Effects Of Drought Stress On The Growth And Active Constituents Of Bupleurum Chinense DC.

In order to explore the influence of the growth and active constituents of Bupleurum chinense under drought stress, the growth, photosynthesis, and the accumulation of Bupleurum saponin a and d of are studied through the pot under water control and PEG stress. The results could reveal Bupleurum chinense responsed to the drought environment, which will be conducive to people into an awareness of its growth situation under drought condition. Moreover it also provided the basis standardization cultivation of rational utilization of water for Bupleurum chinense. Main conclusions were as follows:1. The drought stress could induce the accumulation of bupleurum saponin a and d. Under 10% PEG stress, two saponins increased significantly(P < 0.01), on other hand under 20% PEG stress the content of bupleurum saponins was less than 10% PEG stress, which suggested that with the increase of drought stress, the content of bupleurum saponin was reduced.2. Under different drought degree, the study about bupleurum saponins gene expression of key enzymes and saponin content found: the expression of HMGR, IPPI, FPS, β-AS rised in several extent, the FPS and β-AS raised significantly. Each gene expression under 10% PEG stress quantity was higher than 20% PEG stress, which were consistent with the change of saponin content. Through the relativity analysis of gene expression and saponin content, there was significant positive correlation between saponin content and the expression of HMGR, IPPI, FPS, β-AS. Therefore, a certain degree of drought stress was beneficial to the accumulation of bupleurum saponins. Under drought stress Bupleurum chinense affected the synthesis of secondary metabolites of saponins by adjusting the branch point gene expression of key enzymes.3. The drought stress inhibited the growth of Bupleurum chinense. The plant height, stem diameter, leaf length, leaf width, leaf area decreased with the loss of the soil water content, and presented the trend of appropriate moisture > moderate stress> severe stress. Since the drought increased, the thick of root decreased and root length increased. Soil moisture content related to leaf relative water content. The content of soil water high and the leaf relative water content was high. All the processing water content remained above 60% and showed that the retention ability of leaf water was strong. However as the stress degree increased, the cell membrane relative permeability and cell membrane damage increased.4. The influences on leaf chlorophyll content, photosynthetic gas exchange and photosynthesis under different water treatment of Bupleurum chinense, the results showed that the diurnal change of photosynthetic rate was typical bimodal structure and 12:30 was photosynthetic lunch break points. This special mode was an effective way to adapt to drought and plant could reduce water loss and avoid photosynthesis system were destroyed. The content of photosynthetic pigment reduced, severe stress decreased significantly; Pn,Tr,GS decreased different level and Ci slightly increased in moderate stress. The Pn decreased mainly caused by leaf area reduced, which making the photosynthetic area reduced, and the pores closed. Tr was weakened by plant transpiration to reduce the necessary way to moisture loss; GS and Ci was influenced by the size of the stomatal opening to adjust. In order to reduce the water loss, water deficit condition stomata closed or partially closed, which affected the carbon dioxide, the accumulation of photosynthetic product. Drought stress was bad for leaf photosynthesis of Bupleurum chinense.