【作者】 段伟；

【导师】 孟庆伟； 米华玲；

【作者基本信息】 山东农业大学 ， 植物学， 2004， 博士

【摘要】 本文以冷敏感植物黄瓜津研 4 号(Cucumis sativus L.)为材料,研究了低温弱光胁迫对 PSI 和 PSII 光抑制及其相互关系的影响。以烟草(Nicotiana tabacum c.v. Xanthi)ndh 基因缺失突变体为试材,探讨了低温弱光胁迫下叶绿体 NAD(P)H 脱氢酶复合体(NDH)介导的 PSI 循环电子传递的功能以及 NDH 复合体对不同光质的响应。此外,初步探讨了硫灯和氙灯下黄瓜幼苗生长差异与植物内源激素的关系。主要结果如下:1. 低温弱光胁迫下黄瓜叶片的光合作用、光抑制及其保护机制 低温降低了黄瓜叶圆片的光合速率,在光合速率和气孔导度降低的同时,胞间 CO2浓度升高,羧化效率降低,说明低温弱光胁迫下光合速率的降低主要是由非气孔因素引起的。与暗处低温胁迫相比,在低温弱光胁迫下黄瓜叶片光合放氧速率下降更明显。 黄瓜类囊体膜电子传递速率显示,PSII、PSI 以及整个电子传递活性在低温弱光处理过程中呈下降趋势。在低温弱光和低温暗处理下 PSII 的活性均降低,比处理前分别下降了 30.8%和 27.7%。在低温弱光下处理 6h 后黄瓜叶片 PSI 的电子传递活性降低 44.2%,而在低温暗处理下其活性仅降低 14.9%。总电子传递活性在低温弱光和低温暗处理下分别降低 30.1%和 17.4%。这表明低温弱光胁迫导致黄瓜 PSI 更严重的光抑制。 低温胁迫对叶绿素荧光参数的影响。低温弱光处理降低黄瓜叶片的最大光化学效率 1<WP=11>段伟:低温条件下叶绿体 NAD(P)H 脱氢酶复合体的生理功能及其对光质的响应(Fv/Fm),但变化不明显。低温弱光胁迫导致 PSII 实际光化学效率(ΦPSII)和光化学猝灭参数(qP)明显降低, 而在低温暗处理下基本不变。低温弱光胁迫下非光化学促灭(NPQ)增加。说明即使在弱光下,由于低温抑制了黄瓜叶片的碳同化过程也会导致光能过剩,依赖叶黄素循环的非辐射能量耗散(NPQ)在低温弱光胁迫下具有光破坏防御功能。 低温弱光下黄瓜叶片抗坏血酸(AsA)含量下降,超氧化物歧化酶(SOD)和叶绿体抗坏血酸过氧化物酶(APX)活性降低,导致过氧化氢(H2O2)积累,从而引起黄瓜叶片的膜脂过氧化作用,表现为丙二醛(MDA)以及电解质外渗率的增加。2. 烟草 NDH 在低温弱光下的生理功能 在低温(4℃)弱光(100μmol m-2 s-1)胁迫 6h 后,野生型(WT)烟草和 ?ndhCJK突变体 P700 的氧化还原水平都有不同程度的降低,但 ?ndhCJK 的 P700 的氧化还原水平降低更明显,引入电子受体甲基紫精(MV)后,P700 的氧化还原恢复到处理前的水平,表明低温弱光胁迫引起烟草叶绿体间质成分的过度还原。PSII 最大光化学效率(Fv/Fm)及光合电子传递活性的变化表明低温弱光胁迫导致 ?ndhCJK 较为严重的 PSII光抑制,而 WT 和 ?ndhCJK 的 PSI 光抑制则较轻。非光化学猝灭(NPQ)的动力显示低温弱光主要抑制了?ndhCJK 突变体?pH的建立。此外,低温弱光胁迫下烟草?ndhCJK比 WT 产生更多的 H2O2。因此,推测低温弱光胁迫主要导致烟草叶绿体间质氧化还原成分的过度还原,从而限制了电子传递,导致活性氧产生。而 NDH 介导的 PSI 循环电子传递或叶绿体呼吸在低温弱光胁迫下减少活性氧的产生,从而具有光氧化破坏防御功能。 低温促进了 NDH 介导的 PSI 循环电子传递,这可能与低温增加了由 PSI 驱动的光依赖性的 NADPH 氧化活性有关。NDH 介导的 PSI 循环电子传递或叶绿体呼吸通过生成 ATP 为碳同化过程提供额外的能量,在低温下起光保护作用。3. 烟草ΔndhB 突变体对不同光质的响应及其适应 近红外辐射使 WT 的株高明显高于ΔndhB 突变体。在产生强近红外辐射的氙灯下生长的 WT 与生长在硫灯的 WT 相比,前者的作用光关闭后荧光上升相对速率(RFp)加快,峰值(Fp)增高。远红光关闭后的 P700+的暗还原初始速率也明显加快。Western 免疫印迹分析表明,氙灯下 WT 所含 NdhK 亚基的量明显比硫灯下的高。这说明近红外辐射 2<WP=12>山东农业大学博士论文促进 NDH 介导的 PSI 循环电子传递。此外,在近红外辐射下 WT 和ΔndhB 突变体叶片的光合特性无显著差异。4. 硫灯和氙灯下黄瓜幼苗生长的差异与植物内源激素的关系 为探索硫灯在农业生产中的应用前景,对硫灯和氙灯两种光源引起黄瓜幼苗生长差异的原因进行了初步探讨。与氙灯相比,硫灯照射下生长的黄瓜叶片单位面积叶绿素 a和 b 含量显著增加。但是,叶片的光合参数几乎没有差异。与氙灯相比,硫灯明显抑制了茎的伸长和干物质的积累,但是相对地促进了叶和根的生长。组织细胞观察显示,硫灯下生长的黄瓜幼苗的中胚轴表皮和皮层细胞纵向单位毫米长度的细胞数目比氙灯下的多。内源激素分析结果表明,与氙灯相比,硫灯下的黄瓜幼苗内源激素吲哚乙酸(IAA)、赤霉素(GA3)含量下降,而脱落酸(ABA)含量却明显增加。推测硫灯和氙灯下黄瓜幼苗生长的差异可能与内源激素的调控有关。更多还原

