高温胁迫下不同耐热性切花菊光化学活性和能量分配差异

The difference of photochemical activity and energy distribution on cut chrysanthemum varieties with different heat tolerance under high temperature stress

为探究高温胁迫对切花菊叶片光合作用及PSⅡ和PSⅠ功能的影响,本研究对‘威尼斯’(耐热型品种)、‘紫精灵’(中等耐热型品种)、‘凯撒红’(热敏感型品种)3个耐热性不同的品种45℃处理12 h,研究高温胁迫对切花菊生长、光合参数、光合机构中光合电子传递链的运转情况以及光合作用相关基因的影响。结果显示,高温胁迫下‘威尼斯’植株仍保持挺立,而‘凯撒红’严重萎蔫,叶片保水能力较差。高温胁迫下‘威尼斯’、‘紫精灵’和‘凯撒红’Pn分别比对照下降了37.31%、114.92%、104.34%,表明在高温胁迫下光合作用能力下降。3种切花菊的OK、OJ相的荧光差异动力学均显示出正L-band和正K-band,表明放氧复合体活性抑制,PSⅡ单位能量连接下调,PSⅡ天线结构被破坏,是造成高温胁迫下光合作用降低的原因之一。高温胁迫下‘威尼斯’通过保持高水平的PSⅡ最大光化学效率(φPo)、将电子传递到电子传递链初级醌受体(QA)下游的其他电子受体概率(ψEo)和低水平的热耗散量子比率(φDo),使更多的能量被PSⅡ反应中心捕获并进入电子传递链,可利用的光化学反应能量多于‘紫精灵’和‘凯撒红’。此外,高温胁迫下,‘威尼斯’捕获的能量传递到电子链末端的量子产率(δRo)降低,表明更多的PSⅠ参与环式电子传递,PSⅠ的活性(ΔI/Io)提高;同时,‘威尼斯’在高温胁迫下可保持较高的Cmrbc L、Cmpsb A、Cmpsa A和Cmpsa B基因表达水平,减轻光抑制,增强光合作用,从而具有更好的耐热性。本研究系统地阐明了高温胁迫下不同耐热性切花菊光化学活性和能量分配差异,表明耐热性不同的切花菊品种有着不同的热胁迫保护机制,为耐热切花菊品种的选育提供理论依据。

In order to explore the effects of high temperature stress on photosynthesis,PSⅡand PSⅠfunctions of cut chrysanthemums leaves,three cut chrysanthemums with different heat resistance,such as‘Weinisi’(heat-resistant variety),‘Zijingling’(medium heat-resistant variety)and‘Kaisahong’(heat-sensitive variety),were treated at 45℃for 12 h.The effects of high temperature stress on growth,photosynthetic parameters,operation of photosynthetic electron transport chain in photosynthetic apparatus,photosynthetic related genes of cut flower chrysanthemum were studied.The results showed that the‘Weinisi’remained upright under high temperature stress,while the‘Kaisahong’were severely weakened,the water retention capacity of the blade is poor.Under high temperature stress,P_n of the‘Weinisi’,‘Zijingling’and‘Kaisahong’decreased by 37.31%,114.92%and 104.34%,respectively,compared with the control,it showed that the photosynthetic capacity decreased under high temperature stress.The differential fluorescence kinetics of OK and OJ phases showed positive L-band and positive K-band in different varieties under high temperature stress,indicating that the activity of oxygen-evolving-complex was inhibited,the connection of PSⅡunit energy was down,and PSⅡantenna structure was damaged,which was one of the reasons for the decreased photosynthesis under high temperature stress.Under high temperature stress,‘Weinisi’had more photochemical energy available than‘Zijingling’or‘Kaisahong’,because more energy was captured by the PSⅡreaction center and entered the electron transport chain through maintaining a high level of maximum quantum yield for primary photochemistry(φ_(Po)),Probability that an electron moves further than Q_A~-(ψ_(Eo)),and a low level of the quantum yield of energy dissipation(φ_(Do)).In addition,under high temperature stress,the efficiency with which an electron from the intersystem electron carriers is transferred to reduce end electron acceptors at the PSⅠacceptor side(δ_(Ro))was decreased and the activity of PSⅠin‘Weinisi’,indicating that more PSⅠparticipated in cyclic electron transport.Meanwhile,the expression levels of Cmrbc L,Cmpsb A,Cmpsa A and Cmpsa B genes could be maintained to reduce photoinhibition,enhance photosynthesis,and thus‘Weinisi’had better heat resistance.This study systematically elucidated the differences of photochemical activity and energy distribution of different heat resistant cut chrysanthemums under high temperature stress,indicating that different heat resistant cut chrysanthemums varieties have different heat stress protection mechanisms,which provides a theoretical basis for the breeding.