中文摘要：

紫花苜蓿（Medicago sativa L.）作为世界农牧业发展中一种极为重要的豆科牧草,具有较强的抗旱性,但干旱仍是制约紫花苜蓿生产的主要逆境因子。近年来,温室效应不断加强,全球温度也逐年持续升高,对农作物及牧草的干热研究也就显得极为重要。以云南红河州建水县的6个栽培紫花苜蓿资源为材料,在自然干热条件下研究其光合特性及生理响应。结果表明：24号紫花苜蓿资源的净光合速率显著高于其他紫花苜蓿资源（P〈0.05）,14号和15号紫花苜蓿资源的蒸腾速率显著高于其他紫花苜蓿资源（P〈0.05）,16号和15号紫花苜蓿资源的气孔导度显著高于其他苜蓿资源（P〈0.05）,24号和14号的紫花苜蓿资源的胞间二氧化碳浓度显著高于其他紫花苜蓿资源（P〈0.05）。净光合速率与光合有效辐射、蒸腾速率、胞间CO2浓度呈正相关,而与气孔导度呈负相关。

英文摘要：

Alfalfa（Medicago sativa L.） is very important forage in the development of farming and live stock industry in the world.Alfalfa has strong tolerance to drought,but drought is the mainly adversity factor to restrict alfalfa production.In recent years,greenhouse effect is continuously strengthening,and global temperature becomes warm,so it is very important to study crops and pasture tolerance to drought and heat.Six alfalfa were cultivated in the Jianshui County,Honghe,Yunnan Province and their photosynthetic characteristics and response to dry-hot environment were studied.The results showed that net photosynthetic rate of alfalfa No.24 was significantly higher than those of other alfalfa（P〈0.05）.The transpiration rates of alfalfa No.14 and No.15 were significantly higher than those of other alfalfa（P〈0.05）.The stomatal conductances of alfalfa No.15 and No.16 were significantly higher than those of other alfalfa（P〈0.05）.The Internal CO2 of alfalfa No.14 and No.24 were significantly higher than those of other alfalfa（P〈0.05）.Net photosynthetic rate was positively correlated with photosynthetic active radiation,transpiration rate,intercellular CO2 concentration,but it was negatively correlated with stomatal conductance.