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| Seed treatments for maximizing productivity | | | Ravneet Kour, R.K. Samnotra and Rakesh Kumar | 12/15/2015 12:10:45 AM |
| Seed is the the pre-requisite in any production programmme. Various seed treatments like seed fortification, seed hardening seed infusion, seed osmopriming and seed pelleting improve seed vigour, germination, storability, seed performance in the field and consequently the production and productivity.
Seed fortification :- Seeds fortification is a process of enriching the seeds with bioactive chemicals for improving germination and seeding vigour and to overcome dormancy (Khan 1977). It involves impregnation of required substance for improved production where seeds are soaked either in water or dilute solution of bioactive chemicals such as micronutrients, growth regulators, vitamins and seed protectants. The seed vigour is the sum total of all seeds attributes that favour stand establishment under varying field conditions whereas the seed invigouration is an improvement in seed performance by any post harvest treatment which results in improved germinability, greater storability and better field performance than the corresponding untreated control. There are various treatments which help to improve the seed viguor and consequently the the production.
Reason for seed fortification :
o To improve seed and seeding vigour
o To improve germination of seeds
o To improve storability of seeds
o To overcome dormancy
Process of seed fortification:- One third volume of nutrients solution is added to the known volume of seeds and allowed to imbibe for short duration .The imbibed seeds should be dried under shade. If immediate sowing is planned, drying back to original moisture content is not important otherwise seeds should be dried back to original moisture content.
How it helps? :- Seeds fortification helps to improve germination and seed vigour due to supplemental nutrients provided. Secondly, the use of bioactive chemicals used for fortification may help to overcome the dormancy . Thirdly, the use of ferrous sulphate helps in increasing seed storability by bringing about significant reduction in lipid peroxidation & therefore, increases the life of seed.
Method of seed fortification:- Seeds are soaked in solution for duration of 6-24 hrs depending upon the crop to raise the moisture content of the seed to 20-25% just enough for endogenous impregnation of chemicals by exogenous application. The choice of chemicals, its concentration and duration of soaking time may vary from species to species is a major factor for success of treatment.
Chemicals used for seed fortification :- The macro and micronutrients are used for fortification as they are essential for physiological activation of seeds.
Nitrogen :- It is a constituent of aminoacids, nucleotides and also act as coenzyme.
Phosphorus:-Constituent of phospholipids, nucleotides and also sugar phosphates.
Potassium:- Required by all higher plants for action of enzymatic process .
Sulphur :- Constituent of amino acids like cysteine, methionine and cystenine.
Magnesium:- Constituent of chlorophyll. It is an activator of enzymes and their metabolism and MgSO4 and MgCl2 are widely used Mg forms.
Boron:- Boron markedly affects nitrogen uptake and metabolism of nitrogen compounds.
Molybdenum:-It is essential for utilization of nitrate and boron. It reduces the nitrate to ammonium and helps in formation of amino acid. It also helps in fixation of nitrogen.
Zinc:- Zinc acts as an activator of several enzymes, alcoholic dehydrogenase, pyridine nucleotide dehydrogenase and carbonic anhydrase. It may also act as an activator for some phosphate transferring enzyme such as hexokinase or triose phosphate dehydranase. It plays an important role in protein synthesis.
Precautions during seed fortification :-The volume of solutions used should be just enough so that all the seed are imbibed .Excess of water if used may lead to reverse osmosis and cause loss of essential nutrients contained in the seed. Leakage of solutes from seeds under treatment must be prevented. It can be also be prevented by the required concentration of chemicals should be used.
Seed infusion:- It is a method of impregnation of seeds with bioactive chemicals through organic solvents instead of water. It is suitable for seeds which suffer with soaking and seed coat injury. It also provides protective, regulatory and selective functions of chemicals to improve performance of seed.
Methodology:- Desired solutes are dissolved in organic solvent at desired concentration. Seeds are immersed in solvent for 4-24 hours depending upon species. After desired period the solvent is evaporated by air or vacuum desiccators for 30 minutes to 1 hour or under ambient conditions for 24 hours for complete expiry of solvent from seed. Then seeds are taken for sowing. The amount of chemical penetrated in to seed vary with;
Duration of treatment; Increase in duration treatment will increase the absorption of solutes.
Concentration of solutes; More the concentration of solutes, more will be the penetration.
Type of chemicals:- Compared to IAA, GA3 reaches the embryo lesser in quantity in a given time due to higher molecular weight.
Biochemicals used for seed infusion are :- Seed protectants like fungicides, bacteriocides, herbicide antidotes, growth regulators like GA3, IAA, Kinetin, macro and micronutrients and substances to resist stress conditions like fusicoccin.
Organic solvents used for infusion:-Acetone, Petroleum ether, Dichloro methane, Ethenol, Dichloro ethane.
