Morpho-physiological and biochemical tolerance mechanisms in two varieties of Oryza sativa to salinity

Abstract

One of the major detrimental factors of the global rice production is salt stress, which limits it up to 50 percent. In this study, we compared the morphophysiological and biochemical responses of indigenous salt-tolerant 'Korgut' and salt-sensitive 'Jaya' rice (Oryza sativa L.) varieties by pot culture in controlled climatic conditions. Decreased plant growth and biomass with the increase in salinity were recorded in the 'Jaya' variety compared to those of 'Korgut'. Net photosynthesis rate (P sub(N)), transpiration rate (E), stomatal conductance (g sub(s)), internal CO sub(2) concentration (C sub(i)), photochemical quenching, and lower quantum efficiency of PSII system (F sub(v)/F sub(m) ratio) were recorded reduced in 'Jaya' compared to those of 'Korgut' as response to salinity stress. Unlike 'Korgut' that thrived well under increased salinity levels, higher concentration (160 mmol/L) of NaCl caused a decrease in the number of thylakoids. In addition, swelling of the thylakoids was observed in 'Jaya' in response to higher salt stress. The tolerance of 'Korgut' plants was mainly due to relatively lesser accumulation of Na sup(+) and Cl sup(-) and higher accumulation of K sup(+). 'Korgut' showed relatively higher antioxidant capacity, lower osmotic stress (proline), and oxidative damage (lipid peroxidation) compared to salt-sensitive variety 'Jaya'. Our data suggests that 'Korgut' plants preserve ion and water homeostasis and diminish oxidative stress resulting from more significant antioxidant enzymes, which enables better sustainable growth overcoming salinity stress, contrary to salt-sensitive 'Jaya' variety. These findings can support crop development in terms of salt tolerance in rice crops by the method of molecular genetics.