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利用PEG-6000模拟水分胁迫(ψs=-0.2MPa,胁迫时间:48 h,复水48 h),研究了紫花苜蓿(Medicago sativa L)品种陇东苜蓿和阿尔冈金叶片叶绿素荧光特性和光合色素含量的变化,旨在探讨紫花苜蓿水分胁迫条件下的光合反应机制。结果表明:光化学淬灭系数(qP)和PSII线性电子传递的有效量子产额(YIELD)以及非光化学淬灭系数(qN)和表观光合电子传递效率(ETR)在胁迫前后随光合有效辐射(PAR)的变化规律分别可用公式:Y=aLn(X)+b(Y:qP或YIELD,X:PAR,X≠0)和Y=aX2+bX+c(Y:qN或ETR,X:PAR)来表示;在受到干旱胁迫后,PSII最大光能转化效率(Fv/Fm)、PSII潜在活性(Fv/Fo)和光合色素含量均明显低于对照,在任意光强下的qP、YIELD和ETR值也极显著低于对照的相应值,qN值则极显著高于对照的相应值;同时,和对照相比,qN和ETR光响应曲线顶点所对应的光强值在受到胁迫后亦明显下降,表明光抑制初始点的降低和最大光保护能力的减弱,甚至光抑制的提前到来。干旱胁迫使得PSII反应中心结构和功能遭到破坏而部分关闭,光合电子传递受阻,光能利用与光化学转化与能力下降,吸收的光能更多的以热能形式耗散。复水后,虽然有光保护机制的存在,但除陇东苜蓿光合色素含量及阿尔冈金类胡萝卜素外,各参数均未能恢复到对照水平,因此旱后复水不能完全解除干旱对PSII反应中心所带来的伤害。紫花苜蓿幼苗对干旱胁迫较为敏感。供试品种相比,陇东苜蓿耐旱性优于阿尔冈金。
The effects of PEG-6000 simulated water stress (ψs = -0.2MPa, stress time: 48 h, rewatering for 48 h) on chlorophyll fluorescence and photosynthetic pigments of alfalfa and algonquin varieties in alfalfa (Medicago sativa L.) Content changes, aimed to explore the alfalfa photosynthetic response mechanism under water stress conditions. The results showed that effective quantum yield (YIELD), non-photochemical quenching coefficient (qN) and apparent electron transport efficiency (ETR) of photochemical quenching coefficient (qP) and PSII linear electron transfer with photosynthetic active radiation PAR) can be expressed as Y = aLn (X) + b (Y: qP or YIELD, X: PAR, X ≠ 0) and Y = aX2 + bX + c ). Under drought stress, the maximum photosynthetic efficiency (Fv / Fm), PSII potential activity (Fv / Fo) and photosynthetic pigment content of PSII were significantly lower than that of the control. Under any light intensity, qP, YIELD and ETR values were also significantly lower than the corresponding values of the control, qN values were significantly higher than the corresponding value; at the same time, compared with the control, qN and ETR light response curve vertex corresponding light intensity values were significantly Decreased, indicating a decrease of the initial point of photoinhibition and a decrease of the maximum photoprotective ability, and even an early arrival of photoinhibition. Under drought stress, the structure and function of the PSII reaction center were partially destroyed by the destruction of the structure and function of the PSII reaction center, and the photosynthetic electron transport was blocked. The utilization of light energy and photochemical transformation decreased with the ability to absorb more light energy in the form of heat energy. After rewatering, although there was photoprotection mechanism, except for photosynthetic pigment content of Alfalfa in Eastern Gansu and Algonquin carotenoids, the parameters were unable to recover to the control level, so that the rewatering after drought could not completely relieve the drought on PSII The reaction center of the damage. Alfalfa seedlings are more sensitive to drought stress. Compared with the tested cultivars, the drought tolerance of alfalfa in eastern Gansu was better than that of Algonquin.