Impact Of Cadmium Contamination On Growth And Photosynthesis Of Salix×Au Reop Endula And Vefiveria Zizanioides

After up-build of the Three Gorge reservoir, vegetation degenerate will happen case of long time flooding. This will enhance soil erosion in this area. Using plant for revegetation the riparian area in Three Gorge reservoir region is very important to the safety of the Three Gorge reservoir. Pollution in this area is also very serious, especially of heavy metal pollution, and cadmium pollution is the most serious heavy metal in this area. So study the effects of cadmium on the flooding- resistant plant species' growth is very important.This research based on the background of cadmium content in Three Gorge reservoir area, to study the change of growth, photosynthetic rate and chlorophyll fluorescence of two flooding-resistan plant species, Salix×au reop endula and Vefiveria zizanioides.Cadmium brought about significant reduction in willow's stem length with the concentration and the days which in the treatment was enhanced. Willow's total plant biomass and biomass above ground were not influenced significantly, but the root's biomass was reduced significantly under 80mg/kg Cd²⁺ concentration and long time treated. The effect of cadmium on Vefiveria zizanioides's tiller was weak. With long time treated, total plant biomass, above ground biomass and root biomass were decreased with concentration of Cd²⁺ increased. The effect of Cd²⁺ on the two species showed that, the root endured more intimidation than the above ground part.In short time, cadmium did inapparent effort to willow chlorophyll content, but at high Cd²⁺ content, the chlorophyll a/b ratio was increased. At long treatment time, total chlorophyll, chlorophyll a, chlorophyll b and pigment of carotenoid were increased by all Cd²⁺ treatments; they hoist first, and then fall with enhancing Cd²⁺ concentration. And, cadmium did more efforts to chlorophyll b and pigment of carotenoid than other chlorophyll index. Cadmium did no significant difference in content of chlorophyll to Vefiveria zizanioides at short treatment time. With long treatment time, especially at high lever of Cd content, all chlorophyll content were increased. From the change of chlorophyll content, Vefiveria zizanioides has a better tolerance to cadmium than willow.Low lever of cadmium content decreased Pn of willow at short treatment time, and Pn gradually decreased with enhancing treatment concentration and time. Fv/Fm and Fv'/Fm' decreased at higher lever of cadmium in the long time treatment, OPSâ…¡and ETR decreased a litter at low lever of cadmium and short time treatment, with long time treatment, the effects of Cd²⁺ on OPSâ…¡and ETR was weak. q_p decreased at low lever of cadmium and short time treatment, but increased with enhancing treatment time. Cd did significant effects on photosynthesis and fluorescence of Vefiveria zizanioides. Pn gradually decreased with enhancing treatment concentration and time. Fv/Fm had no significant effect with Cd²⁺ treatment concentration and time. Fv'/Fm',ΦPSâ…¡, ETR and q_p were increased at Cd²⁺ concentration of 20, 80mg/kg and short time treatment, with enhancing time, these hasten were decreased. The results showed that, Vefiveria zizanioides has a better tolerance than Salix×au reop endula.In general, cadmium can reduce the biomass, affect the chlorophyll content, reduce the photosynthetic rate and change chlorophyll fluorescence index. Though, cadmium bated the two species's growth more or less, the two can grow well indeed. And when the content of Cd²⁺ at 2mg/kg, to Vefiveria zizanioides, the growth was even enhanced, this content of Cd²⁺ is familiar in the Three Gorge reservoir. That is, Salix×au reop endula and Vefiveria zizanioides has a potential to used for revegetation of riparian area in Three Gorge reservoir region.