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In this paper, a 1-year-old Yang Tong seedlings as research materials, potted artificial simulation of soil drought stress weighing replenishment method (set a field capacity of 15%, 30%, 45%, 60%, 75%, W1, W2, W3 , W4, CK said), to study different drought stress the extent and stress time Yang Tong Miao's growth, physiological and biochemical characteristics, explore Yang Tong seedlings to drought stress of adaptation mechanism and capacity, in order for the different site conditions in cultivation Yang Tong provides theoretical basis. The main findings are as follows: 1. Drought stress inhibited Young Tong height, diameter, leaf area, leaf number and biomass, but increased shoot ratio, that drought stress will change the distribution ratio of the the the Yang Tongsheng volume in the various organs, root ratio increase and decrease in leaf area will facilitate the absorption of water and maintain water balance under drought conditions. Drought stress so that Yang Tong seedlings relative water content decreased prophase reduction plants active accumulation of soluble sugars and proline to osmotic adjustment. Drought stress, the soluble sugar and proline content increased and Yang Tong Ye sheet has some water retention capacity. Experimental late leaf relative water content decrease the soluble sugar falling later in the experiment, it may be due to organic synthesis rate decreases due to damage to the photosynthetic apparatus. Soluble protein during the experiment, the overall downward trend, with the downward trend of the decline in soil moisture, soluble protein as osmotic adjustment substance. 3 under drought stress, SOD and POD activity showed a rising trend in the removal of reactive oxygen, performance for Yang Tong Ye film malondialdehyde content and cell membrane permeability increased marginally. Experimental late enzyme activity is lower than that of the control, showed Yang Tong Ye film MDA content and cell membrane permeability on the drop by a big margin, and the blade relative membrane permeability and presents a positive correlation between MDA, to illustrate a certain level of coercion time, Yang Tong able to activate the SOD, POD activity of to regulating stress causing injury. Soil drought stress Yang Tong chlorophyll content decreased, but Chla / b value increased, chlorophyll b and chlorophyll a are more susceptible to damage, while increasing the content of carotenoids to absorb the remaining energy quenching inactivated oxygen to prevent membrane lipid peroxidation. Drought stress Yang Tong photosynthetic rate, water use efficiency, reduce the concentration of carbon dioxide in the intercellular intercellular carbon dioxide concentration among the treatments are not significant. Fv / Fm did not change significantly when more than 45% of field capacity at this time does not cause light to suppress the occurrence of the phenomenon. But in varying degrees of drought stress under ETR фPS II, qP decreased drought stress reduced the degree of openness of the PSII reaction center, causing a decrease in the rate of electron transfer, eventually leading to a decline in photosynthetic capacity. These results show that the non-stomatal factor is the main factor in the decline in photosynthetic capacity.
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