Physiological and antioxidant responses of Basella alba to NaCl or Na2SO4 stress

Salinity is a major factor negatively affecting plant growth and agricultural productivity. To gain a better insight into Basella alba responses to different salt stress, some physiological parameters were investigated on this species after 15-day exposure to 200 mM NaCl or 100 mM Na2SO4 stress. Plant growth was significantly suppressed under salinity and a more pronounced impairment induced by NaCl instead of Na2SO4 was observed. A high level of water content was maintained in salt-treated shoot. Salinity stress caused marked increase in Na+, Ca2+, Cl− and SO42− concentrations and decrease in K+ level and K+/Na+, Ca2+/Na+ and Mg2+/Na+ ratios in plants. The absorptive abilities of K+, Ca2+ and Mg2+ in plants were improved significantly under salinity. Plants suffered a deeper oxidative stress in the presence of NaCl than Na2SO4 as evidenced by the higher increase in foliar superoxide anions (O2·−) and malondialdehyde (MDA) production as well as electrolyte leakage. No salt-induced alterations were observed on foliar hydrogen peroxide (H2O2) level. B. alba responded to the oxidative stress by enhancing antioxidant capacity involving ascorbate, reduced glutathione as well as antioxidant enzymes. Superoxide dismutase (SOD), ascorbate peroxidase (APX) and glutathione reductase (GR) were all involved in the detoxification of reactive oxygen species (ROS) in plants exposed to salt stress, whereas catalase (CAT) only functioned in the Na2SO4-treated plants. The ability of water maintenance in shoot and improvement of cation absorbability as well as enhanced foliar antioxidant capability all contribute to the salt adaptation of B. alba, whereas a more efficient cation transport system and antioxidant mechanisms may be responsible for the better acclimation of this species to Na2SO4 than NaCl.