【作者】 郑荔敏；

【导师】 李延；

【作者基本信息】 福建农林大学 ， 植物营养学， 2009， 硕士

【摘要】 果园套种圆叶决明具有防止水土流失、提高土壤肥力、改善果园生态环境和促进果树生长、提高果实品质的作用。由于受果树遮荫的影响,圆叶决明存在明显生长不良的问题,已成为限制其推广应用的重要因素。本文从光合速率、叶绿素荧光参数、氮代谢、活性氧代谢等方面研究弱光胁迫对圆叶决明若干生理代谢的影响,旨在阐明弱光胁迫对圆叶决明生长发育影响的生理机制。主要结论如下:1从表征植株生长性状的株高、茎粗、叶片数、叶面积来看,CK(自然光)处理下生长最好,50%LI(50% light intensity即50%的自然光光照强度)、30%LI(30%光强)和10%LI(10%光强)处理与CK的差异均达极显著水平。说明弱光胁迫对圆叶决明的生长有明显的抑制作用,并且这种抑制作用随处理光强的减弱而提高。2弱光胁迫降低了圆叶决明叶片的光合色素含量。上位叶的Chla、Chlb含量以及Chla/Chlb下降,除50%LI处理的Chlb含量与CK差异不显著外,其余处理与CK差异均达显著或极显著水平;下位叶Chla、Chlb含量下降较CK差异均达极显著水平,Chla/Chlb虽有下降,但差异不显著。此外,弱光胁迫显著降低圆叶决明的Car含量。3弱光胁迫下,圆叶决明下位叶的受伤害程度大于上位叶,表现为叶肉细胞变形,细胞膜破裂,单位细胞内的叶绿体数目减少,个体变小。随弱光胁迫程度的加重,叶绿体基粒片层膨胀解体,基质片层断裂,淀粉粒明显减少,甚至出现空洞。4弱光胁迫导致圆叶决明叶片的净光合速率极显著下降、气孔导度降低,而胞间CO2浓度极显著升高,气孔限制值(Ls=1-Ci/Co)降低。弱光胁迫下,圆叶决明暗呼吸速率、光补偿点、光饱和点、表观量子产量、羧化效率降低,CO2饱和点降低,而CO2补偿点变化不大。说明弱光胁迫对圆叶决明光合作用的影响既有气孔因素也有非气孔因素。5弱光胁迫导致圆叶决明叶片光合机构受损,PSⅡ有活性的反应中心数量减少,关闭程度增加,最小荧光产量上升,最大荧光产量下降,可变荧光下降,最大光化学效率下降。弱光胁迫后,QA被迅速还原,引起QA-的大量积累,同时,电子传递体减少,电子从QA-向QB的传递受阻,电子传递的量子效率降低。此外,弱光胁迫导致圆叶决明单位面积叶片的PSⅡ反应中心捕获的激发能用于能量耗散的比例上升,用于电子传递的能量减少,PSⅡ反应中心性能指数极显著降低。6弱光胁迫下,圆叶决明叶片的硝酸还原酶活性下降,NO3-_N含量增加,二者呈极显著的负相关关系。同时,弱光胁迫还导致圆叶决明叶片可溶性蛋白含量下降。7弱光胁迫导致圆叶决明叶片SOD、POD活性提高,CAT活性极显著下降,O2.-产生速率提高,H2O2、MDA含量以及膜透性增加,引起膜脂过氧化,膜系统受损。更多还原

【Abstract】 Chamaecrista rotundifolia interplanted in orchards can prevent soil erosion, improve soil fertility and the ecological environment, enhance and improve fruit trees growth and fruit quality. Low light stress caused by the shading of fruit trees inhibited Chamaecrista rotundifolia’s growth seriously. Up to date, report about the mechanism of low light stress on Chamaecrista rotundifolia’s growth is not found. In order to illustrate the physiological mechanisms of low light stress on Chamaecrista rotundifolia’s growth, photosynthesis, chlorophyll fluorescence parameters, nitrogen metabolism, reactive oxygen metabolism were studied.The main conclusions are as follows:1 50%LI(50% light intensity),30%LI(30% light intensity) and 10%LI(10% light intensity) treatments decreased Chamaecrista rotundifolia’s height,stem diameter,leaf number and leaf area comparing with CK(natural light) treatment, indicating that low light stress could inhibit the growth of Chamaecrista rotundifolia, and the inhibition increased with the deeper degree of low light stress.2 Under low light stress, not only the contents of Chla, Chlb and the rate of Chla/Chlb were reduced, but also the content of Carotenoid(Car) was reduced. Comparing with upper leaves, the effect of low light stress on photosynthetic pigment content was more serious.3 Low light stress had markedly effects on chloroplast ultrastructure of Chamaecrista rotundifolia. Mesophyll cell deformated, cell membrane ruptured, the number of chloroplast in unit cells decreased and the individuals became smaller under low light stress. With the low light stress increased, grana lamellae expansed and disintegrated, stromal lamellae fractured, the number of starch grains in chloroplast decreased.4 Net photosynthetic rate, stomatal conductance and stomatal limitation value decreased significantly under low light stress while intercellular CO2 concentration increased significantly. Low light stress also decreased dark respiration rate, light compensation point, light saturation point, the apparent quantum yield, the carboxylation efficiency, CO2 saturation point, and little change in CO2 compensation point was found under low light stress. The results showed that both stomatal and non-stomatal factors affected the photosynthesis of Chamaecrista rotundifolia.5 The photosynthetic apparatus of Chamaecrista rotundifolia leaves were damaged under low light stress, and the number of PSⅡactive reaction center decreased with the closure level increased. Under low light stress, the minimal fluorescence production increased, while the maximal fluorescence production, variable fluorescence, maximal photochemical efficiency decreased. QA restored remarkably causing the mass accumulation of QA-. At the same time, the electronic transmission reduced, leading to the inhibition of electron transfer from QA- to QB, and the decrease of electron transfer rate. In addition, energy dissipation increased while energy in electron transfer and performance index of PSⅡdecreased significantly.6 Low light stress reduced nitrate reductase activity and enhanced NO3-_N content in Chamaecrista rotundifolia leaves. Nitrate reductase activity and NO3-_N content had highly significant negative correlation. Under low light stress, the content of soluted protein delined.7 SOD and POD activities of Chamaecrista rotundifolia leaves increased while CAT activity decreased significantly under low light stress which resulted in the increase of O2.- producing rate, H2O2 and MDA content, and membrane permeability, eventually caused membrane lipid peroxidation and membrane system damage.更多还原