不同种群羊草幼苗保护酶系统对干旱的反应及其生理生态适应

用聚乙二醇(PEG6000)对内蒙古不同生境3个羊草种群(阿巴嘎、白音锡勒、嘎松山)进行了渗透胁迫(-0．5MPa—1．0MPa)试验，对15d中叶片含水量、游离脯氨酸积累、几种保护酶(SOD、POD、CAT)的活性及MDA含量的动态变化过程进行了测定。结果表明，各种群羊草对轻度胁迫(-0．5MPa)反应不敏感，叶片含水量、脯氨酸积累及几种酶活性与对照差异不显著；随胁迫强度增大和胁迫时间的延长，叶片相对含水量下降，脯氨酸大量积累；脯氨酸积累与叶片含水量呈显著负相关(r=-0．7161)。几种保护酶活性在干旱处理期间均表现为双峰曲线，-0．5MPa胁迫下酶活性变化幅度较小，不同地理种群羊草酶活性最高值及上升到最高值的处理时间之间存在着一定差异。嘎松山种群的SOD和CAT活性上升快，但后期活性较低，3种酶活性最高值均大于其它两个种群；阿巴嘎种群酶活性最高值出现时间晚，后期维持较高的酶活性。胁迫条件下SOD和CAT活性与MDA含量成正相关，POD活性与MDA含量无显著相关性。渗透胁迫下阿巴嘎种群叶片含水量下降少、脯氨酸积累速度慢、胁迫后期维持较高酶活性、膜脂过氧化作用较小，其抗旱性强于其它两个种群；嘎松山种群叶片含水量下降多、脯氨酸积累量大、胁迫前期保护酶活性上升快，后期酶活性较低、膜脂过氧化作用较强。不同种群羊草的耐旱机制可能存在差异，而保护酶系统的调节是其对生态环境适应的重要生理反应。

Responses of Protective Enzyme System of Leymus Chinensis Populations from Differently Geographic Areas to Osmotic Stress and Their Physio - Ecological Adaptability

Leymus chinensis from different geographic locations (Abaga League, Baiyinxile Farm, Gasong Mountain) of the Inner Mongolian Plateau were treated with osmotic stress solution PEG 6000(- 0.5 MPa, - 1.0 MPa). The leaf water content (LWC), free proline content, activities of several defense enzymes and MDA content were measured at different times after treatments. We found that LWC, free proline content, enzyme activities and MDA content of the stressed plants were not significantly different from the control (CK) under - 0.5MPa osmotic stress; while LWC decreased, free proline content increased remarkably with increased stress levels and stress duration. Under osmotic stress, there were negative correlations between the accumulation of free proline and LWC (r=- 0.7161* * ). Activities of each of several protective enzymes showed two peaks in the stress period with the higher peak value under - 1.0 MPa. The peak values of the enzyme activities and the days reaching them after treatment differed between different geographic populations of Leymus chinensis. The SOD and CAT activities of Gasong Mountain population increased quickly in the early stages, with a peak on the fourth day, then decreased to that of original state in the later stages, and had the highest peak values of the three enzyme activities; the enzyme activities for Abaga population of Leymus chinensis reached its peak later and kept at higher level. The increase in activities of SOD and CAT were positively related to the increase of MDA under stresses, but the correlation between POD activity and MDA content was not significant. The Abaga population had a smaller decrease of LWC and slower accumulation of free proline in leaf, maintained higher level of protective enzyme activities at the later stages with lower degree of lipid peroxidation than the other two populations. The Gasong Mountain population had a sharper decrease in LWC and higher accumulation of free proline in leaf, while its defense enzyme activities increased quickly in the early stages and kept at lower level in the later stages with more lipid peroxidation. It may be suggested that the protective enzymes play a key role under drought condition and there be more than one mechanism for different populations of Leymus chinensis to acclimate to drought stress.