Studies On The Effects Of Medicament Treatment On Improving The Heat-resistance Of Rhododendron Moulmainense

In this paper, initially explored the impact of heat stress on morphological and physiological characteristics of R.moulmainense and the effect of different thermal agents(chitosan, salicylic acid, calcium chloride) on heat resistance of R.moulmainense. The main research results are as follows:(1)Under different temperature stress(23℃、35℃、42℃、48℃),with the change of stress time(0h, 24 h, 48 h, 96h),there were significant differences in the changes of physiological indexes in the leaves of the R.moulmainense seedling(P<0.05). In the range of experimental temperature gradient, the temperature of 42 degrees is the limit temperature. Through comprehensive analysis, R. moulmainense can withstand high temperatures of 35 ℃, can not tolerate 42 ℃ and above.(2)Through observing the features and the recovery situation of R.moulmainense and studying the effect of heat treatment on the heat resistance of the R.moulmainense seedling, the conclusion that the higher the stress temperature is, the more damage to the plant can be found. Heat-resistant agent is helpful to improve the high temperature tolerance of the plant and protect the plant from the high temperature damage. The performance of treatment 3( 90mg/L CTS+60mg/L SA+900mg/L CaCl2) and 4( 120mg/L CTS+90mg/L SA+1200mg/L CaCl2) is better at 23 ℃. The performance of treatment 7(90mg/L CTS+90mg/L SA) is best at 35 ℃. The performance of treatment 10( 60mg/L CTS+90mg/L SA+900mg/L CaCl2)is best at 42 ℃. The performance of treatment 13(90mg/L SA+600mg/L CaCl2)and 14(60mg/L CTS+60mg/L SA)is better at 48 ℃.(3)The physiological indexes of R.moulmainense leaf were varied with spraying heat-resistant agent, and the increase or decrease variation amplitude of the physiological indexes had a certain correlation with the heat resistance of the R.moulmainense seedling. Under high temperature stress, the application of heat resistant agent had a significant effect on the heat resistance of 2-3 year old R.moulmainense seedling. By stress time increasing, the interaction of physiological indexes in the R.moulmainense seedling was increased. By means of correlation analysis of each index, the correlation between MDA and soluble protein, superoxide dismutase and chlorophyll were negatively correlated with each other. Soluble protein, proline and chlorophyll were positively correlated with each other. The correlation coefficient reached a very significant level in the late stress(P<0.01). Superoxide dismutase and proline had a significant positive correlation(P<0.05) in 48 h stress, and they were negatively correlated in 96h(P>0.05).(4)Under different temperature, the principal component analysis of the R. moulmainense’s morphology performance indexes, physiological and biochemical indexes and photosynthetic characteristics indexes shows that, more than 82.19% of the original data information is reflected by three principal components.Mainly includes the main components 1- "photosynthetic pigment and membrane lipid peroxidation factor", the main component of 2- "enzyme protection factor", the main component of 3- "protein factor". The principal component 1(chlorophyll(a+b), chlorophyll a, chlorophyll b, MDA) has highest contribution component, which reaching to 55.26%, indicates that the photosynthetic pigment and membranous peroxidation products is the main index to evaluate the R. moulmainense’s heat resistance.(5)The primary and secondary effects on each factor in the orthogonal test shows that the effect of temperature on the physiological indexes is great, and the main factors of different indexes are different. Using fuzzy mathematics membership function method to comprehensively evaluate the heat resistance of 19 treatments of R. moulmainense. The results show that the heat resistance of R. moulmainense seedling among the different treatments is different, and the ability of heat resistance in heat-resistant reagent treatment group is higher than the control group. Compared with the effect of the combination of heat resistant reagent under the same temperature, the following are results:23℃: The performance of treatment 3(90mg/L CTS+60mg/L SA+900mg/L CaCl2)is better;35℃: The performance of treatment 6( 60mg/L CTS+1200mg/L CaCl2) is better;42℃: The performance of treatment 10(60mg/L CTS+90mg/L SA+900mg/L CaCl2)is better;48℃: The performance of treatment 13(90mg/L SA+600mg/L CaCl2)is better.The evaluation result is basically consistent with the actua observation.