【作者】 梁婵娟；

【导师】 周青；

【作者基本信息】 江南大学 ， 环境工程， 2006， 博士

【摘要】 臭氧层衰减诱发UV-B辐射抵达地球表面增加,对陆生植物的影响引起学术界广泛关注。探讨稀土对UV-B辐射胁迫伤害植物的影响与机理,是稀土环境植物学研究的拓展和延伸,其结果可为减轻UV-B辐射伤害植物的防护对策提供参考。本文采用水培方法,以油料作物大豆(Glycine max)、品种“垦农18”为试验材料,研究稀土铈对UV-B辐射胁迫下植物光合作用光反应的影响。探讨了Ce(Ⅲ)对UV-B辐射胁迫下植物光合作用原初反应、电子传递、光合放氧及光合磷酸化的影响机制,并利用电镜技术同步观察大豆叶片叶绿体超微结构在上述条件下的相应变化。主要内容如下:i.确定了Ce(Ⅲ)对大豆幼苗的“剂量-效应”和“时间-效应”通过叶面喷施不同剂量Ce(Ⅲ),考察大豆幼苗光合速率(Pn)动态变化,发现各个剂量处理下Pn连续15d动态变化规律不尽相同,证实Ce(Ⅲ)对大豆幼苗光合作用的影响具有剂量效应和时间效应。20mg·L-1Ce(Ⅲ)处理下Pn的增幅最大,且增幅维持较高水平的时间最长,由此确定,该剂量为本实验中的适宜剂量(下同)。ii.确定了大豆苗期UV-B辐射的适宜剂量和时间测定不同UV-B辐射剂量下大豆叶片Pn变化,发现UV-B辐射剂量与叶片Pn呈显著负相关。与对照植株相比,UV-B辐射强度为0.15W·m-2时,Pn显著降低;为0.45W·m-2时,Pn的降幅>50%。因此确定,0.15 W·m-2和0.45 W·m-2UV-B辐射为本实验中的低(T1)、高(T2)效应剂量。iii.发现Ce(Ⅲ)可缓解UV-B辐射对大豆光合作用伤害Ce(Ⅲ)能提高大豆幼苗叶绿素(Chl)与类胡萝卜素(Car)含量、气孔导度(Gs)、饱和光光合速率(Ps)、饱和CO2光合速率(Pm)、表观量子效率(AQY)与羧化效率(CE),在一定程度上减缓了因UV-B辐射降解叶绿素、增加气孔阻力、降低量子产额、光合磷酸化和二磷酸核酮糖羧化酶(RuBP羧化酶)活性而导致的Pn下降。Car含量增加能有效防止UV-B辐射引起Chl发生光氧化,减轻了UV-B辐射对光系统的损伤。动态测定结果显示,由于Ce(Ⅲ)介导,减缓了5项指标在UV-B辐射期(1~5d)的下降趋势,而加快了在UV-B辐射结束后(6~11d)的上升速度,缩短了恢复历程,最终呈现较好的恢复效果,且低剂量的恢复效果好于高剂量。Pn与Chl含量、Gs、AQY及CE相关性分析结果表明,不同剂量UV-B辐射对植物光合作用的影响机制存在差异。如低剂量下Pn变化更多受Chl含量和AQY影响,高剂量下Pn消长主要与CE与Gs相关。另外,不同UV-B辐射剂量下,Ce(Ⅲ)缓解Pn递减的机制不尽一致。低剂量辐射下,Ce(Ⅲ)对AQY的调控对Pn影响最大,而在高剂量下,Ce(Ⅲ)维持较高Gs与CE活性最为关键。更多还原

【Abstract】 Gradual depletion of stratospheric ozone layer in atmosphere has lead to increase in solar UV-B radiation that reaches earth surface. Many investigations concerning the influence of UV-B radiation on different terrestrial plants were carried out during the last 25 years. Study on the effect of rare earths elements on plants exposed UV-B radiation aimed to develop and extend the research for environmental botany of rare earths. The results of this study could provide a new direction for the ecological protection of plants against the damage of UV-B radiation. In this paper, effects of cerium(Ⅲ) on photosynthetic light reactions in soybean seedlings exposed to supplementary ultraviolet-B radiation(UV-B) were studied by hydroponics under laboratory conditions. Various techniques such as photosynthetic gas exchange, chlorophyll fluorescence as well as scanning electron microscope were used to investigate the regulating mechanism of Ce(Ⅲ) on photosynthetic primary reaction, electron transport, photosynthetic oxygen evolution and photophosphorylation and changes of chloroplast ultrastructure in leaves exposed UV-B radiation. The main results were below:i. Dose-effect and time-effect relation between the dose of Ce(Ⅲ) and photosynthetic rate in leaves of soybeanDynamic changes of photosynthetic rate(Pn) in leaves sprayed with Ce(Ⅲ) solution at various concentration showed that the trends with different treatments was not the same during 15 day, and proved that the effect of Ce(Ⅲ) on Pn were closely related to its concentration and treating time. The increase range of Pn in leaves treated with 20mg·L-1 Ce(Ⅲ) was largest and the period with higher lever was longest, which proved that this concentration was suitable in our experiments.ii. Dose-effect relation between the intensity of UV-B radiation and photosynthetic rate in leaves of soybeanChanges of Pn in leaves exposed different intensity of UV-B radiation showed that Pn was significantly and negatively correlated with intensity of UV-B radiation. Compared with the control sample, Pn was significantly decreased in leaves exposed to UV-B radiation at the level of 0.15W·m-2 while Pn was decrease more than 50% in leaves exposed to UV-B radiation at the level of 0.45W·m-2. In our experiment, the lower intensity of UV-B radiation was 0.15W·m-2 and the higher one was 0.45W·m-2.iii. The protective effect of Ce(Ⅲ) on photosynthesis in leaves of soybean against the damage of UV-B radiation更多还原