Effects of Pb and NaCl stress on the physiological and biochemical characteristics of cucumber seedlings

An experiment was conducted in order to study the injury mechanism of cucumber seedlings under Pb,NaCl and their compound stress. Soil culture experiments were also carried out to study the physiological and biochemical characteristics of cucumber seedlings by applying different levels of Pb(0.5 and 1.5 mmol/L) and NaCl(50 and 100 mmol/L) compound in the soil.The results showed that drastic decrease in the contents of chlorophyll a,chlorophyll b and chlorophyll a+b of cucumber leaves with increasing Pb and Nacl concentration;In comparison to the control,the relative conductivity and MDA content of cucumber seedlings increased significantly,and ones under 100 mmol/L NaCl treatment were higher than 1.5 mmol/L Pb treatment;The soluble sugar content,proline content,and the activities of SOD and POD increased greatly compared to the control,and ones under compined stress were higher than single stress.Toxic effect of Nacl on the physiological and biochemical characteristics of cucumber was stronger than Pb;and the toxic effect of Pb and Nacl compound stress was always higher than the individual stress.