Evaluation of heat stress induced plant metabolites in Fagopyrum esculentum Moench. by exogenous application of plant growth promoters

Global warming has a direct relation with high temperature and management of heat stress in field crops is important for sustainable agriculture. Common buckwheat ( Fagorpyrum esculentum Moench.) is an emerging pseudocereal and alternative food crop but shows sensitivity to heat stress. This two years (2017 and 2018) research was conducted to explore the physiological and biochemical mechanism of improving heat stress tolerance in buckwheat with foliar spray of different plant growth promoters (PGPs). The preoptimized levels of moringa leaf extract (MLE) of fresh (MFLE, 3%) and dried leaves (MDLE, 10%), ascorbic acid (AsA, 0.5 mM), a vitamin biosynthesized in plants and thiourea (TU, 10 mM), a synthetic growth bioregulator were foliar sprayed. Results revealed that growth attributes including shoot (34.61%) and root length (27.62%), dry weight (641.94% and 40.23%, respectively), stem diameter (52.05%), no. of roots per plant (27.27%), leaf area (24.86%), and no. of internodes per plant (16.17%) were impaired by heat stress. Similarly, antioxidants including leaf and root superoxide dismutase (17.11% and 21.43%), peroxidase (16.81% and 8.40%) and catalase (6.51% and 6.54%), respectively, were significantly affected by heat stress. PGPs spray alleviated heat damage by reducing the biosynthesis of leaf and root MDA and H 2 O 2 , and preferential induction of enzymatic antioxidants. PCA-biplot analysis showed that, amongst PGPs, MDLE was greatly effective in inducing antioxidant defense under heat stress. PCA and correlation matrix revealed that PGPs prompted induction of antioxidants was effective more in roots than leaves under heat stress. Conclusively, the induction of antioxidant defense with the PGPs especially with MLEs spray is the main mechanism, with great implications for heat tolerance in common buckwheat.