The study was recently published in U.S. journals
A team of researchers at the Indian Institute of Science Education and Research (IISER), Bhopal, has conducted a study on seed germination that could have a major impact on agriculture in the long run by helping determine the optimum timing of seed germination and thus ensure high plant yields.
The work carried out by Premachandran Yadukrishnan, P. Valappil Rahul and Nevedha Ravindran under the guidance of Sourav Datta, associate professor at the department of biological sciences at IISER, focused on the interplay between plant hormones like abscisic acid (ABA) which inhibit the sprouting of the seed and environmental cues like light (which promotes the sprouting process) and darkness.
Their findings were recently published in two U.S.-based publications: The Plant Journal and Plant Physiology.
Although ABA, a ubiquitous plant hormone, was discovered almost 80 years ago and the mechanisms underlying germination inhibition by this protein have been the subject of intensive research, there is scant knowledge about the mechanisms controlled by ABA for arresting the post-germination growth in response to environmental cues. This is the gap that the IISER team has attempted to bridge with its experiments.
“All plants, depending on their external environment, make the decision to open its embryonic leaves after sprouting or to enforce a growth arrest. Being ‘sessile’ [fixed to a place], plants have an extraordinary sensing mechanism to allow them assess environmental conditions before a seed decides to open up and establish as a young seedling. Like humans, plants, too, have hormones like ABA that modulate their growth and development,” Mr. Datta said, adding that just like humans were forced to mediate a COVID-19-induced lockdown, plants, too mediate a “developmental lockdown” under stressful conditions to ensure their survival.
He said that just after sprouting, the young seed must take a crucial decision on whether to go ahead with the ‘seedling establishment’ process (the critical stage of plant growth) or not.
The ‘right decision’ taken by the young seed ultimately allows it to secure its independence and take care of itself as it matures into an adult plant.
“It is analogous to the baby steps in humans before a child can stand on its own feet and walk. Making the right decision in the allocation of resources to growth or stress responses is critical for the successful establishment of seedlings. If seeds germinate in adverse environmental conditions, seedlings ultimately risk expediting precious energy in ‘stress defence’ rather than growth,” Mr. Datta said.
Mr. Datta said understanding the complex factors that modulate ABA sensitivity is vital to developing economically important plant varieties that have better tolerance to stress conditions.
The results of the study, though in its elementary phase, are vital as they come at a time when frustrated farmers across Maharashtra have lodged thousands of complaints against seed companies, alleging them of having provided them with seeds that failed to germinate.
Over the past two months, more than one lakh farmers in Maharashtra have lodged complaints against seed companies, prompting the State Agriculture department to lodge over 75 FIRs against seed companies for giving soybean seeds to farmers which failed to germinate.
Explaining the critical role of ABA, Mr. Yadukrishnan said the protein acts as a ‘master regulator’ of the seed’s growth by controlling several aspects of plant development, including seed dormancy and germination, as well as controlling growth under adverse conditions such as drought or salinity.
“Considering that survival in such conditions can be really challenging, the ABA signals the seed not to germinate until there are favourable conditions for growth. If the stress comes after the germination of a seed, ABA suppresses further growth of the seedling. This inhibition leads the seedling to invest its energies less in its growth and more in ‘defence mechanisms’ designed to ensure its survival,” he said.
Mr. Yadukrishnan said that their research proved that the inhibition of seedling growth by ABA is much stronger in darkness as compared to light conditions.
“We found that COP1, a protein that is more active in dark and less active in light, is responsible for this relatively higher ABA sensitivity in dark conditions. Our work provides mechanistic details about the role of COP1 in integrating light and ABA signals to coordinate the post-germination growth arrest,” he said.
Mr. Datta said that COP1, which is a highly conserved protein (protein which undergoes fewer amino acid replacements), may play similar roles in different crop plants.
“However, as COP1 plays multiple roles in plants, we need more details of other proteins associated with it specifically in this process. We are currently working to find these additional factors which might enable using this as a strategy for crop improvement programmes in the future,” he said.
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