Abstract: In order to reveal the stomatal response of Alfalfa under water stress,leaf water potential,transpiration rate(T_r),stomatal conductance(G_s) of alfalfa(Medicago sativa) and their relationship under water stress are studied by adopting pot-cultivation designs.Results show that the leaf water potential,T_r and G_s of alfalfa decreased with water stress increasing.The daily change of the leaf potential,Trand G_s display a bimodal curve pattern with the same mean value.The maximum is obtained under full water supply,followed by light water stress,moderate water stress and severe water stress.The lowest leaf water potential decreases with the decreasing of soil moisture,the peak appearing time of leaf potential and Trunder moderate and severe water stress is earlier than that of full water supply and light water stress.Under moderate and severe water stress,when the water potential was-4.68 MPa,or T_r was 3.27 g·m^-2·h^-1,the stomata begin to close.Under full water supply and light water stress,Tr increases with the decreasing water potential,and Gs increases with the increasing of T_r.The leaf water potential changes not only related with the soil moisture,but also closely related with the leaf development.

Key words: Medicago sativa, Water stress, Leaf water potential, Transpiration rate, Stomatal conductance

摘要： 采用盆栽水分试验,研究了不同土壤水分条件下紫花苜蓿(Medicago sativa)叶水势、蒸腾速率和气孔导度的变化规律及相互关系,以期揭示其对土壤水分胁迫的气孔响应机制。结果表明:苜蓿叶水势、蒸腾速率(T_r)、气孔导度(G_s)均随水分胁迫加剧而降低,三者日变化均呈双峰曲线特征,日平均值表现为充分供水>轻度胁迫>中度胁迫>重度胁迫。最低叶水势随土壤水分降低而降低;在中度和重度胁迫下,叶水势和蒸腾速率日变化峰值出现的时间提前,当叶水势为-4.68 MPa或T_r为3.27 g·m^-2·h^-1时,气孔开始关闭;在充分供水和轻度胁迫下,T_r越高,叶水势越低,且G_s随着T_r增加而增加。叶水势的变化除受土壤水分影响外,还与叶片生长发育密切相关。

关键词: 紫花苜蓿, 水分胁迫, 叶水势, 蒸腾速率, 气孔导度