Effects Of Cadmium And Aluminium On The Difference Of The Uptake Of Cadmium And Aluminium And The Growth Of Stylosanthes In In The Acid Soil

Soil acidification, resulting in decrease of soil acidity, increase of active aluminum content, and leaching of many heavy metal elements, is one of the major problems on global environmental change. Toxic aluminum and heavy metal was harmful for root systems and limits the development of plants. In this study, Stylosanthes scabra Vogel and stylosanthes guianensis were selected to research the difference of uptake and distribution of aluminum, cadmium and mineral elements in two different stylo species. Physiology responses to aluminum stress were compared in different Al-tolerant stylo varieties. The interaction of aluminum and cadmium to enzyme and development of microorganisms was investigated in acid soil. The main results are as follow:Two Al-tolerant varieties, cultivar10and cultivar107, and two Al-sensitive varieties, cultivar9and cultivar151, were screened out from more than100stylo varieties.The contents of MDA and H2O2, activity of SOD, CAT and POD, and relative conductivity increase distinctly in stylo leaves under Al stress condition at30μmol/L, but no effect on Pro content. Comparing with Al-sensitive stylo varieties, Al-tolerant varieties have stronger ROS-scavenging ability.Cadmium stress haves no effect on the content of MDA and Pro at less than10μmol/L in stylo, and enhances the content of MDA at100μmol/L. The responses of MDA, POD and CAT under cadmium stress indicated that Reyan No.2was more sensitive to cadmium than TPRC2001-1and Reyan No.13.The results of soil cultivation experiments indicated that aluminum stress can decrease the soil pH and enhance active cadmium content and leaching of three microelements including Mn, Zn and Fe at50mg/kg in soil. The effect on soil acidity order was as follow:Al+Cd> Al> Cd. The interaction of aluminum and cadmium significantly enhance the active cadmium content in soil.Al stress can enhance the content of Al in stylo root and Cd in stylo root and shoot, but no effect on the content of Al in stylo shoot. Both Al and Cd stress can enhance the content of K and Mg, but no effect on Ca, Fe and P in stylo shoot. Al stress can decrease Zn content, but increase the content of Fe, Mg, Mn and Zn in stylo root system. Under soil cultivation, Al stress promote the uptake of Ca, however, Al stress inhibit the uptake of Ca under water cultivation. The uptake of Al and Cd was lower in Stylosanthes scabra Vogel than Reyan No.2and Reyan No.13.The limitation of enzyme activity order was as follow under Al stress condition: phosphatase> catalase> dehydrogenase> urease. Cadmium stress can decrease the dehydrogenase activity and increase the urease active, but no effect on phosphatase and catalase activity. The interaction of aluminum and cadmium significantly limit the activity of catalase and dehydrogenase. Al has effect on enzyme related to the cycles of C and P. The appropriate cadmium stress was advantageous for the cycle of N. Al stress can limit CO2respiratory intenesity at1500-2000mg/kg, and Cd stress can enhance CO2respiratory intensity at50-1OOmg/kg.The limitation of soil microorganism order was as follow under Al stress condition: actinomycete> fungus> bacteria. The limitation of soil microorganism order was as follow under the interaction of aluminum and cadmium:fungus>actinomycete bacteria. Cadmium stress can limit the development of actinomycete and promote the development of fungus. Cadmium stress promotes the development of bacteria under low concentration. The effect of cadmium on the development of bacteria was complicated under high concentration.