Effects of Mixed Neutral Salt Stress on Growth and Photosynthetic Physiology of Calendula officinalis Seedlings

Abstract:

In order to understand the response of Calendula officinalis seedlings to mixed neutral salt stress, the growth and photosynthetic physiology of seedlings was studied under stressed with NaCl∶Na₂SO₄ at mole ratio of 9∶1. The results showed that the balance of active oxygen metabolism and the integrity of cell membrane structure were maintained by enhancing activities of superoxide dismutase (SOD), peroxidase (POD), catalase (CAT), and decreasing content of malondialdehyde (MDA) in leaves of C. officinalis seedlings under lower than 100 mmol L^-1 salt concentration, which could maintain normal photosynthesis and growth of seedlings. When salt concentration was more than 200 mmol L^-1, the activities of SOD, POD and CAT decreased rapidly, and content of MDA increased rapidly, which significant influnced on photosynthetic capacity and growth. Therefore, the threshold salinity of C. officinalis seedlings to mixed neutral salt stress was 100 mmol L^-1, the seedlings could maintain normal metabolic balance by regulating protective enzyme system.