作 者 ：韩瑞宏,卢欣石,高桂娟,杨秀娟
期 刊 ：生态学报 2007年 27卷 12期 页码：5229~5237
Keywords:alfalfa, drought stress, photosynthesis, physiological response,
摘 要 ：紫花苜蓿是重要的豆科牧草，具有较强的抗旱性，然而干旱仍是制约紫花苜蓿生产的主要逆境因子。通过盆栽试验，以抗旱性强弱不同的两种紫花苜蓿为试验材料，对干旱胁迫下紫花苜蓿的光合生理进行较为系统的研究，结果表明：（1）干旱胁迫下两种紫花苜蓿叶片净光合速率（Pn）、蒸腾速率(E)、气孔导度(Gs)、叶绿素含量(Chl)都有不同幅度的下降；叶绿体超微结构遭到破坏。相对于抗旱性弱的苜蓿，抗旱性强的苜蓿随干旱胁迫程度的加深，净光合速率下降较慢，叶绿体的外形及基粒结构受到的影响较小。（2）轻度干旱胁迫下气孔限制是两种紫花苜蓿Pn降低的主要因素，中度和重度干旱胁迫下非气孔限制是Pn降低的主要因素。（3）对叶绿素荧光参数的研究表明：干旱胁迫下两种紫花苜蓿PSⅡ反应中心光化学效率(Fv/Fm)、PSⅡ潜在活性(Fv/Fo)降低。总体上抗旱性强的紫花苜蓿Fv/Fm和Fv/Fo下降幅度小，PSⅡ利用光能的能力及PSⅡ的潜在活性均较强。PSⅡ光化学淬灭系数（qP）、非光化学淬灭系数（qN）的变化表现为干旱胁迫下两种紫花苜蓿qP值降低、qN值升高，总体上抗旱性强的紫花苜蓿qP降低的幅度低且qN升高幅度大，表明抗旱性强的紫花苜蓿PSⅡ反应中心电子传递活性受到的影响小，光合机构的损伤程度低。
Abstract:Alfalfa is an important legume forage with high drought resistance. However, drought stress is still the main adverse factor limiting alfalfa production. A pot-cultivation experiment was performed to investigate the photosynthetic physiology of alfalfa under drought stress. Two Alfalfas varying in their tolerance to drought were used, Longdong with high drought resistance and BL-02-329 with low drought resistance, to systematically study photosynthetic physiology under drought stress. The results showed: (1)Under drought stress, the net photosynthetic rate, transpiration rate, stomatal conductance and chlorophyll content decreased at varing extents, and chloroplast ultrastructure was damaged in the leaves of both Longdong and BL-02-329. Compared to the low drought-resistance BL-02-329, when subjected to drought stress, the net photosynthetic rate in the leaves of high drought-resistance alfalfa, Longdong, decreased more slowly and chloroplast shape and grana structure were less affected.(2)Stomatal restriction was the main factor for the P′n s decrease in the leaves of both alfalfas under light drought stress, while the non-stomatal restriction was the main factor for the P′n s decrease in the leaves of these alfalfas under medium and severe drought stresses.(3) Measurement of fluorescence of PSⅡ Reaction Center indicated Fv/Fm and Fv/Fo decreased in both alfalfas under drought stress. However, when under drought stress, Fv/Fm and Fv/Fo showed a smaller decrease, and the capability to utilize light and the potential to activate PSII remained higher in the high drought-resistance Longdong than in the low drought-resistance BL-02-329.Quenching（qP）of chlorophyll fluorescence decreased and Non-photochemical Quenching（qN）of chlorophyll fluorescence increased for both alfalfas under drought stress. Generally speaking, qP decreased less and qN increased more in the high drought-resistance alfalfa than in the low drought-resistance alfalfa, suggesting that when under drought stress, the electron transport activity and photosynthetic apparatus was damaged less in the alfalfa with high drought-resistance than in the alfalfa with low drought-resistance.
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