The investigation of salt stress reducing the effects of some antioxidants in beans

In this study, the mitigating effects of antioxidants on salt stress in common beans (Phaseolus vulgaris) cultivation were investigated in growth chamber. Two different bean cultivars, salt-tolerant (BN150) and salt-sensitive (BN16), were used. Initially, 25 mM NaCl concentration was applied, followed by a final concentration of 35 mM NaCl to induce salt stress. Antioxidants such as 100 mM glycine betaine, 100 µM jasmonic acid, 100 µM nitric oxide, 100µM melatonin, 0.5 mM salicylic acid, and 200 ppm potassium silicate were utilized. It was determined that the antioxidants applied to the bean plants mitigated the effects of salt stress on physiological parameters such as stomatal conductance, membrane damage, relative leaf water content and leaf water potential in plant leaf tissues. The antioxidant concentration significantly increased chlorophyll a, chlorophyll b, and total chlorophyll content under salt stress. Salt stress increases ROS(Reactive oxygen species) levels, leading to lipid peroxidation and initiating a chain reaction that destroys lipids and forms lipid radicals, resulting in the production of malondialdehyde (MDA), considered a significant biomarker of oxidative stress. Antioxidants significantly reduced the MDA production. The antioxidants increased the activities of phenols, flavonoids, proline, ascorbate peroxidase (APX), and glutathione reductase (GR), forming an antioxidative defense system in plant tissues under salt stress, thereby reducing oxidative damage. Antioxidants improve the plant growth traits such as plant height, plant fresh weight, number of leaves, and stem diameter. Similiarly, antioxidants considerably enhanced the concentrations of both macro-nutrients (N, P, K, Ca, Mg) and micro-nutrients (Zn, Cu, Fe) in the leaves under salt stress. Furthermore, the concentrations of Na and Cl were found higher in salt stress conditions which were decreased with antioxidant applications. It was concluded that antioxidant applications have positive effects on plant growth parameters, physiological parameters, and antioxidant activities in common beans grown under salt stress.