Cuticular wax, exposed at the outermost surface of plant organs, plays important roles in interactions of plant with environment and plays a critical role in plant drought tolerance by reducing cuticular water loss. In the experiment, two alfalfa (Medicago sativa) cultivars with different drought resistances, Aohan (high resistance) and Sanditi (low resistance), were selected to analyse the dynamics of leaf cuticular wax content and components, and the relationships between waxes and gas exchange indices under water deficit and high temperature stresses. The results showed that the alfalfa leaf surface was covered by thick wax platelets without specific orientations, which were constituted of alkanes (1.98-3.38％), primary alcohols (79.97-84.98％),esters (0.08-0.24％), and small amount of unknown constituents (7.77-13.38％). The wax deposition on alfalfa leaf was controlled by both variety type and environments. The wax content of Aohan was significantly higher than that of Sanditi. Under drought treatment, the proportions of alkanes in total wax increased (81.22-108.16％), that of primary alcohol decreased (3.23-12.54％);cuticular wax, photosynthetic rate (Pn), transpiration rate (Tr), and stomatal conductance (Gs) of Aohan changed insignificantly except for intercellular carbon dioxide (Ci), while those of Sanditi decreased significantly, indicating that cuticular wax might take part in the process of water metabolism and the alkanes in total waxes might play important role in controlling water loss. Under the conditions of high temperature, Pn, Tr, Gs, Ci, and leaf relative water content decreased significantly, water use efficiency (Pn/Tr) and proline content increased significantly in both cultivars; the total cuticular wax content unchanged in Aohan but significantly decreased in Sanditi, indicating that stomatal closure and osmotic adjustment were the main paths taken by alfalfa under severe stressed conditions.%选用2个抗旱性不同的紫花苜蓿品种,敖汉(强抗旱)和三得利(弱抗旱),在水热胁迫条件下,调查其叶表皮蜡质含量及组分变化规律、蜡质含量与气体交换参数、脯氨酸及叶片相对含水量之间的关系.结果表明,紫花苜蓿叶表皮存在致密的蜡质层,蜡质晶体结构呈片状,无特殊的晶格方向.叶表皮蜡质主要由烷(1.98%～3.38%)、醇(79.97%～84.98%)、酯类(0.08%～0.24%)及其他少量未知物质组成(7.77%～13.38%).品种类型、环境条件共同影响叶表皮蜡质的沉积.敖汉叶表皮蜡质含量显著高于三得利.水分胁迫后烷类比例增加(81.22%～108.16%),醇类比例下降(3.32%～12.54%),强抗旱品种叶表皮蜡质含量和气体交换参数无显著变化(除胞间二氧化碳浓度显著下降外),而弱抗旱品种蜡质含量和叶片光合速率、蒸腾速率、气孔导度及胞间二氧化碳浓度均显著下降.说明表皮蜡质限制水分散失,蜡质组分中烷类物质可能主要具限制水分散失的功能.高温及水热互作胁迫处理下,紫花苜蓿叶片光合速率和蒸腾速率下降,水分利用效率提高,叶片脯氨酸含量增加,相对含水量下降,敖汉蜡质含量下降,三得利蜡质含量无显著变化.表明在严重胁迫条件下紫花苜蓿主要通过关闭气孔和渗透调节来限制水分散失.
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