【摘要】 采用室内人工模拟低温逆境的方法,研究硝普钠（SNP,NO供体）预处理对低温（昼10℃/夜6℃）胁迫下冷敏感品种‘津研四号’和较耐冷品种‘津优一号’黄瓜（Cucumis sativus）幼苗叶片快速叶绿素荧光动力学曲线及叶绿素荧光参数的影响,探讨了NO对低温胁迫下黄瓜叶片光系统Ⅱ（PSⅡ）原初光化学反应的保护效应,为低温下NO保护黄瓜PSⅡ原初光化学反应的作用机理提供理论依据。结果表明:与‘津研四号’相比,低温对‘津优一号’放氧复合体（OEC）的损伤程度、次级电子受体Q_A的还原速率及电子传递效率的抑制作用更小;NO显著提高了低温胁迫下两品种黄瓜幼苗的最大光化学效率（F_v/F_m）、实际光化学效率(Y_Ⅱ)、光合电子传递速率（ETR）、光化学淬灭系数（q_P）,显著降低了PSⅡ Q_A的氧化还原状态（1-q_P）,提高了反应中心捕获的电子传递到Q_A以后的效率（Ψ_o）、反应中心吸收的光能用于电子传递的量子产额(Ψ_Eo)、光系统I（PSI）末端电子受体的还原能力(Ψ_Ro)、反应中心密度（RC/CS_o）、PSⅡ叶绿素分子作为反应中心起作用的概率(γ_RC)、光合性能指数(PI_ABS),降低了单位反应中心的光能吸收（ABS/RC）、单位反应中心的热能量耗散（DI_o/RC）、反应中心最大关闭速率（M_o）、单位反应中心的能量传递（ET_o/RC）、K相占J相的相对可变荧光（W_k）及低温24 h后‘津优一号’的J相可变荧光（V_j）、I相可变荧光（V_i）。说明低温胁迫下,外源NO能够有效保护黄瓜幼苗OEC,提高Q_A向次级电子受体Q_B的电子传递速率及质体醌（PQ）接受电子的能力,使Q_A快速进入氧化状态,促进电子传递顺利进行,且NO对‘津优一号’的作用更为显著。更多还原

【Abstract】 The effect of sodium nitroprusside（SNP,a donor of NO）pretreatment on rapid chlorophyll fluorescence kinetic curves and chlorophyll fluorescence parameters of cucumber（Cucumis sativus）cold-sensitive cultivar‘Jinyan No.4’and cold-tolerant cultivar‘Jingyou No.1’seedlings under chilling（10℃/6℃,day/night）stress was studied.The protective effect of nitric oxide（NO）on the primary photochemical reaction of photosystem Ⅱ（PSⅡ）in cucumber leaves under chilling stress was discussed,providing a theoretical basis for the mechanism of NO protecting PSⅡ primary photochemical reaction of cucumber at chilling stress.The results show that compare to‘Jinyan No.4’,there is less inhibition on the degree of damage of oxygen decomposition complex（OEC）,the reduction rate of secondary electron acceptor Q_A and the inhibition of electron transport efficiency on‘Jinyou No.1’.Pretreating with SNP of cucumber before chilling stress could significantly increase maximal photochemical efficiency（F_v/F_m）,actual photochemical efficiency(Y_Ⅱ),photosynthetic electron transport rate（ETR）and photochemical quenching coefficient（q_P）,significantly reduced the redox state of Q_A（1-q_P）,improved probability that a trapped exciton moves an electron into the electron transport chain beyond Q_A（Ψ_o）,quantum yield for electron transport from Q_A to plastoquinone(Ψ_Eo),quantum yield for reduction of end electron acceptors at the PSI acceptor side(Ψ_Ro),density of active PSⅡ reaction centers（RC/CS_o）,probability that PSⅡ chlorophyll molecule functions as RC(γ_RC)and performance index of PSⅡ based on absorption(PI_ABS),and reduced absorption flux per RC corresponding directly to its apparent antenna size-ratio between chlorophyll in antenna and chlorophyll in RC（ABS/RC）,dissipated energy flux per RC at the initial moment of the measurement（DI_o/RC）,approximated initial slope of the fluorescent transient（M_o）,electron transport flux from Q_A to plastoquinone per RC（ET_o/RC）,K-phase accounts for the relative variable fluorescence of J-phase（W_k）and relatively variable fluorescence of J-phase（V_j）and I-phase（V_i）of‘Jinyou No.1’under chilling stress for 24h.It indicates that exogenous NO can effectively protect the oxygen release complex（OEC）in cucumber seedlings,and improve the electron transfer rate of Q_A to Q_B and the ability of plastoquinone to accept electrons.In consequence,Q_A can quickly enter the oxidation state and promote the smooth transfer of electrons.The effect of NO on‘Jinyou No.1’is more significant.更多还原