中文摘要：

利用抗旱性不同的32个棉花品种,通过田间苗期水分胁迫,测定了与抗旱性有关的游离脯氨酸、叶绿素、甜菜碱、丙二醛（MDA）的含量和保护性酶活性的变化等生理生化指标。结果表明,苗期水分胁迫增加了游离脯氨酸、甜菜碱、MDA、可溶性糖含量,提高了超氧化物歧化酶（SOD）、过氧化物酶（POD）的活性,减少了叶绿素的含量,但各品种间的应对机制各有差异。通过主成分分析,将32个品种的7个相互关联的单项指标综合成为3个独立的综合指标,并通过聚类分析,将32个品种划分为2大类,第Ⅰ大类可分为两个亚类,第1亚类中的鸡爪棉属于高度抗旱型;第2亚类中的奎85-174等17个品种属中度抗旱类型;第Ⅱ大类也可分为两个亚类,第4亚类的新海20等8个品种属于高度不抗旱型,其余6个品种属于不抗旱型。通过主成分分析和聚类分析,对32个棉花品种苗期抗旱性进行的分类和评价结果表明,胁迫条件下脯氨酸含量、甜菜碱含量、可溶性糖含量、MDA含量、叶绿素含量、SOD活性和POD活性均可作为棉花苗期抗旱性鉴定指标,利用此7项值建立的D值抗旱评价体系对棉花品种苗期抗旱性的解释率为34.49%。

英文摘要：

Thirty two cotton cultivars with different drought resistance were used to determine contents of free proline,chlorophyll,betaine,malondialdehyde（MDA） and the changes of protective enzyme connected with drought resistance by water stress at the seedlings stage in the field.Results show that water stress of seedlings stage increases the contents of free proline,betaine,malondialdehyde（MDA） and soluble sugar,raises the activity of SOD and POD,reduces the content of chlorophyll,but every variety has different coping mechanisms.By principal component analysis,7 interrelated single indicator of 32 varieties are integrated into three separate compositive indicators,and 32 varieties are divided into two major categories through cluster analysis,category Ⅰ divided into two subclasses,Jizhuamian belonged to high drought resistance type in subclass 1;In subclass 2,seventeen varieties such as the Kui 85-174 belonged to middle drought resistance type;Category Ⅱ can be divided into two subclass,in fourth sub-category eight varieties such as Xinhai 20 are highly no drought resistance type,and the remaining six varieties belong to notdrought resistance type.This study was conducted to classify and evaluate the 32 cotton cultivars at the seedlings stage by the means of principal component analysis and cluster analysis,results show that contents of free proline,chlorophyll,betaine,malondialdehyde（MDA） and the changes of protective enzyme under water stress all can be used as the indicators of drought-resistance identification at the seedlings stage of cotton,D value of the drought-resistance assessment system are established by above 7 indicators,whose explaining efficiency is 34.49% of the drought-resistance identification at the seedlings stage of cotton.