C4 Photosynthetic Characteristics and Antioxidative Protection of C3 Desert Shrub Hedysarum Scoparium in Northwest China

To understand the adaptive mechanisms, and the strategy and direction of evolution of exploiting plants for living in oasis-desert transitional areas where there was a water gradient, mechanisms of C4 photosynthesis and antioxidative protection were studied in leaves and assimilating shoots of C3 desert shrub Hedysarum scoparium under water gradient accompanied with high irradiance and high temperature in simulated water gradient trial site that lies in the desert. In this study, C4 pathway was detected in the leaves and assimilating shoots of H. scoparium and the antioxidative enzymatic system was found to be very important in the protection against oxidants, both increasing considerably antioxidative enzymes and C4 photosynthetic enzymes under increasing water stress in C3 plant. The results indicated that the C4 photosynthetic response of assimilating shoots was more positive than that of leaves with water condition exacerbate. It was proposed that the direction of evolution of organs of C4 photosynthesis and positive interaction between antioxidative enzymes and C4 photosynthetic key enzymes in C3 desert species were important factors for plant growth, survival and reproduction in water gradient environment.