Green gram is a protein-rich pulse. It is an annual crop, sensitive to changes in the environment: salinity and water deficit affect growth, development, and yield.
Priming, by pre-soaking the seeds, in specific chemicals, is often found to aid uniform seed germination and improve tolerance towards abiotic stress. Having explored many chemical seed priming methods in their laboratory, K. C. Jisha and Jos T. Puthur from the University of Calicut went on to investigate the effect of hydropriming green gram seeds – soaking seeds in water before subjecting them to osmotic stress.
The team obtained green gram seed varieties from the Seed Science and Technology division, ICAR, New Delhi. These varieties differ in their drought and salt tolerance. PusaRatna is stress-sensitive, Pusa 9531 drought-tolerant and Pusa Vishal, salt-tolerant.
The team soaked the seeds in distilled water for 6 hours for hydropriming. After air-drying, they germinated primed and non-primed seeds in plastic bottles with absorbent cotton soaked in varying amounts of salt or polyethylene glycol to mimic osmotic stress.
They monitored germination and found that a salt concentration of 75 mM and a 15% polyethylene glycol solution reduced growth in the stress sensitive PusaRatna by 50%. The stress tolerant varieties, on the other hand, showed growth reduction only when salt levels reached 100 mM .
On the seventh day of germination, they analysed the plants biochemically. And found that hydropriming resulted in increase in chlorophyll content in all three varieties.
The stress tolerant varieties showed increase in proline content – an indicator of the capability to manage stress.
Interestingly, all the primed seeds showed a decrease in malondialdehyde, an indicator of lipid injury by reactive oxygen species generated by environmental stress. This suggests the protective role played by seed hydropriming against oxidative stress.
PusaRatna and Pusa 9531 showed increased levels of the superoxide dismutase enzyme and the Pusa Vishal variety showed increase in peroxidase, showing that hydropriming improves antioxidant enzyme activity.
Environmental stresses impact food production and threaten food security. Existing industrial methods use synthetic compounds for priming seeds. The methodology proposed by Jisha and Jos is simple and cost-effective. And it is a method that could be used by farmers to improve green gram yield, especially in rain fed areas.
Ref: Agri Res, 7: 145-151 (2018), DOI: 10.1007/s40003-018-0306-x
Srividya K V, Freelance Science Writer, Thrissur