Effects of NaCl and Cd on photosystem II (PS II) activity of Chlorella pyrenoidosa

Abstract

The effects of NaCl and cadmium (Cd) on photosystem II (PSII) activity of Chlorella pyrenoidosa were investigated by chlorophyll fluorescence test to detect the changes of PS II performance caused by environmental stress. NaCl concentrations in media were set as 0, 25 and 100 mmol/L and CdCl 2 concentrations in media were 0, 1, 25 and 100 μmol/L. The fluorescence parameters were detected after exposure for 1, 3, 6, 12 and 24 h, respectively. The results showed that the PS II efficiency and the number of reaction centers decreased under stresses of high levels of NaCl (≥25 mmol/L) and Cd (≥25 μmol/L). The inhibition of NaCl was more related to the light dependent reaction by decreasing the quantum yield for electron transport. The main target site of Cd was the PS II reaction center by increasing the absorbed energy and dissipation in each reaction center. The PSII activity was enhanced by low concentration Cd (1 μmol/L). The effects of NaCl and Cd depended on their concentrations and exposure time, which had synergistically inhibitory effects on PSII activity.