Eco-physiology Responses Of Mingshanbaihao To The Drought Stress

The Mingshanbaihao has been one of the key tea breeds of Sichuan Province and the other regions recently. And the drought has become the primary mishap, which could affect the productivity of crops and the other economic woods such as tea, and then led to the earnings incline of peasantry. Aimed to the need of production, the responses of Mingshanbaihao to the drought had been studied by artificial water regime. The growth and leaf morphologic, photosynthesis, physiology and bio-chemical indexes of Mingshanbaihao had been studied, and the indexes of growth and leaf morphologic, physiology and biochemical related to drought had been selected. The results indicated that:(1) Growth and morphologic responses of tea seedlings to the droughtDrought stresses had enhanced the injury of tea seedlings. The height and diameter at the base had been reduced significantly, and the biomasses of different component had been reduced significantly too while more of the biomass had been allocated to the root. In drought stresses, the characteristics of tea seedling leaf had been trended to those of the xerophil. For example, the whole dimension, horniness, barrier tissue of leaf had been thickened respectively. Following the aggravation of drought stress, the symptoms mentioned had become obviously.(2) Photosynthesis responses of tea seedlings to the droughtâ‘ Following the drought stresses strengthening, the net photosynthesis rate (P_n), transpiration rate (T_r) and stomatal conductance (G_s) had been significantly reduced separately. There're the positive relationships between P_n and G_s, P_n and T_r, T_r and G_s. Drought stresses had reduced the intercellular CO₂ concentration (C_i) significantly, while the stomatal limitation values and the water utilization efficiency (WUE) had been increased following the strengthening drought stresses. Therefore, the stomatal limitation was the key factor that led to the decrease of net photosynthesis rate.â‘¡According to the photosynthesis-light curve, the drought stress had enhanced the light compensation point (LCP), and dark respiration (R_d) significantly while the light saturation point (LSP), apparent photosynthetic quantum yield (α) and the maximum of net photosynthesis rate (P_max) had been decreased. So, the drought stress accelerated the tea seedlings to expend light, and reduced the tea seedlings to utilize light.â‘¢According to the photosynthesis-CO₂ curve, the drought stress had enhanced CO₂ saturation point, while the carboxylation efficiency (CE), CO₂ compensation point and the maximum of net photosynthesis rate had been decreased. That led to the restriction of tea seedlings to utilize CO₂.In a word, the parameters mentioned had been varied heavily following the aggravation of drought stress, which restrained the tea seedling's utilization of light and CO₂ obviously.(3) Physiology and biochemical responses of tea seedlings to the droughtFollowing the aggravation of drought stress, the content of osmotic adjustment substances and activity of enzyme in leaf had been enhanced. That represented as follows: the water content decreased significantly, the conductance, content of free proline, dissolubility sugar and malondialdehyde (MDA) increased significantly, and the dissolubility protein content and the activities of SOD, CAT and POD increased at the first and than decreased, which was one of the adjustment strategies to drought stresses.(4) Drought indexes of tea seedlings:â‘ Morphologic indexes related to Drought as follows (according to the order of correlation modulus from large to small, the same as below): growth of height, growth of diameter at the base, Biomass production, Biomass ratio of root and above-ground.â‘¡Physiology and biochemical indexes related to Drought as follows:water content of leaf,the content of free proline,malondialdehyde (MDA), the content of dissolubility sugar.