Physiological response of Solanum nigrum to salt stress

The effects of salt stress (100, 200, 300 mmol/L) on physiological characteristics of Solanum nigrum seedlings were studied by pot experiment. The results showed that the contents of chlorophyll a, chlorophyll b, carotenoids and total chlorophyll in S. nigrum leaves showed a trend of first flattening and then increasing with the aggravation of salt stress. With the aggravation of salt stress, the net photosynthetic rate, stomatal conductance and intercellular CO2 concentration of S. nigrum decreased gradually, and reached the lowest value when the NaCl concentration was 300 mmol/L. With the increase of NaCl concentration, the SOD activity of S. nigrum leaves decreased gradually. When the concentration of NaCl was 300 mmol/L, the SOD activity of S. nigrum decreased by 53.39% (P < 0.05). The activities of POD, CAT and soluble protein in S. nigrum increased first and then decreased with the increase of NaCl concentration. When the concentration of NaCl was 100 mmol/L, the activities of POD, CAT and the content of soluble protein reached the maximum.