高温胁迫对草地早熟禾渗透势、膜脂肪酸成分及膜脂过氧化产物的影响

Heat Stress Effects on Osmotic Potential , Membrane Fatty Acid Composition and Lipid Peroxidation Content of Two Kentucky Bluegrass Cultivars Differing in Drought Tolerance

以‘Midnight’和‘Brilliant’两个草地早熟禾(Poapratensis)品种为试材,研究叶片渗透势、膜脂肪酸成分变化以及抗氧化酶对高温胁迫(35/30℃,昼/夜)的响应。高温胁迫下,‘Midnight’草地早熟禾草坪外观质量显著高于‘Brilliant’;随胁迫时间延长,‘Midnight’叶片的渗透势不断下降,而‘Brilliant’除在前5d有一定程度下降外,而后基本处于不变,‘Midnight’保持更高的相对含水量;两品种亚麻酸(18︰3)含量不断下降,亚油酸(18︰2)和棕榈酸(16︰0)不断增加,即脂肪酸饱和水平增加,‘Midnight’比‘Brilliant’含有更高的亚麻酸和棕榈油酸(16︰1),更低的棕榈酸和硬脂酸(18︰0),因而伴随着更高的双键指数(DBI);‘Brilliant’的MDA含量在胁迫10d后上升加快,胁迫25d结束时其含量为‘Midnight’的1.6倍,与之相对应的则是‘Midnight’的SOD酶活性显著高于‘Brilliant’,电解质渗透率显著低于‘Brilliant’。以上结果表明,‘Midnight’较强的渗透调节能力,较高的SOD酶活性,减轻了膜脂过氧化程度,有效保护了细胞膜稳定性,因而缓解了高温胁迫下的水分和氧化压力,表现出较强的耐热性。同时,‘Midnight’具有避免膜脂饱和程度剧烈变化的能力,也可能与耐热性较强有关。

The objective of this study was to examine osmotic potential, membrane fatty acid changes and antioxidant enzyme protection in two Kentucky bluegrass （Poa pratensis） cultivars （heat-tolerant ＇Midnight＇ and heat-sensitive ＇Brilliant＇ ） in response to heat stress （35/30 , day/night）. The results showed that under heat stress, ＇Midnight＇ demonstrated significantly higher turf apparent quality than ＇Brilliant＇ . With the extension of heat stress, osmotic potential in ＇Midnight＇ constantly decreased and remained unchanged in ＇Brilliant＇ except for an initial drop. At the same time, ＇Midnight＇ maintained a higher relative water content than ＇Brilliant＇. Linolenic acid （ 18 ： 3 ） content of the two cultivars gradually decreased and linoleic acid （ 18 ： 2） and palmic acid （ 16 ： 0） gradually increased, accordingly, there was an increase in levels of saturated fatty acid. However, the higher 18：3 and palmitoleic acid （16：1 ） contents, correspondingly, the lower 16 ： 0 and stearic acid （ 18 ： 0） contents in ＇Midnight＇ were observed as compared to ＇Brilliant＇, therefore, ＇Midnight＇ had a higher double bond index （DBI） than ＇Brilliant＇ . MDA content of ＇Brilliant＇ increased quickly after 10 d of heat stress and was 1.6 times higher than that of ＇Midnight＇ at the end of heat stress. Furthermore, SOD activity was significantly higher and electrolyte leakage was significantly lower in ＇Midnight＇ than in ＇Brilliant＇ . These results suggested that a better osmotic adjustment, a higher SOD activity and a less MDA accumulation from membrane unsaturated fatty acid composition in ＇Midnight＇ provided effective protection for membrane stability against heat stress. As a result, water deficit and oxidative stress was relieved. Meanwhile, ＇Midnight＇ had an ability to avoiding a dramatic change of lipid satration level. These mechanisms conferred ＇Midnight＇ a better heat tolerance compared to ＇Brilliant＇