Study On Cold Resistance Physiology Of Michelia Maudiea Dunn.sapling

This paper, with 2-year sapling of Michelia maudiae Dunn. as its research object,has studied its changes in physiological characteristics when sprayed with the three solutions of Pro, Vc and CaCl₂ in the simulated winter low-temperature and in the four conditions of different temperature reduction speeds, different temperature reduction ranges, different duration of low temperature and different temperature increase speeds. The results are as follows.1. In the experiment of simulated winter low-temperature,the spraying of the three solutions of Pro, Vc and CaCl₂ to a certain extent increased the activities of SOD and the content of SS and Pro and decreased relative conductance and the content of MDA, which led to the preliminary conclusion that the spraying of the three solutions can increase cold resistance of M.maudiae Dunn. to a point. The increase only occurred in the small reduction temperature ranges, changed little in the turning point temperature and it was not obvious in low temperature. Comprehensively speaking, the spraying of Pro had the best effect, Vc rated second and CaCl₂ ranked last. But the spraying of the three solutions didn't work the same in increasing the inspected index. That is, the spraying of the same solution didn't produce the same effect in increasing the index of cold resistance of M.maudiae Dunn., with little effect in some cold resistance index and with obvious effect in another cold resistance index, in other words, they didn't increase the cold resistance of M.maudiae Dunn. in every way. Therefore, whether the cold resistance of M.maudiae Dunn. has increased or how big it is can't depend solely on a certain index. 2. In the experiment in the conditions of different temperature reduction speeds, different temperature reduction ranges, different duration of low temperature and different temperature increase speeds, the activities of SOD,the content of SS and Pro and relative conductance were to a certain extent minus related, and not closely related. That shows the complexity of the formation of cold resistance of M.maudiae Dunn. and its reactions to low temperature. The cold resistance came into being under the comprehensive circumstances of all sorts of interweaving metabolisms.There is much differrence in the activities of SOD,the content of SS , MDA and Pro, etc, measured before the application of low temperature , but comparatively, relative conductance is concentrated and there is not much difference. It shows that there is much difference among individual s of M.maudiae Dunn., which partly resulted in the phenomenon that the measured index were not closely related.3. In the experiment of rapid temperature reduction, in the condition of the same temperature reduction ranges, the measured index did not change one by one according to the temperature reduction speeds, while the measured index are quite different in different temperature reduction ranges. It shows that without the practice of low temperature, the different temperature reduction speeds (within 48 hours) had little effect on M.maudiae Dunn., but the different temperature reduction ranges had a big effect. The activities of SOD and the content of SS basically maximized at the end of the temperature reduction stage, but in terms of relative conductance, M.maudiae Dunn. are affected most in the duration stage of low temperature. The stage of temperature increase, useful for M.maudiae Dunn. to recover from damage, had little effect on it.