Salinity influenced growth, physio-biochemical responses, and antioxidative potential of Trachyandra ciliata Kunth (wild cabbage)

Abstract

Trachyandra ciliata is a wild edible halophyte endemic to the saline Western Cape coastal region. However, its tolerance mechanisms and physio-biochemical responses under salinity stress are undocumented. Thus, this study was conducted to evaluate the effect of salinity stress on growth parameters, leaf hydration, photosynthetic pigmentation, oxidative stress markers and concentration of antioxidative enzymes to further understand mechanisms involved in its salt tolerance. Four salinity concentrations (50, 100, 150, and 200 mM) were assessed by adding NaCl into the nutrient solution, while control was solely irrigated with nutrient solution. The results revealed that salinity positively influenced growth parameters in all plant parts at low concentration (50 mM NaCl) compared to the control. Moreover, the total chlorophyll content negatively correlated with increasing salinity. Trachyandra ciliata maintained equivalent relative water content (RWC) from control to 100 mM treatment, which then efficiently decreased with increasing salinity, while leaf succulence was equivalent among all treatments. On the other hand, high salinity stimulated oxidative stress as indicated by high MDA, cell death, and superoxide radicals, which were more expressive under 200 mM treatment. To counter the catastrophic effects of excessive ROS, T. ciliata activated antioxidative defence mechanisms as indicated by high SOD and CAT antioxidative enzymes which were more prevalent at high salinity (200 mM). Furthermore, the high proline content under higher salinity treatments ensured further scavenging of ROS. These findings validate that T. ciliata is able to tolerate salinity by modulating bio-physiological processes to manage oxidative stress and achieve cellular homeostasis under salinity stress.