The Physiological Responses Of Upland Rice To Salt Stress

Upland rice is a special ecotype in cultivar rice. Compare to cultivar rice, it has the tolerances to drought and poor fertility, as well as a wide resistances. The tolerance to salt stress of three types rice roots, resistance of zhenghan-2, semi-resistance of Yujing-2 and normal of Yujing-6, was investigated in the present study. The membrane permeability, MDA and proline contents, the accumulation and scavenging of ROS (reactive oxygen species) under salt stress were determinded. The aim is to better understand the character of physiological response to salt stress in upland rice. The main results were summarized as follows:The relative water content in root of all rices decreased and the membrane permeability in root of all rices increased with NaCl concentrations increase and time extension,whose degree in Zhenghan-2 root was far less than that of Yujing-2 and Yujing-6 under the same salt stress. MDA contents in three rice roots increased with NaCl concentrations increase under 0-75 mM NaCl stresses. At the present of 75-200 mM NaCl, the MDA contents in Yujing-2 and Yujing-6 roots also increased with NaCl concentrations increase and reached the maximum at 150 mM NaCl. The MDA content in Zhenghan-2 root, however, was almost no increase, and MDA content in Zhenghan-2 was always lower than that of Yujing-2 and Yujing-6 in salt stresses.2, Proline is a cytoplasmic osmoticum and operates a very important role in plant resistances. The proline content in Zhenghan-2 root under salt stresses was higher than that of Yujing-2 and Yujing-6 roots. The maximum of proline content in Yujing-2 and Yujing-6 roots was observed in the present of 100mM NaCl at 4 days under different NaCl concentrations treatments. They are about 13.98mg/gFW and 13.01mg/gFW, respectively. But the proline content in Zhenghan-2 root reached a maximum 17.58mg/gFW at 150mM NaCl. These results indicated that the accumulation of proline in Zhenghan-2 root was higher than that of Yujing-2 and Yujing-6 roots under salt stress. And the tolerance of Zhenghan-2 to salt stress was stronger than that other two rices.3s The activities ofantioxidant enzymes (SOD, POD, CAT, APX) in Zhenghan-2 root under salt stress were all higher than that of Yujing-2 and Yujing-6 roots. The content of H2O2and 02'in Zhenghan-2 root was lower than those of Yujing-2 and Yujing-6 roots under salt stress. These results demonstrated that the higher activities of antioxidant enzymes in Zhenghan-2 root under salt stress could be good for scavenging ROS induced by salt stress, and the oxidative damage of Zhenghan-2 in salt stress was reduced.4> The membrane permeability and O2" content in three rice roots decreased in the present of H2O2 either in the control or in salt stress. The more decreases of them were appeared in Zhenghan-2 root under salt stress. Application of CAT, as a H2O2 scavenger, revealed that both of them in three rice roots increased markedly either in control or in salt stress. These data suggested that H2O2 could act as a signal in resistance of Zhenghan-2 to salt stress.In summary, Zhenghan-2, an upland rice with strong resistance to drought, also had strong tolerance to salt stress. The physiological characters of Zhenghan-2 to salt resistance could be marked accumulation of proline, maintaining the stability of cell membrane and higher antioxidant enzymes activity etc.