中文摘要：

经模拟低温（-12、-8、-4、0、4℃）胁迫处理后,长苞铁杉幼苗叶片和根系相关生理指标均发生明显变化.随着温度降低,叶片光合色素含量增加,但反映光合活性强弱的Chla/Chlb降低;叶片中渗透调节物质脯氨酸和可溶性糖含量增加,呈极显著正相关（r=0.804,p〈0.01）,根系中可溶性糖含量的减少说明根对低温胁迫的渗透调节更依赖于脯氨酸的累积.幼苗在-4℃及更低温度胁迫下受到严重的冻害使SOD活性持续下降,叶片中POD活性与SOD活性变化呈极显著负相关（r=-0.908,p〈0.01）,但根系中POD活性与SOD活性没有相关性,说明长苞铁杉幼苗对抗外界胁迫机理的复杂性.叶片MDA含量比根系低可能与叶片中Car能缓解1O2对细胞的伤害有关.

英文摘要：

The activities of superoxide dismutase （SOD） and peroxidase （POD）,content of photosynthetic pigment, proline, solu- ble sugar and malondialdehyde （MDA） in the leaves and roots of Tsuga longibracteata seedling were studied under the simulate low temperature stress （- 12, -8, -4,0,4 ℃ ）. The experimental results indicate that with decreasing temperature, content of photosyn- thetic pigment in leaf increased,but the ratio of chlorophyll a and chlorophyll b （Chla/Chlb） which reflected activity of photosynthesis reduced. There is positive correlation between proline and soluble sugar which increase in the leaves （r=0. 804, p〈0.01）. Moreover,osmoregulation in the roots depend on cumulation of proline because of the decrease of soluble sugar. The activity of SOD in the seedling leaves declined gradually blow -4℃. There is a positive correlation between the activities of SOD and POD（r=-0. 908,p〈0.01）in leaf,but without correlation in the root. It also show the complexity of mechanism which the seedling of Tsuga longibracteata resist the environment stress. Lower content of MDA in leaf may due to the increase of carotenoid （Car） which decrease injury of cell by ^2O2.