
2. Seedling Length:
Length of 10 normal seedlings grown in moist towel paper kept at optimum temperature is measured in cm on the day of final count. The lot showing maximum seedling length is considered as vigorous.
3. Seedling Dry Weight:
The weight of seedling excluding the cotyledon is taken on 10th day after drying at 100 °C for 24 hr in grams. The lot exhibiting the maximum seedling dry weight is considered as vigorus.
4. Vigour Index:
A combination of standard germination test with seedling length provides broad evaluation of seedling vigour. Seed lot with high vigour index considered as vigours.
Vigour index-II = Germination X Seedling length on the day of final count.
5. Seed Metabolic Efficiency (SME):
The amount of dry seed weight that is respired for producing 1g of root and shoot is metabolic efficiency of the seed. Thus higher the value of SME, lower the efficiency of seed as more seed reserve would be used for producing root and shoot.
Amount of food material respired (RESP) is calculated as:
9. Experiment on Seed Vigour (Electrical Conductivity Test):
Objective:
Determination of seed vigour.
Principle:
The solute leaked out from seeds into the water is not available to the seed resulting in poor field emergence. Degradation changes in the cellular membrane causing increased permeability and leakiness. A deteriorate seed lot leaches more water soluble compounds than a vigorous one when soaked in water. The electrical conductance of a solution will be higher with the high concentration of ions in the solution.
Equipment and Chemicals:
Analytical balance, beaker, deionized water, incubator, electrical conductivity meter.
Procedure:
Three replications of 50 seeds from each lot are weighted to 2 decimal place in a beaker. 250 ml deionized water is added in each beaker. These beakers are kept at 20° C for 24 hours after proper covering to reduce the evaporation and contamination. A beaker containing deionized water with no seed is set with each test as control. After 24 hours the soak water is poured through a coarse sieve into another beaker to remove the seed.
The electrical conductivity of water is measured by electrical conductivity meter at constant temperature with shaking of beaker. The conductivity of water in control is subtracted from the reading of soak water before calculating the conductivity per gram of seed and expressed as micro siemens/g of seed (µs/cm/g).
10. Experiment on Seed Treatment:
Objective:
Improvement in shelf life of seed, protection of the seed during germination, seedling establishment and improvement in the vigour of seedling and plant with chemical or physical treatment.
The chemical may be a fungicide or antibiotic or nematode with different formulation including, water dispersible powder (WP), dust or slurries are used to control specific pathogen. Based on the mode of action the chemical may be a protectant i.e. the chemical that becomes effective when applied prior to infection e.g., captan, thiram, organo-mercurial, mancozeb, ziram, ferbam etc., and the therapeutant i.e., the chemical that is capable of eradicating the pathogen after it has caused infection and thereby cure the plant e.g., carbandazim (bavistan, derosol), oxathin (vitavax), benzidmiazole (benomyl) etc.
The chemicals those act by entering into the system of the plant are known as systemic e.g., therapeutant chemicals, whereas, the another chemicals, which do not act systemically are called non- systemic e.g., protectant chemicals.
Seed Treatment with Chemicals:
Seed can be treated with following methods:
1. Rotary Seed Dresser:
Small quantity of seed is treated by rotary seed dresser.
2. Slurry Treater:
Large quantity of seed in seed processing plant is treated by slurry treater. The required quantity of the chemicals is automatically mixed with the specified quantity of seed before bagging. In a seed processing plant it is a continuous process and is more efficient than rotary seed dresser.
3. Seed Dip Method:
It involves the dipping of seed or propagating material in a chemical (fungicide, antibiotic etc.) solution for a specified period prior to sowing. Seed soaking with organo-mercurial (for potato scab), mancozeb or mancozeb 64% + metalaxyl 8% (for potato late blight), streptomycin sulphate (for cabbage, cauliflower fungal diseases) have been found effective.
11. Experiment on Seed Priming:
Objective:
To describe the process of seed priming.
The benefits from priming treatments include increased germination, uniform emergence, germination under optimal and sub optimal environments and improved seedling vigor and growth.
Osmopriming (osmoconditioning) is the standard priming technique. Seeds are incubated in well aerated solutions with a low water potential, and afterwards washed and dried. The low water potential of the solutions can be achieved by adding osmotica like mannitol, polyethyleneglycol (PEG) or salts like KCl.
Hydropriming (drum priming) is achieved by continuous or successive addition of a limited amount of water to the seeds. A drum is used for this purpose and the water can also be applied by humid air. ‘On-farm steeping’ is the cheap and useful technique that is practized by incubating seeds (cereals, legumes) for a limited time in warm water.
Matrixpriming (matriconditioning) is the incubation of seeds in a solid, insoluble matrix (vermiculite, diatomaceous earth, cross-linked highly water- absorbent polymers) with a limited amount of water. This method confers a slow imbibition.
Influence of Seed Priming on Lettuce Seed Emergence:
Placed lettuce seeds in 250g PEG/1000 ml H2O for one week at 15°C temperature. A similar lot of lettuce seeds are not primed. The primed and unprimed seeds should be sown in one part sandy loam and one part peat moss in translucent plastic boxes 1 cm deep. The boxes are kept at a 12- hour photoperiod at 15°C for five days.
Record the per cent emergence on following table:
12. Experiment on Seed Pelleting:
Objective:
To describe the process of seed pelleting.
Seed pelleting is the process of enclosing a seed in to a small quantity of inert material just large enough to produce a globular unit of standard size to facilitate precision planting. The inert material creates natural water holding media and provides small amount of nutrients to young seedlings.
Equipments:
Pelleting machine, seeds, adhesive materials, pelleting materials, filler materials.
Process of Pelleting:
The three basic steps involved in pelleting are stated as stamping, coating and rolling. The materials need for pelleting seed are adhesive and filler materials. The seed are uniformly coated with adhesive in correct quantity initially. Then the filler materials are sprinkled on the coated seeds and are rolled on the filler material for effective and uniform coating.
13. Experiment on Seed Packaging:
Objective:
To maintain the seed quality for marketing and safe storage.
The choice of packaging materials and amount of seeds to be packed will depend on several factors such as the kind of seed to be packed, duration of storage, storage environment, seed moisture content, cost of packaging materials and geographical area where seeds will be stored.
Types of Packaging Materials:
i. Moisture-vapour permeable containers, e.g. jute bag, cloth bag, paper bag, multiwall paper bags etc.
ii. Moisture-vapour resistance containers e.g. jute bag laminated with thin (200- 300 gauge) polythene film.
iii. Moisture-vapour proof containers, e.g. tin cans, polythene bags of 700 gauge or more, aluminium foil pouches etc.
Commercially available polythenes are of 3 types, e.g. low, medium and high density. Density differences are due to differences in molecular structure, which determines the physical structure. Low density polythene is generally considered more satisfactory for seed storage.
i. Polythene deteriorates on direct exposure to sun light or ultraviolet radiation. Therefore it should be protected.
ii. If moisture-vapour proof containers are used for packaging vegetable seeds, moisture content must not exceed beyond a critical level which varies for different kinds of seeds.
14. Experiment on Seed Marketing:
Objective:
Have an understanding of the marketing systems & price for different kind of vegetable seeds.
Seed marketing is the process through which seed move from the farm where it is produced to the consumer who plants it. The marketing process may be as simple as farmers exchange of seed or it may be as complex as a transaction involving several middlemen and a highly organized seed industry.
i. Visit a retail and wholesale seed outlet in particular area.
ii. Invite seed sales representative to talk about his marketing program.
iii. Invite a representative from the seed certification program to discuss how certified seed is marketed.