Seed hardening:- Pre-sowing hardening is one of the best methods that results in modifying the physiological and biochemical nature of seed so as to get the characters that are favourable for drought resistance. Pre-sowing hardening is the result of extensive physiological reorganization induced by dehydration process. It can be done with water / dilute chemical solutions / growth regulating compounds or using commonly available natural tonics like coconut water or milk. The botanicals like Prosopis juliflora leaf extract (1%) can also be used for hardening purpose.
Methodology:-Seeds are soaked in required quantity of H2O depending upon crop seeds and allowed to absorb moisture upto 35% of their weight and spread out in thin layer for drying in shade for 2-3 days .during this time the seeds are dried to original weight.
Chemicals used for hardening:-Aqueous solution of salts like NaCl, NaSO4, KCl, KNO3, K2SO4, CaCl2, NH4SO2, ZnSO4
Growth promoters:- GA3, Chloro-choline chloride, Kinetin, Ascorbic acid, Succinic acid and 2-chloro ethyl phosphonic acid.
Vitamins; Vitamin K, Nicotinic acid, Pantothenic acid and adenine.
Plant products; :- Garlic extract, coconut water, Prosopis julifera, Albizia amara
Osmoticants:- D-Mannitol, Polyethylene glycol
Osmotic Priming:- Seeds are conditioned to face adverse conditions in the field when it is sown. Osmotic priming is very expensive but required process for large seeded legumes like peas and beans. They have high protein and large embryo and susceptible to soaking injury. High protein seeds are hygroscopic and hydrophilic. Osmotic conditions begin when seed is hydrated in low water potential osmotic solution. After moisture equilibrium is achieved, further uptake of water is prevented. It can be achieved by adjusting concentration of osmoticum in conditioning solution to a level just preventing germination.
Chemicals used for osmotic priming
PEG 6000:- High mol. compound, act as coating material, absorbs H2O and release ½ of its water potential to seed.
Mannitol:-Low molecular compound and highly toxic.
Others:- NaCl, KH2PO4, Glycerol, KNO3, MgSO4
Methodology:- Large seeds are soaked in 20-30% PEG 6000 solution and incubated at 15-200C for 7-21 days, washed with distilled water and air dried at 250C .Then osmoprimed seeds are sown.
Seed pelleting:- Seed pelleting is the process of adding inert materials to seeds to change their size and shape for improved plantability. Small and irregularly shaped seeds, such as lettuce seeds, can be treated as larger, round-shaped seed . Pelleting simplifies singulating seeds in the field and planting them in precise locations. For crops like onion, precise seed placement is of great advantage as uniform bulb development is assured with equal distance planting.
Benefits:- Over the years, the benefits of pelleting have grown to include:
o Increased oxygen penetration/availability
o Wider pellet density range allowing more accurate spacing of seed in a wide range of planting conditions
o Pellet loading
o Better field visibility
What kind of seeds are pelleted? Seeds of various sizes are commercially pelleted, from relatively large seeds like onion and tomato to very small seeds like lettuce species. For onion, the seed can increase in weight 6-fold due to pelleting.
Pelleted seed ingredients:- There are two components to a seed pellet: bulking (or coating) material and binder. The bulking material can be either a mixture of several different mineral and/or organic substances or a single component. The coating material changes the size, shape, and weight of the seed. Good coating materials allow for uniformity of particle size distribution while lacking any phytotoxicity. Different coating materials for pelleting are as follows;
Coating materials:- Lime, Gypsum, dolomite, rock phosphate and charcoal
Organic materials:- Dried blood, milk powder and yeast extract
Inoculants type of coating:- Rhizobium, Arbuscular Mycorrhizal fungi, Bacillus and Streptomyces.
Protecting coating:-Fungicides, pesticides, rodenticides, methiocarb and endrin (to prevent bird attack) .
Herbicide coating:- Antidote (108 prapthetic anhydride) and absorbent (2,4-D and alachlor).
Nutrient coating:- Seeds coated with macronutrients such as N,P,K and S and micronutrients such as Mo, Mg, Zn and Mn. It increases germination and seedling growth.
Hydrophilic coating:- Use of starch graft polymers can absorb H2O upto 1000 times of their original weight of water. Coating of MgCO3 increases movement of air and water. Coating of peroxides of Zn and Ca increase O2 supply to make the germination fast.
The second component, the binder, holds the coating material together. Binder concentration is critical because too much binder will delay germination. Too little binder will cause chipping and cracking of pellets in the planter box which can cause skips and/or wide gaps in the plant rows. Many different compounds have been used as binders, including various starches, sugars, gum arabic, clay, cellulose, vinyl polymers, and water. All pellets have the same volume; only the weight, and thus the density, of the pellet is different.
Seed treatments hold a promise in increasing the quality of seed and maximizing the productivity especially the seed pelleting technique is highly useful for active growth .Similarly the seed hardening and seed infusion are good under drought conditions.
Ravneet kour, R.K. Samnotra and Rakesh kumar
Division of Vegetable Science and Floriculture, SKUAST-Jammu |
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