Salinity modulates morpho-physiology, biochemical and antioxidant defence system in Tetragonia decumbens Mill.: a neglected wild leafy vegetable in South Africa

Abstract

Tetragonia decumbens is an edible halophyte that grows naturally in saline environment; however, its tolerance mechanisms are poorly understood for bio-saline agriculture. So, this research was designed to look into how salinity affects vegetative growth, leaf succulence, chlorophyll content, cation accumulation, oxidative stress indicators, and antioxidative defence mechanisms involved in the salt tolerance of T. decumbens. Saline conditions were prepared by dissolving sodium chlorine (NaCl) in the nutritive solution. The control was maintained and only watered with nutrient solution while the tested treatments contained graded NaCl doses (250, 200, 150, 100, and 50 mM). Results revealed a substantial enhancement in shoot length, number of branches, relative water content, as well as total fresh weight in plants irrigated with 50 and 100 mM NaCl in comparison to the control, while higher saline concentrations (150–250 mM NaCl) reduced plant growth and chlorophyll content. Similarly, these high salt concentrations induced more severe oxidative stress indicated by high amounts of superoxide, cell death viability and malondialdehyde, with the most pronounced effect at the highest NaCl concentration (250 mM). Nevertheless, T. decumbens modulated various defence mechanisms with increasing salinity stress, these include the upregulation of superoxide dismutase, catalase, polyphenols, flavonoids, proanthocyanidins and the build-up of sodium ions in the leaves. These results show that T. decumbens can withstand salinity by modifying its morpho-physiological traits, antioxidant defence systems, and managing ion toxicity and oxidative stress efficiently, since all plants withstand salinity without showing signs of toxicity.