Effects Of Different Soil Water Contents On Sufur Metabolism Of Robinia Pseudoacacia And Hippophae Rhamnoidesl. Subsp Sinensis

Three degrees of soil water content treatments were adopted by the maximum soil capacity for holding water being 70%, 55% and 40%, to simulate the environment conditions with no water stress, mild water stress, and severe water stress respectively. Robinia pseudoacacia and hippophae rhamnoidesl. subsp sinensis seedlings were used in the study to investigate the influence of different soil water contents on sulfur metabolism. In order to explore protective effects of sulfur reduction and antibolism of glutathione antioxidant defense system to R. pseudoacacia and H. rhamnoidesl seedlings, we have investigated sulfate contents in xylem and, soluble protein contents, enzymes activity of ATPS and OASTL in sulfur reduction and glutathione antioxidative system both in leaves and roots. The results showed that:1,The content of sulfate in xylem of R. pseudoacacia and H. rhamnoides seedlings first increased with the increasing water stress and then decreased, which indicated that the ability of absorption and transportation to sulfate in the two plants improved under mild soil water stress and the sulfate contents decreased maybe because of excessive consumption.2,Soluble protein contents in leaves of R. pseudoacacia decreased under mild water soil stress or severe soil water stress, while increased in roots of R. pseudoacacia, which demonstrated the distress in leaves was severer than in roots of R. pseudoacacia. The content of soluble protein in H. rhamnoides increased in lesves with the enhanced water soil stress except that the extent of the change was narrower in severe soil water stress than in mild soil water stress, while these had no obvious change in roots under mild soil water stress or severe soil water stress, which indicated that the damage to the leaves of H. rhamnoides is light and soil water stress made no obvious change to the roots.3,ATPS activity of R. pseudoacacia increased obviously in leaves and lightly in roots under mild soil water stress and OASTL activity decreased distinctly in leaves but it had no obviously change in roots. ATPS and OASTL activity of R. pseudoacacia decreased in leaves and the variation range of average OASTL activity under severe soil water stress is similar with those under mild soil water stress, while average ATPS activity of R. pseudoacacia also increased in roots under severe soil water stress but the variation range is smaller than those under mild soil water stress, which indicated that the activity of sulfate reduction enzymes in R. pseudoacacia leaves changed a little but the trend of all the sulfate reduction enzymes activity was no obvious and the two sulfate reduction enzymes activity in roots had no obviously change. In other words, the sulfate reduction process of R. pseudoacacia in leaves had changed a little under mild water stress but the variation trend had no obvious and decreased under severe soil water stress. There was no obvious change on sulfate reduction of R. pseudoacacia roots under different soil water treatment.In H. rhamnoides, the change of ATPS and OASTL activity in leaves and roots of was no obvious under mild water soil stress. The activity of these two enzymes in leaves increased slightly under severe soil water stress and had no significantly change in roots, which indicated that the impact of soil water stress on the activity of the both enzymes was small in leaves and roots.4,The change of glutathione antioxidant defense system under different water treatment. The GSH and AsA contents as well as GR and SOD activities in roots was lower than in leaves of R. pseudoacacia whether under normal water condition or in water stress conditions. GSH-Px activity is higher in roots than in leaves only in severe water stress condition. The GSH contents of R. pseudoacacia first increased and then decreased in leaves, but gradually increased in roots. AsA content in leaves decreased whereas firstly it increased then decreased in roots with the increase of water stress. The activity of GR either in leaves or roots decreased according to the increasing of water stress and was considerably subnormal under severe water stress. The activity of GR in leaves was much higher than in roots no matter under what soil water conditions. The activities of GSH-Px and SOD in leaves increased under the mild water stress and decreased under the severe water stress, while GSH-Px and SOD activities in roots enhanced with the increase of water stress. The result revealed that GSH and GSH-Px of glutathione antioxidant defense system for R. pseudoacacia played an important role in getting rid of reactive oxygen species which caused by water soil stress. Therefore, improving GSH content and GSH-Px activity are the main means for R. pseudoacacia in responding water soil stress.In H. rhamnoides, the GR, SOD and GSH-Px activity and AsA content had no significant change in leaves under mild water soil stress, but GSH content increased and the whole trend of GSH variation was significant. The activity of both GR and GSH-Px, as well as contents of GSH and AsA in leaves increased under severe water soil stress. GR activity and GSH content decreased and the GSH-Px activity and AsA content increased in roots under mild water soil stress, but all the changes had no significant. Under severe water stress,Both activity in SOD and GSH-Px, also the contents of GSH and AsA separately in roots increased significantly, but all the variation had no significant. All result demonstrated that the variation of GSH content and GSH-Px activity of glutathione antioxidative defense system for R. pseudoacacia are the main way of coping with water soil stress.In conclusion, the drought-resistance of H. rhamnoides is stronger than R. pseudoacacia. According the results of this study, The roots of H. rhamnoides was no obviously influenced and leaves was impacted lightly by water soil stress. It means that H. rhamnoides could maintain normal level of sulfate metabolism in different water soil stress. The impact to R. pseudoacacia leaves was small under mild water soil stress and great under severe water soil stress, while R. pseudoacacia roots was affected a little by severe water soil stress and was no significant influenced by mild water soil stress.