Physiological Response Mechanism And Inhibition Effect Of Cadmium Stress On Chamaecrista Rotundifolia

Chamaecrista rotundifolia from Australia since the 1980s is a kind of leguminous forage, which has large biomass, strong resistance. It can be used in the orchards intercropped, reconstruction of barren hills, water and soil conservation and ecological restoration, etc. Therefore, it is suitable to cultivate widely in subtropical regions. In this study, the method of the soil pot experiments with red soil was applied ⅰ) to study physiological response of Chamaecrista rotundifolia under cadmium(Cd) stress, ⅱ) identify the characteristics of Cd absorption characteristics and the main nutrient elements uptake in the Chamaecrista rotundifolia, ⅲ) to clarify the effects and mechanisms of Chamaecrista rotundifolia alleviating Cd stress. In order to chose a remediation plant to restore Cd polluted soil in mines of south red soil region.The results obtained are summarized as follows:1、The water pot test showed that Cd stress inhibited the growth of Chamaecrista rotundifolia CIP86134 and ATF3248, and the inhibition gradually strengthened with the increasing of Cd concentration. The uptake of Ca, Mg, Cu and Zn by two Chamaecrista rotundifolia cultivars were inhibited under Cd stress, but the elements accumulations of Ca, Mg, Cu, Zn in the above-ground and Ca and Mg in the under-ground of Chamaecrista rotundifolia CIP86134 were higher than Chamaecrista rotundifolia ATF3248. Cd absorbed by Chamaecrista rotundifolia was mainly concentrated in the under-ground. The translocation factor of CIP86134 was 0.04～0.07, ATF3248 translocation factor was 0.06～0.09. Different Chamaecrista rotundifolia varieties show different sensitivities to Cd stress, and ATF3248 was more sensitive than CIP86134.2、The soil pot experiment indicated that Cd stress inhabited the growth of Chamaecrista rotundifolia, and the biomass was reduced with the increasing of Cd concentration. At the Cd concentration of 4.0 mg/kg, the underground and aboveground biomasses were reduced by 59.7% and 63.8% when compared with the control, respectively. The synthesis of chlorophyll a, chlorophyll b and carotenoids was inhibited by Cd stress, and the inhibitory effect was gradually increased with the increase of Cd concentration, and there were significant differences among different treatments. The activity of POD was increased while the activity of SOD was decreased, and the activity of CAT was increased but decreased at the Cd concentration of 8.0 mg/kg. The Cd stress strengthened the peroxidation of membrane lipid of Chamaecrista rotundifolia and resulting in the MDA content increased. Cd-Mg, Cd-Zn showed synergistic effects at low Cd contentrations (1.0-2.0mg/kg) and antagonistic effects at high Cd contentration (4.0mg/kg). The Cd absored by Chamaecrista rotundifolia mainly accumulated in the under-ground and the translocation factor was only 0.15-0.29.3^ When added the red mud in soil, the available Cd concentration decreased and the absorption of Cd in Chamaecrista rotundifolia reduced with increased soil pH. When activate of antioxidant enzymes of SOD, POD and CAT, Chamaecrista rotundifolia resistance was enhanced the uptake and transfer to above-ground of N, P, K was increased and the growth obstacles caused by malnutrition was alleviated.