紫花苜蓿越夏期的生理生化反应及评价

高温胁迫会致使植物发生一系列生理、生化及形态上的变化，为了研究在自然高温条件下不同紫花苜蓿（Medicago sativa）品种的生理生化变化情况，本研究选取22个紫花苜蓿品种，采用随机区组设计，测定在夏季高温期不同自然温度下叶片的相对含水量、相对电导率、可溶性蛋白含量、SOD和POD活性的动态变化，并通过聚类分析的方法，初步评价不同紫花苜蓿品种对夏季高温的耐受力，秋眠级与抗热性之间以及各评价指标之间的相关性。结果表明，1）随着温度由低－高－低的变化，相对含水量、可溶性蛋白含量、SOD和POD活性先升高后降低，叶片相对电导率逐渐上升，第4次样品平均相对电导率是第1次样品的3.36倍；2）通过层次聚类将参试品种对高温的耐受力分为3类，其中耐热类品种为赛特、德宝、皇冠、皇后2000、8925MF、金皇后和WL414，中等耐热品种为赛迪7号、南霸天、丰宝、WL 525HQ、阿尔冈金、猎人河、苜蓿王、牧歌401和四季旺，其余参试品种耐热性较差；3）相关性分析表明，秋眠级与相对含水量极显著负相关（P＜0.01），与可溶性蛋白含量和POD活性显著负相关（P＜0.05），与电导率和SOD活性之间相关系数为0.138和-0.405；测定5个生理生化指标之间呈现极显著相关关系。

Evaluation of physiological and biochemical response of alfalfa cultivars during summer

High temperature induces a series of responses in physiology and morphology. In order to study this changes, 22 alfalfa (Medicago sativa) varieties were used to measure the contents of relative water content, soluble protein, relative electrical conductivity, and the activity of superoxide dismutase and peroxidase under different natural temperature in the summer. A randomized complete block design was conducted with three replicates. Using the method of cluster analysis, the heat resistance of these varieties were preliminarily evaluated. The results showed that, 1) the four indicators except the relative electrical conductivity, increased as the temperature progressed from 25 May to 21 June, and then dropped as the temperature dropped. However, the relative electrical conductivity increased by 3.36 times gradually; 2) in this study, 22 alfalfa varieties were divided into three types by hierarchical clustering, which are strong heat resistance type, weak heat resistance varieties and intermediate type, respectively. The varieties of heat resistant type included Sitel, followed Derby, Phabulous, Empress 2000, 8925MF, Gold Empress and WL 414, while the intermediate heat resistant varieties were Sardi 7, Alfasuper, Powerplant, WL 525HQ, Algonquin, Hunter River, Alfking, AmeriGraze401 and Siriver. The other varieties were weak heat resistant varieties; 3) there was very significant negatively correlation (P<0.01) between FD class and relative water content. There were significant negatively correlations (P<0.05) between FD class and soluble protein content, and FD class and POD activity. The relationships between FD class and the conductivity or FD class and SOD activity were not significant (P>0.05). The correlation coefficient were 0.138 and -0.405. There were significant correlations among different indicators (P<0.01).