Effects of Cadmium Stress on Leaf Chlorophyll Fluorescence and Photosynthesis of Elsholtzia argyi-A Cadmium Accumulating Plant

摘要

A hydroponic experiment was conducted to investigate the effects of cadmium (Cd) on chlorophyll fluorescence and photosynthetic parameters on a Cd accumulating plant of Elsholtzia argyi. Four weeks-seedlings of E. argyi were treated with 0 (CK) 5, 10, 15, 20, 25, 30, 40, 50 and 100 mu mol L-1 Cd for 21 days. Fv/Fo, Fv/Fm, qP, Phi PSII, ETR and Fv'/Fm' were significantly increased under low Cd (5-15 mu mol L-1 for Fv/Fo, Fv/Fm and qP, 5-10 mu mol L-1 for Phi PSII, ETR and Fv'/Fm') stress, and these parameters were similar to control under Cd = 50 mu mol L-1. All above parameters were significantly decreased at 100 mu mol L-1 Cd. Compared with control, Pn was significantly (P0.05) increased under 5-30 mu mol L-1 Cd. However, 50 and 100 mu mol L-1 Cd significantly (P0.05) reduced it. Gs and Tr were substantially decreased at 50-100 and 40-100 mu mol L-1 Cd, respectively. Ci was significantly increased at 50 and 100 mu mol L-1 Cd. High Cd-induced decrease of Pn is not only connected to stomatal limitation but also to the inhibition of Fv/Fo, Fv/Fm, Phi PSII, qP, ETR and increase of NPQ. Maintain chlorophyll fluorescence and photosynthesis parameters under its Cd tolerance threshold were one of tolerance mechanisms in E. argyi.