Effects of selenium stress on photosynthetic pigment contents and growth of Chlorella vulgaris.

Changes in photosynthetic pigment and protein contents, growth and the spectral characteristics in Chlorella vulgaris in response to selenium stress were investigated. Carotenoids (beta-carotene and xanthophylls) and chlorophyll (Chl a and Chl b) contents in cells exposed to Se 50 mg/L increased primarily and decreased afterwards, while photosynthetic pigments in cells exposed to Se 800 mg/L decreased significantly. Chlorophyll (Chl) absorption peak at 693 nm and prominent Chl emission peak at 700 nm, weakened significantly after Se stress. The excitation spectra showed a decrease in excitation energy transfer efficiency in Se-stressed cells. Total soluble protein decreased after Se stress. The changes in total Se, Mg(2+), Ca(2+), K(+) and Na(+) concentrations in culture medium and cells were also determined by ICP-AES.