High tolerance and adaptive responses to salinity of a valuable medicinal plant Grangea maderaspatana

Abstract Grangea maderaspatana is a valuable medicinal plant growing in salt-affected areas, but its tolerance capability, physiological and biochemical responses to salinity is still unclear. To understand these traits, this study examined effects of salinity at different levels (50-400 mM NaCl) on plant growth and its responses. The results shown that the plant’s dry biomass decreased with increasing salinity levels of 100-400 mM NaCl, but its growth was maintained at 400 mM NaCl level with a dry biomass equal to 0.45 times that of the control, indicating that G. maderaspatana had a tolerance ability to high salinity. The plant also had adaptive responses to the salinity. The content of leaf chlorophylls and carotenoids were retained, even enhanced by 50-200 mM NaCl, suggesting a high adaptation of photosynthesis. Proline, Na+, and Cl- was highly accumulated while the accumulation of K+ and NO3 - was maintained with 200-400 mM NaCl, indicating that the plant had adaptive mechanisms for osmotic adjustment and ion homeostasis. Antioxidative activities of catalase, superoxide dismutase, and peroxidase were enhanced by the salinity. These findings are useful information for understanding salt tolerance mechanisms and for utilization of this medicinal plant in saline agriculture.