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Macropanax rosthornii is a wild plant to be exploited and utilized with high medical and ornamental value. It grows well in cool, wetness and shady environment, but it is often injured by high temperature stress in the state of being cultivated. When Macropanax rosthornii seedings were exposed to high temperature, we observed its growth and structure changes, and measured and analyzed some physiological characters such as soluble saccharine(S) content, soluble protein(Pr) content, MDA content, relative conductivity, activities of SOD and POD, chlorophyll(Chl) content, chlorophyll fluorecence parameters. The main results obtained are as follows:(1)The morphological changes of Macropanax rosthornii were not remarkable under 30℃and 35℃temperature stress. Under 40℃high temperature stress, leaves, which was deformed seriously, turned yellow; their biological activities were lost, and the ends of twigs were browned.40℃is the limiting temperature for the growth of Macropanax rosthornii.(2)The leaf constructure had no changes under 30℃and 35℃temperature stress, but under 40℃temperature stress, it changed greatly. Stoma density rose, stomatal size and stomatal index of length and width reduced; palisade tissue and spongy tissue showed irregular arrangement; chloroplasts were congregated, seriously damaged and perforated.(3)The soluble saccharine content and soluble protein content had little changes under 30℃and 35℃temperature stress. They increased along with the prolongation of 40℃high temperature stress, and had a positive correlation to the days of high temperature. The high temperature(40℃) stress had a remarkable effect on soluble protein content.(4)Both the conductivity and MDA content rose first then fell to CK’s level under 30℃and 35℃high temperature stress, increased along with the prolongationn of 40℃high temperature stress.The conductivity had a strong positive correlation to the days of high temperature, the relationship between MDA content and days of high temperature stress is a positive correlation.(5)The SOD activity rose first, then declined rapidly under 30℃and 35℃temperature stress, and the POD activity rose first then kept stable. The days of high temperature, had a negative correlation to SOD activity. There was a negative straight line between the days of high of high temperature and POD activity.40℃high temperature stress had a remarkable effect on POD activity.(6)Chlorophyll a、total chlorophyll and the ratio of chlorophyll a/b fell then rose under 30℃,35℃and 40℃high temperature stress, but chlorophyll b had little changes.(7)Fo,qN,qP had little changes under 30℃and 35℃temperature stress, Fv、Fm、Fv/Fo、Fv/Fm,Yield,ETR fell first then rose to a normal level. Fv,Fm,Fv/Fo,Fv/Fm,Yield,ETR,qP and qN fell obviously under 40℃high temperature stress.(8)The CMT of Macropanax rosthornii is 51.79℃by the Logistic equation.
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