| This essay was aimed to study the morphological and physiological characteristics in the condition of low temperature on Alnus cremastogymeand Alnus formosana. By observing the morphological changes and the preservation rate of overwintering seedlings on different altitudes (900m,1350m,1650m); and measureing the parameters of Natural cooling process and laboratory artificial low-temperature REC,chlorophyll content, soluble protein content, soluble sugar content, proline content, SOD activity, POD activity, MDA content, the results showed that:(1) Two species of the alder both had the ability to adapt to cold resistance and low temperature. The seedlings of A. cremastogyme that could survive in winter at an altitude of 1350m had a wider Adaptation range than that of A. formosana,which could only reached 900m;After Cold Wave, both appeared brown spots on their leaves, and the spire became maroon.(2) The epicyte of the two species both could be hurt after suffering the Sudden temperature drop.They would be damaged seriously in natural environment;however,under the artificial hypothermia stress, the membrane permeability of two alder seedling would be revovered to a normal level.(3)During the process of artificial hypothermia, the chlorophyll content of two materials didn't have a significant changebut increased in natural cooling process,which were not be affect by cold wave. Low temperature of mainly affected the total chlorophyll,had little effect on chlorophyll a/b value.(4)Both artificial hypothermia and cold wave leaded the soluble protein content decline. After a period of cold adaptation, the soluble protein content of the material in artificial hypothermi could recover normally. And the content of soluble protein in A. formosana still maintain at a low level.(5) Under the cold stress, two species adapted to the change by adjusting the content of Soluble sugar, which reduced cell damage. A. formosana had a larger range of variation of the soluble sugar content than that of Alnus cremastogyme, which indicated that it was an important way to adapt to low temperature.(6)Under the effect of low temperature, two alder seedlings had a reaction periodfor the increase of praline, which of A. formosana was intensely than that of Alnus cremastogyme. Under the natural growth condition, the proline content of Alnus formosana was also higher than that of A. cremastogyme.(7) The SOD, POD activity of both alder seemed no different under the artificial cold stress and natural decreasing of air temperature process. In the artificial hypothermi stress, the activity of SOD, POD were increased, which was not related to the number of days. Through the self-regulation,the low temperature resilience of seedlings increasedwhile the SOD, POD activity decreased; In the natural cooling process, SOD, POD activity increased initiatively.During the cold wave, the SOD activity of A. cremastogyme significantly increasedwhile A. formosana changed stability. Both of the two alder seedlings had a stable POD activity. It can be explained that the Cold hardiness of the two the alders exist a genetic background.(8) By low temperature treatment, with the lipid oxidation of two alder leaves increased, MDA content increased.Under the artificial hypothermia stress, according to adjust their metabolism, both two species reduced the lipid oxidation and MDA content. In the process of natural cooling, the cell membraned by injuries, which resulted in the lipid oxidation intensify.The results showed that the two species of alder seedlings both had cold hardiness,which could help them overwinter in a certain altitude range.In the low temperature, the physiological indicators showed a dynamic change, and appeared some differences in their physiology. Two of these alders were both adapt to the artificial hypothermia in the natural environment. And the study also showed that A. cremastogyme had a better cold hardiness than A. formosana. |
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