【作者】 王虹；

【导师】 喻景权；

【作者基本信息】 浙江大学 ， 蔬菜学， 2009， 博士

【摘要】 设施栽培业已成为我国现代农业中的重要组成部分，然而由于弱光及病害的频繁发生，严重影响了蔬菜作物的生长，成为我国设施农业可持续发展的瓶颈问题。因此，探明不同光质对蔬菜生产及病害的影响机制、筛选高效的人工光源，是现阶段可持续设施农业亟待解决的重要问题。本文以黄瓜（Cucumis sativus L）为试材，研究了不同光质对黄瓜幼苗CO₂同化、叶绿素合成、叶片衰老及其在人工补光中的作用等方面的影响，并研究了其缓解黄瓜白粉病发生的生理分子机制。所取得的主要结果如下：1．研究了不同光质（紫光、蓝光、绿光、黄光和红光）对黄瓜光合作用的调节机理。结果表明，与对照的白光相比，不同单波光质导致了植株生长减慢、净光合速率（Pn）、PSⅡ光化学相对量子效率（ΦPSⅡ）的下降，这些参数的变化在绿光、黄光和红光的处理中表现尤为明显。但是紫光和蓝光处理后，植株的气孔导度（Gs）、Rubisco总活性和初始活性显著增加，卡尔文循环相关基因大量表达以及可溶性糖、蔗糖及淀粉等碳水化合物累积，而绿光、黄光和红光的处理则呈现相反的趋势。不同光质下的Pn变化与光合色素的吸收光谱相一致。紫光和蓝光所引起的Pn降低可能与光系统能量分配的失调有关，除此之外，绿光、黄光和红光所引起的Pn降低还与Gs下降、卡尔文循环基因表达量下调有关。2．研究了不同光质（紫光、蓝光、绿光、黄光和红光）对黄瓜幼苗叶绿素合成的影响。结果表明，红光和蓝光促进了叶绿素的合成，紫光和蓝光促进了类胡萝卜素的合成，绿光、黄光则抑制了叶绿素及类胡萝卜素的合成。此外，紫光、蓝光和红光上调了GluTR、MgCH及FeCH等叶绿素合成相关基因的表达，下调了POR的表达。而绿光和黄光则呈现相反的趋势。以上的结果表明紫光、蓝光和红光在植物叶绿素合成过程中起作用。3．研究了不同光质（紫光、蓝光、绿光、黄光和红光）的补光效率及其提高黄瓜叶片光合作用的生理分子机制。结果表明：紫光、蓝光、红光和白光处理能增加植株的光合作用，提高光合作用相关基因的表达。绿光和黄光则呈现相反趋势。在多波长的试验中，进一步表明了绿光对光合作用的限制作用，即绿光限制了蓝光和红光对光合作用及相关基因的促进作用。此外，红蓝组合显著的提高了植株光合作用及相关基因的表达，其作用效果要好于白光处理，补光效率较高。单波补光处理6h后，我们发现不同光质补光所引起的光合作用相关基因表达的改变伴随着GSH和AsA氧化还原状态的改变，因此我们推测，其在不同光质调节的光合作用相关基因的表达中起作用。4．研究了不同光质（紫光、蓝光、绿光、黄光和红光）对黄瓜叶片衰老的作用及其机制。结果表明，与白光相比，紫光和蓝光诱导了抗氧化酶基因的表达及活性的上升，延缓了叶绿素和可溶性蛋白含量的下降，并且使MDA的含量保持相对较低的水平，从而延缓了植株的衰老。绿光、黄光和红光则抑制了抗氧化酶的活性，导致黄瓜植株叶绿素和可溶性蛋白含量的不断下降及MDA含量的持续上升，加速了植株的衰老进程。5．研究了不同光质（紫光、蓝光、绿光、黄光和红光）对黄瓜白粉病发生的调控机理。结果表明，与白光相比，红光显著提高了植株中自由态水杨酸的含量、H₂O₂含量及包括WRKY、PR在内的抗病相关基因的表达，从而提高了植株的抗性，抑制了病原菌的侵染。另外，紫光和蓝光虽不能降低植株的发病率，却能增加植株中苯丙氨酸解氨酶、多酚氧化酶的活性及总酚和类黄酮的含量。处理10 d后，与对照的白光相比，红光处理显著降低了植株的病害发生率，其它单波光质则导致了病害的普遍发生。这些结果表明，红光诱导的黄瓜叶片对白粉病的抗性与水杨酸诱导的信号传导途径密切相关。更多还原

