Also known as seed invigoration, seed enhancements are post-harvest treatments to improve the growth as well as germination of seedlings at the time of sowing. According to i49, a noted seed bank, the most commonly used seed enhancement techniques include enhancement using physical agents, physiological enhancements, biological enhancements, and seed coating and pelleting.
Physical Agents for Seed Enhancement: Seeds undergo physical treatments without the application of any chemicals or hydration of the seeds. The objective is to improve germination and the establishment of the seedling. The exact mechanism of the invigoration of seeds using physical techniques in still not clear. Numerous studies have been conducted in recent years on seed invigoration using plasma technology for horticultural and agronomic crops. Out of all physical methods, magnetic field and irradiation with ionizing radiations or microwaves is considered to be extremely promising for pre-sowing seed treatments.
- Magnetic Field Treatment: Magnetic seed stimulation involves affecting germination, growth of the seedling, and subsequent crop yield by identifying the magnetic exposure dose. Exposure to a magnetic field not only improves the non-standard seeds’ germination but also improves their quality.
- Plasma Treatment: Plasma application is a relatively recent application in the field of agriculture. Numerous studies suggest that the use of plasmas along with gases such as helium, cyclohexane, and aniline can affect a seed’s mechanism of germination and growth enhancement. Plasma treatment improves plant growth and seed quality while helping attain zero seed destruction.
- Radiation Treatment: Recent advances in agriculture suggest that gamma rays can be used to improve plant characteristics such as grain yield, salinity tolerance, product quality, precocity, etc. Gamma radiation can also prevent pathogen infestation by sterilizing agricultural products.
Physiological Seed Enhancement: Physiological enhancement of seeds primarily refers to the technique of seed priming. This pre-sowing approach is intended to influence the development of seedling by the stimulation of pre-germination metabolic activities. A controlled hydration process, seed priming involves dipping seeds in water or any other solution for a specific period of time so that the metabolic activities can be completed by the seed before its sowing. These treatments include osmopriming, hydropriming, hormonal priming, and nutrient priming.
- Hydropriming: This refers to a process of controlled hydration where the seed is soaked in plain water and is re-dried. This technique requires no chemicals and is considered to be a suitable treatment under drought-prone environments and salinity stress.
- Osmopriming: This technique involves using an osmotic solution for seed hydration. Polyethylene glycol solution is most frequently used in osmopriming to check radicle protrusion and regulate water uptake. The most commonly used salts include potassium nitrate, potassium chloride, magnesium sulfate, sodium chloride, etc.
- Hormonal Priming: Different plant growth hormones, as well as their derivatives, can play a significant role in all phases of plant development including seed germination. Many crop species have experienced better germination, growth, and yield with the help of cytokinin priming. Gibberellic acid priming can help speed up germination by stimulating the hydrolytic enzymes.
- Nutrient Priming: It is possible to improve the growth and yield of several crops by applying micronutrients with priming. Nutrient priming has been experimentally proven to be capable of improving rice, wheat, and forage legumes. Seed treatments for field crops extensively make us of micronutrients such as B, Zn, Mn, Mo, Co and Cu.
Biological Seed Enhancement: This is done primarily in two ways.
- Bacterial Seed Agents: In this technique, soil-borne, free-living bacteria species commonly known as PGPR or plant-growth-promoting rhizobacteria are applied to roots, seeds, and soil to promote plant growth and reduce diseases.
- Fungal Seed Agents: Biopriming of seeds can also be done using several bacterial and fungal agents that help improve growth and yield while eliminating biotic as well as abiotic stress factors.
Coating and Pelleting: Seed film pelleting, coating, inoculation, and priming are now extensively used techniques for enhancing the storage, germination, distribution, and plantability of seeds. Adhesive films, herbicides, fungicides, biological agents and growth promoters are added to the seeds in this technique.