【作者】 周慧芬；

【导师】 郭延平；

【作者基本信息】 浙江大学 ， 果树学， 2003， 硕士

【摘要】 本试验以抗热性不同的两个柑橘品种：三年生枳砧温州蜜柑（Citrus unshiu Marc.）早宫川和脐橙（Citrus sinensis Osbeck.）朋娜盆栽苗为试验材料，在25℃的条件下预培养10 d后，仍以25±1℃下培养25 d为对照，另以38±2℃的环境下培养15 d，然后再在25±1℃下培养10 d作为高温胁迫和恢复处理，研究了高温胁迫对柑橘叶片光合机构运转的影响，以及植株本身的自我保护机理。在恢复阶段，我们对植株叶片喷以0.025 mol／L的抗坏血酸，观察了高温胁迫后它对柑橘植株恢复的效应。主要研究结果如下： 与对照相比，5d的短期高温胁迫使柑橘叶片Pn、Ci和Gs下降，气孔限制值L上升；随着高温胁迫时间的延长（5d以上），柑橘叶片的Pn和Gs进一步下降，同时Ci上升，L下降；而且测得的表观量子效率（AQY）、羧化效率（CE）、最大的光化学效率（Fv／Fm）、光化学猝灭系数（qP）、光系统Ⅱ的量子产量(Φ_PSⅡ)及CO₂同化的量子产量（ΦCO₂）下降，相反，不包括光下暗呼吸的CO₂补偿点（Γ^*）、光下的暗呼吸速率（Rd）、初始荧光（Fo）及非光化学猝灭系数（qN）上升；荧光动力学快速诱导曲线的O-P和I-P的斜率下降。在25±1℃下培养10d后，上述指标部分的或全部的恢复。这些结果表明，短期的高温胁迫导致的光合作用下降，是由气孔限制引起的；较长期的高温肋、迫（5d以上）使非气孔因素成为光合作用下降的主要原因。高温胁迫条件下，叶片的RuBPcase活性和RuBP再生速率降低使光合碳同化受到影响；同时叶片PSⅡ反应中心可逆失活或不可逆的破坏，减少PSⅡ开放的反应中心比例，抑制Q_A^-→Q_B的电子传递，减少参与CO₂固定的电子，增加了光能的热耗散；当然，还存在高温诱导的光合作用的光抑制。这些非气孔因素均成为限制光合作用的主要原因。 高温胁迫使柑橘叶片中的Φ_PSⅡ／Φ_CO2明显升高，超氧自由基产生速率的增加，并且与Chl a+b、Chl a和Chl b的下降，H₂O₂和MDA含量的上升，SOD、CAT、AsA-POD、G-POD和DHAR等酶活性的升高有极显著的相关性；虽然Pn和光呼吸速率（Pr）下降，但是Pr／Pn升高；在恢复阶段喷施AsA的植株叶片比喷水的植株叶片恢复的效果好。这表明，高温胁迫使柑橘叶片光氧化作用加强，活性氧产生增多，叶片的膜脂过氧化作用增加，可能是高温伤害光合机构的重要原因；而依赖于SOD、CAT、AsA-POD、G-POD和DHAR等酶的水—水循环的进行以及光合电子更多地流向光呼吸可能对缓解光合机构的光氧化伤害起着重要作用。外源的活性氧清除剂能够增强柑橘叶片活性氧的清除能力，从而加快光合机构光合功能的恢复。 品不D”。凡b较发现，高温胁迫后，脐橙叶 片的Pfl气Pf气AQY气C【九1’O飞卜V川111他卜个幅度及活性氧产生速率均比温州蜜柑低，抗氧化酶系统的活性比温州蜜柑高，WH为引涂胁迫10 d后上述指标也基本能恢复。这说明脐橙叶片的光合机构在高温胁迫一卜受到的仅去较轻，温州蜜柑在高温胁迫下受到的伤害较重，这反映了脐橙的耐高温能力强于温州蜜柑。更多还原

【Abstract】 Potted plants of two citrus varieties differing in high temperature resistivity (Citrus unshiu Marc. cv. zaogongchuan and Citrus sinensis Osbeck. cv. pcngna) were subjected to 25 1 (control) , 38 2 (high temperature stress), 800-1000 mol m-2 s-1 PPFD and 10 hours photoperiod during 15 days and recovered during 10 days at 25 1 at the same light regime, and were preconditioned at 25 1 for 10 days before the high temperature stress. At the recovery phase, we sprayed 0.025 mol/L AsA over the leaves of materials to look into the recovery effect of ascorbic acid (AsA) after high temperature stress. The effects of high temperature stress on the operation of photosynthetic apparatus and the protective mechanism in leaves of citrus plant were studied. The primary results are as follows:Compared with control, net photosynthetic rate (Pn), stomatal conductance (Gs) and intercellular CO2 concentration (Ci) declined, while stomatal limitation L increased under short-term high temperature stress of 5 days. Pn and Gs were further decreased, whereas Ci was increased and stomatal limitation L was decreased with time of high temperature stress is longer (more than 5 days). At the same time, apparent photosynthetic quantum yield (AQY), carboxylation efficiency (CE), light-saturating photosynthetic rate, CO2-saturating photosynthetic rate, photochemical efficiency (Fv/Fm), photochemical quenching (qP), quantum yield of PS 11 photochemistry ( pSII) and maximum quantum yield of CO2 assimilation ( CO2) as well as the slope of O-P and I-P in fluorescence induction kinetic curve declined. On the other hand, CO2 compensated point ex respiration in day ( ), respiration rate in day(Rd), minimal fluorescence intensity (Fo) and no- photochemical quenching (qN ) increased under high temperature stress. Recovery at 25 1 for 10 days, the date hereinbefore were recovered partly or completeness. This means that it was the stomatal limitation caused the decrease of photosynthesis under short-term high temperature stress and non-stomatal limitation was the main cause of the decrease of photosynthesis under long-term high temperature stress. In Citrus plant high temperature treatment, it were the decrease of activity of RuBPase and the regenerative rate of RuBP influence the photosynthetic carbon assimilation; photosystem reaction center was reversibly inactivated or irreversibly inhibited, the proportion of opened photosystem reaction was decreased, the electron translate of QA -QB was limited, the number of electron used to carbonfixation reduced, the photo energy dissipated by heat was increased; the photoinhibition induced by high temperature was exist. All this non-stomatal factors limited photosynthesis. ?At high temperature stress, O PSII/& co2 was elevated obviously, the rate of (V generated were increased, and it were correlated markedly with the decline of Chi a+b, Chi a and Chi b, correlated markedly with the increase of content of H2O2 and Malondialdehyde (MDA), and it have the remarkable correlation with the increase of activity of superoxide dismutase (SOD), Catalase (CAT), ascorbic acid peroxidase (AsA-POD), Guaiacol peroxidase (G-POD) and dehydroascorbate reductase (DHAR); the Pn and photorespiration rate (Pr) were declined, but Pr/Pn was raised; the plants sprayed with AsA have the more recovery compared with the plants sprayed with water in recovery phase. This means high temperature stress enhanced the photooxidation and increased the number of active oxygen, enhanced the lipid peroxidation in citrus plant, it was the important damage that high temperature to photosynthetic apparatus; the water-water cycle depended on SOD, CAT, AsA-POD, G-POD and DHAR and more photo electrons flowing to photorespiration were important to lighten the photooxidation in photosynthetic apparatus. Used of exogenous active oxygen scavengers can enhanced the ability to clear the active oxygens in citrus plant, quicken the recovery of pholosynthetic apparatus.Compared the two citrus varieties, we found that under high tem更多还原