【Abstract】 Greenhouse horticulture is an important integrative part of modern agriculture,however,vegetable development are severely affected by low light and pathogeninfection.Hence,there is a growing emphasis on understanding the mechanism oflight quality on vegetable growth and pathogen infection,and selecting alternativesartificial lights in modem vegetable industry.In this study,we investigated changes ofCO₂ assimilation,chlorophyll biosynthesis,senescence and supplemental lighting,aswell as incidence of powdery milder and associated metabolism in cucumber plants inresponse to different wavelength lights.The results are as follows:1.We examined how light quality influences plant photosynthesis by analyzingchanges in photosynthetic parameters and expression levels of some photosynthesisrelated genes of cucumber（Cucumis sativus L.cv.Jinyou No.1）plants.The resultsshowed that all plants grown under monochromatic light had reduced growth,CO₂assimilation rate（Pn）and quantum yield of PSII electron transport(φ_psⅡ)ascompared with plants grown under W,and these reductions were more significant inthe plants under G,Y and R.Interestingly,P-and B-grown plants had higher stomatalconductance（Gs）,total and initial Rubisco activities and higher transcriptional levelsof 10 genes which encode key enzymes in the Calvin cycle together with higher totalsoluble sugars,sucrose and starch contents as compared with W-grown plants,whereas in G-,Y-,and R-grown plants these parameters declined.Therefore,thereduction in Pn under P and B is likely the result of inactivation of photosystems,while under Y,G and R,the reduction is attributed to both photosystem inactivationand the closure of stomata and the transcriptional down-regulation of genes for theCalvin cycle enzymes.In conclusion,light quality alters plant photosynthesis by theeffects on the activity of photosynthetic apparatus in leaves and the effects on thegene expression and/or activity of the Calvin cycle enzymes.2.We investigated the effects of different light qualities on chlorophyll biosynthesis in five-day-old etiolated cucumber seedlings.Exposure to R and Bresulted in an increased content of chlorophyll,and P and B enhanced the content ofcarotenoid,whilst G and Y decreased both contents of chlorophyll and carotenoid.Furthermore,P,B and R up-regulated the transcriptional levels of GluTR,MgCH andFeCH,and down-regulated the expression of POR,whereas G and Y showed theopposite results.3.We investigated the efficiency of supplemental lights with different lightsources on the physiological and photosynthetic characteristics and its molecularmechanisms in cucumber seedling.The results showed that all plants grown under B,R and W increased the CO₂ assimilation rate（Pn）and transcriptional levels of 10genes which encode photosynthesis,whereas in G-and Y-grown plants theseparameters declined.In multiwavelength experiment,G decreased the effects of B andR on increasing the photosynthesis.Furthermore,the combination of B and R hadsignificantly increased Pn and up-regulated the expressions of genes encodingphotosynthesis,and its effect was more significant than that of W.Interestingly,wefound that the changes of transcriptional levels of photosynthesis related genes causedby different light qualities were companied with the changes of redox status of GSHand AsA.Therefore,we proposed that redox may be involved in the processes whichlight qualities act on4.The role of different light qualities in leaf senescence was investigated incucumber seedlings.P and B increased the transcript levels and activities ofantioxidant enzymes and delayed the decreases in the contents of chlorophyll andsoluble proteins,therefore,maintaining the lower content of MDA and preventingsenescence.However,G,Y and R accelerated plant senescence by inhibiting theactivities of antioxidant enzymes and leading to the decreases in the contents ofchlorophyll and soluble proteins and the increase in the content of MDA.Theseresults indicate that P and B prevented senescence by maintaining high levels ofantioxidant enzymes.6.To determine whether light quality affects the incidence of disease,cucumberplants were exposed to purple（P）,blue（B）,green（G）,yellow（Y）,red（R）and white （W）light with or without the inoculation of Sphaerotheca fuliginea for 72 h.Exposure to R resulted in an increased level of free salicylic acid（SA）together withincreased expression of defense genes such as PR-1 and H₂O₂ accumulation ascompared with plants exposure to W or other monochromatic lights.In comparison,plants grown under P and B exhibited higher activities of phenylalanineammonia-lyase and polyphenoloxidase together with increased level of flavonoids.Notably,red light increased whilst other monochromatic lights decreased theresistance to Sphaerotheca fuliginea as compared to W.Our findings highlight theimportance of red light in the light-induced resistance and the importance ofSA-dependent signalling pathway in the red-induced tolerance.更多还原