高寒山区植物根抗氧化酶系统的季节变化与抗冷冻关系

在高寒山区（海拔2900m）和选取4种多年生草本植物，即无芒雀麦（Bromus inermis）、草地早熟禾（Poa sphyondylodes）、花誉麦（Bromus sinensis）和垂重申披碱草（Elymus nutans），测定了秋末、冬初、冬季、春季气温变化过程中其根中丙二醛（MDA）含量和抗氧酶活力（过氧化氢酶（CAT）、过氧化物酶（POD）、超氧物歧化酶（SOD））和抗坏血酸氧化酶（APX）变化，分析了抗氧酶系统在根抗冷适应中的作用，结果表明，随秋末降温植物根中MDA含量增加，尔后下降，在冬季和翌年春季保持相对稳定。从9月初到10月下旬，4种植物根中SOD、CAT、POD活力平均增加170％、130％和56％。在冬季下降,但仍远高于9月，在春季气温上升过程中酶活力上升。根能在组织结冰状况下生存与其具备完善的保护酶系统，能及时清除氧自由基抑制膜脂过氧化维持膜完整性有关，据降温过程中MDA含量和抗氧酶活力变化，可将根冷适应分为两个阶段，即第1阶段平均气温在0℃以上，抗氧酶活力增强，MDA增加阶段，第2阶段平均气温降至0℃以下，最低气温降到－15℃以下，抗氧酶活力下降，MDA无明显变化阶段。

Seasonal changes in enzymatic antioxidant system in roots of alpine perennial forage grasses related to freezing tolerance

Four plants, Poa sphyondylodes, Bromus inermis, Bromus sinensis and Elymus nutans established in apline in 1993, were investigated throughout the winter and spring between 1995 and 1996 by monitoring MDA content and antioxidant enzymatic activities of SOD , CAT, POD and APX Roots were sampled at approximately 15 days interval in both autumn and spring Leakage of ions and MDA content increased,while SOD and CAT activities declined markedly from September with the drop of temperature In contrast, in alive roots, MDA content increased markedly from September 1 to September 15,and then decreased to early October and was litter fluctuated from early Oct to December, also during spring Average activities of SOD, CAT, POD in roots of all species increased 170%, 130%, and 56%, respectively from September to early November Thereafter these enzymatic activities declined throughout winter, but still higher than that of September, and elevated again with rising of temperature from mid April to early May These results provided evidence for the ability of the alpine plant root to activate enzymatic defense mechanisms to limit the production of free radicals to protect membrane integrity In dead leaves, it is because antioxidant enzymes inactivated lead to accumulation of AOS initiating lipid peroxidation APX is not important scavengers for this study Freezing tolerance in alpine grasses correlated with an increased capacity to scavenge or detoxify activated AOS by antioxidant enzymatic system