EFFECTS OF SIMULATED SO2 POLLUTION ON SUBTROPICAL FOREST SUCCESSION: TOWARD CHLOROPHYLL FLUORESCENCE CONCEPT

The effects of simulated SO2 treatment (NaHSO3 with different concentrations) on chlorophyll fluorescence in five subtropical forest plants, namely Pinus massoniana Lamb, Schima superba Gardn., and Champ, Castanopsis fissa R and W, Acmena acuminatissima Bi.merr., and Perry, and Cryptocarya concinna Hance, were investigated. After the leaf sections were immersed in 0, 20, 50, 100 mM NaHSO3 for 10 h, the low temperature (77 K) chlorophyll fluorescence emission, FPSI/FPSII ratio and chlorophyll fluorescence induction curves of all five woody plants reduced to different extents, while an increase in low temperature fluorescence polarization was found. Shortterm treatment of SO2 damaged PSII, decreased the fluidity of thylakoid membrane, and affected the process of electron transport. Sulfite oxidase activities of five plants grown in three light environments (100, 32, and 12% of natural light intensities) were varied, which showed different resistance to SO2 pollution. A. acuminatissima and C. concinna, the dominant species in the late succession stage of a subtropical forest in South China, was less sensitive to SO2 pollution. And P. massoniana, the pioneer heliophyte species was less able to resist NaHSO3. It is suggested that SO2 pollution may accelerate the succession of subtropical forest.