Melatonin is a low molecular weight hormone found in mammals and a natural bio-stimulating molecule in all living organisms from prokaryotes to eukaryotes. In plants melatonin plays an important role as a growth regulator and a stress buffering agent but its role under heat stress in rice reproductive stage remains undetermined. In the present study we have identified melatonin’s role to alleviate heat stress mediated damages to photosynthesis system and chlorophyll damage in two contrasting genotypes for heat stress tolerance. High temperature stress was given at anthesis and the treatment of melatonin was applied as foliar spray. We observed that melatonin treatment significantly increased chlorophyll content under heat stress compared to mock treated plants. Further, our studies on photosynthetic traits gave an insight to melatonin mediated improvements on photosynthesis rate across all the treatments but more significantly in the thermo-sensitive genotype. Improved photosynthesis rate and chlorophyll content might be due to direct antioxidant scavenging and improved antioxidative system. All these findings show that melatonin has a potential role to develop crop varieties with higher stress tolerance capacity.
The present study was carried out during rabi 2017-18 at ICAR-Indian Agricultural Research Institute, New Delhi to investigate the effect of stay-green trait on grain yield in wheat under combined heat and drought stress. Two high stay green (GCP 6 and GCP 33) and two low stay green (GCP 23 and GCP 30) Recombinant Inbred Lines (RILs) of wheat along with their parents (HI1500/DBW43) were grown in field conditions under timely sown with irrigation (control) and without irrigation (drought stress), and late sown with irrigation (heat stress) and without irrigation (combined heat and drought stress). High stay-green RILs showed the reduced levels of abscisic acid and ethylene production during anthesis stage under heat, drought and combined stress conditions as compared to low stay green RILs. Furthermore, there was significantly better yield was observed in high stay-green RILs as compared to low stay-green RILs. Thus our study concludes that stay-green traits improve the yield in wheat under combined heat and drought stress condition by delaying the senescence through reduced levels of abscisic acid and ethylene.
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