It has been a month i hadn't been so active at this platform due to my trainings and hectic assignments and internal examination and i would like to apologize with everyone.

Being an agriculture student i had ever tried to circulate some basic agriculture practices that everyone could practice. Everyone may have some fond of planting seed establishing garden at their house and sometimes we even dont have some information on the basic practice that can be followed with small budget. Today i had written something about the priming technology that has beneficial impact on the germination of the seed. 

Good crop establishment is one of the pressing challenges in the agricultural production. The major constraint for the proper crop abolishment includes poor seed bed preparation, use of low quality seeds, delay sowing, inadequate soil moisture, poor sowing techniques and various adverse abiotic conditions. Quality seed is the basic and most vital input for the crop production. Under the favorable environment condition, a viable seed can germinate except when it is in the state of dormancy. Rapid seed germination and crop establishment are most important  factor for crop production under stress condition apart  from physiological dormancy. Among various technique implemented to minimize germination related problem, seed priming is one of the most accepted cheap technique to improve seed germination as a result  of which add significant role in the proper crop establishment. Priming lowers the mean germination duration, seedling vigor index, and germination energy. A seed can be primed with water, organic salt, chemicals and hormones.

Seed priming (osmo conditioning, osmotic priming) is the process of controlled pre-sowing treatment of seeds that involves exposure of seeds to a minimum external water potential which lowers hydration as a result of which trigger the  normal metabolic processes during early stage of germination before radicle protrusion. The main objective of the seed priming is to hydrate partially seed on a point where the germination processes are started but not completed. Various report has suggested that primed seed emerges 12 hour earlier than non-primed seeds which may be due to increased metabolic and biochemical activity of amylase, protease and lipase, improved antioxidant defense system, protein synthesis which act a significant role in breaking down of macromolecules for proper growth and development of embryo which results in synchronized and resistant seedling emergence. There are still various physical and chemical factors influencing priming success such as osmotica and water potential, priming agent, duration, temperature, presence or absence of light, aeration and condition of seeds. The mechanism of germination of seed after priming implies the three phases: (1) Phase I: Imbibition of the dry tissue related to water movement occurs in apoplastic spaces; (2) Phase II: activation of the metabolic activities in the cell level; (3) Phase III: initiation of growing process i.e the cell elongation and protrusion of radicle. Priming strategies not only improves the rate and uniformity of germination but also improves behavior of seedling in terms of plant growth and stress resistance.

Priming techniques has multihued importance not only in the proper crop establishment through synchronous germination but also assists seed bank operators who requires improved protocols of ex-situ conservation of  germplasm collection. There are various priming technology adapted by farmers to maintain uniform crop establishment, enhance crop yield and maintain resistance towards adverse environmental stress. The most commonly followed are hydro priming, osmo priming, halo priming, solid matrix priming and bio priming.

(A) Hydro priming: Hydro priming is the methods in which the germination is initiated  through the imbibition of seed with water for a limited time period (7-14h) without the emergence of the radicle. This technique has been used to speed up uniformity of the germination process improving the final stand of crop. This technique constitute phase II metabolism without contributing any stress level on seed grain. The emergence of radicle i.e phase III is prevented by drying the grains to their original moisture content. This is the most environmentally friendly, low cost technology with a great success under both optimal and stress condition. In order to ensure desirable level of seed hydration and protect radicle protrusion it is crucial to maintain accurate treatment duration, temperature and water volume. The major limitation of this technique is the inaccurate application of different factor leads to the lack of metabolic activation in seed followed by unsynchronized emergence of seedling.

(B) Osmo priming: It is the process which involves the soaking of seeds in osmotic solution with relatively  low water potential instead of water for a time period of 12-48 hours in the absence of light. The major compounds used for the osmopriming techniques includes polyethylene glycol (PEG), mannitol, glycerol, sorbitol and inorganic salts like NaCl, KCl, Potassium phosphate, calcium chloride etc. Because of the low water potential of the osmotic solutions, the permeability of water is enhanced as a result of which allows gradual seed imbibition and activation of seed germination preventing protrusion of radicle. Among the above mentioned chemicals, PEG is widely employed for osmo priming due to the fact that it constitute some specific characteristics such as high viscosity, large molecular size which prevents its penetration inside seeds eliminating the induction of cytotoxic effect along with minimizing of  osmotic potential within seed. Under unfavorable condition of chilling, water and salinity stress seed priming with PEG has been proven as an effective process to enhance seed germination, seedling emergence and stress tolerance of  various crop plants.

(C)  Bio priming: This method involves combined seed imbibition and bacterial inoculation  of seed which on one hand enhances rate and uniformity of seed and on other hand prevents seeds against soil and seed borne pathogens and infections. Seed priming of pathogen infested seed can lead to enormous growth of microbial organisms hindering overall plant health. So in order to prevent this, application of antagonistic microorganisms during priming will be an ecological approaches to overcome this problem. Some microorganisms such as rhizobacteria, pseudomonas are widely used for bio priming. Thus use of bio priming techniques with plant growth promoting bacteria(PGPB) seems to the promising approach for agricultural practices.

(D) )Solid matrix priming: Due to the high cost of osmotic agents and technical constraints with aeration, Solid matrix priming has been developed as an alternatives to osmo priming  where water uptake of seed is controlled by mixing seed and incubating seed with wet carrier for limited time interval. Then the seeds are separated from matrix, rinsed and back dried. Using of solid materials facilitates seeds to hydrate slowly and resemble natural imbibition process occurring in soil. The substances that are used during this process are Vermiculite, peat moss, charcoal, sand, clay etc . Use of sand is most economical and sand priming assists in enhancing performance of antioxidant enzyme such as catalase (CAT), peroxidase (POX) by improving germination rate under high salt stress conditions.

(E)  Others method: Chemical priming are also used in some of the commercial farms that includes the priming with natural and synthetic compounds such as antioxidants like ascorbic acids, melatonin, proline, thiourea, mannose, selenium, chitosan. Fungicides etc. Nutripriming is also an emerging methods which aims to obtain nutritional effect along with biochemical advantages of priming to improve germination parameters, seedling development. Similarly hormopriming of seed has also been developed where the seed imbibition occurs in the presence of plant growth regulators such abscisic acid, auxins, gibberellins, ethylene which has direct impact on seed metabolisms, photosynthetic rate and antioxidant system.

To sum up, seed priming is an effective emerging techniques for the qualitative and quantitative crop yield. Among the various technique and methods of priming hydro priming has been proven as an affordable, economical and promising method for the farmers to ensure uniform germination, seedling emergence and crop production.