【Abstract】 Chilling-sensitive plant cucumber (Cucumis sativus L.), Jinyan No.4, was used as materialsto investigate the effects of chilling temperature (4℃) in the low light (100 μmol m-2 s-1) onphotoinhibition of photosystem I (PSI) and photosystem II (PSII) and their relationship inchilling-sensitive plants. Wild-type tobacco (Nicotiana tabacum c.v. Xanthi) (WT) and its amutant in which ndh genes were defected were used to study physiological function of cyclicelectron transport around PSI mediated by chloroplastic NAD(P)H dehydrogenase complex(NDH) upon exposure to chilling stress in the low light. Furthermore, primary investigationfor the relationship between growth difference and plant endogenous hormones of cucumberseedlings cultured under sulfur lamp or xenon lamp. The main results are as follows:1. Photosynthesis、photoinhibition and its protective mechanism of cucumber leavesduring chilling stress in the low lightPhotosynthetic rate decreased in cucumber leaf discs during chilling stress and decrease innet photosynthetic rate (Pn) and stomatal conductance (Gs) were accompanied by increase inintercellular CO2 concentration (Ci) and decrease in the carboxylation efficency (CE). Itsuggested that decrease of Pn caused by chilling temperature in the low light is mainly 4<WP=14>山东农业大学博士论文attributed to non-stomata factor. Net photosynthetic rate significantly decreased when leaveswere treated in the light compared to those in the dark. The results of elecreon transport rates in the cucumber thylakoikd indicated that electrontransport activities of PSII 、PSI and the whole electron chain had a descend trend. Theelectron transport activities of PSII were inhibited in the cucumber upon expouse to chillingstress in low light or in the dark, decreased by 30.8% and 27.7%, respectively. The electrontransport activities of PSI decreased by 44.2% after 6h chilling stress in the low light, and itonly decreased by 14.9% in the dark. The electron transport activities of the whole electrontransport chain decreased by 30.1% and 17.4% after chilling stress in the low light and in thedark, respectively. It suggested that chilling stress in the low light results in more severephotoinhibition of PSI compared to PSII and the whole electron transport chain. We analyzed effects of chilling stress on parameters of chlorophyll fluorescence incucumber leaves. After 6h chilling stress in the low light, Fv/Fm had little changes. ΦPSII andqP had a significant descend trend upon exposure to chilling stress in the low light, however,they changed little under chilling stress in the dark. NPQ increased markedly,implying that itresulted in excess excitation energy because chilling temperature inhibited CO2 assimilationin the cucumber leaves even in the low light. Dependent-xanthophyll cycle NPQ could protectplants from further photodamage under the chilling stress in the low light. In addition, chilling stress in the low light could cause the decrease of the contents of AsA ,activities of SOD in the cucumber leaves and activities of APX in the cucumber thylakoid,which in turn led to the accumulation of H2O2, and finally caused lipids peroxidation ofcucumber leaves, accompanied by the increase of MDA and electrolytic leakage.2. Physiological function of chloroplast NAD(P)H dehydrogenase of tobacco underchilling stress in the low light After expoused to chilling temperature(4℃) and weak light(100μmol m-2 s-1) for 6 h,far-red light (FR)-oxidizable P700 had a different degree of decrease in the WT and thetransformant plants of tobacco in which ndhCJK genes were insertionally inactivated(?ndhCJK). However, a lower far-red light (FR)-oxidizable P700 was found in ?ndhCJK 5<WP=15>段伟:低温条件下叶绿体 NAD(P)H 脱氢酶复合体的生理功能及其对光质的响应mutant than in WT. Since the lower FR-oxidizable P700 was almost recovered by addition ofelectron acceptor -methyl vio更多还原