Biostimulant priming in Oryza sativa: a novel approach to reprogram the functional biology under nutrient-deficient soil

Abstract

Biostimulants can be used as an alternative to fertilizers to overcome the effect of nutrient deficiency in plants. Yeast is a biostimulant, having the capacity to modify physiological processes in plants by improving germination and seedling growth under environmental stress. The effects of yeast extract, a sustainable biostimulant derived from yeast (Saccharomyces cerevisiae) containing all the nutritive values, amino acids, vitamins, and growth factors, were investigated in rice (Oryza sativa). Various growth parameters, Chlorophyll a fluorescence, PS II, metabolites accumulation, and antioxidative function of enzymatic (SOD, CAT, APX, GPOX) as well as non-enzymatic (phenol, AsA, and GSH) antioxidant were analyzed in two rice varieties (Hraswa-tolerant and Manu ratna-sensitive) in both yeast extract primed and non-primed seeds subjected to nutrient-deficient soil conditions. The application of the biostimulant (yeast extract) as a priming agent increased the biomass, photosynthetic pigment, modified chlorophyll a fluorescence-related parameters, and also enhanced the photosystem activities of seedlings, supported by decreased content of ROS and MDA in primed seeds when compared to non-primed ones. These changes were accompanied by a significant enhancement in osmolytes and non-enzymatic antioxidants (AsA, GSH, and total phenolics). In general, yeast priming under nutrient-deficient conditions appeared to stimulate the activities of SOD, CAT, and APX in var. Hraswa while GPOX was dramatically upregulated in var. Manu ratna. Thus, these results speculate that yeast priming under nutrient-deficient conditions maintained cell homeostasis and provided better adaptation to the stress conditions in both tolerant as well as sensitive varieties of rice seedlings.