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以4年生曼地亚红豆杉扦插苗为试材,用一层遮荫和两层遮荫处理3个月,研究不同程度遮荫对曼地亚红豆杉光合作用的影响。实验前1个月将苗木移栽至花盆中置于大棚内进行正常水分管理。将苗木分为3组,每组10株,3个重复,分别进行遮荫处理。处理3个月后测定叶片净光合速率(Pn),气孔导度(Gs),蒸腾速率(E),胞间CO2浓度(Ci),初始荧光(F0)、最大荧光(Fm)和可变荧光(FV)光系统II的最大量子产量(Fv/Fm)。结果表明遮荫处理下曼地亚红豆杉Pn、E、CE与对照相比显著下降,水分利用效率(WUE)一层遮荫处理最高。叶绿素a/b升高,总叶绿素含量下降。Gs,Fv/Fm在胁迫期间没有显著变化。推测曼地亚红豆杉在遮荫处理下光系统II(PSII)光能转化能力保持相对稳定,对水分有较高的利用效率,引起光合下降的主要是非气孔因素,即羧化效率的显著下降。
A 4-year-old man-made yew cuttage of Taxus chinensis was used as test material, with one layer of shading and two layers of shading treatment for 3 months to study the effects of different degrees of shading on the photosynthesis of Taxus mairei. One month before the experiment, the seedlings are transplanted to pots and placed in a greenhouse for normal water management. The seedlings were divided into 3 groups, 10 plants in each group, 3 replicates were shaded separately. The leaf photosynthetic rate (Pn), stomatal conductance (Gs), transpiration rate (E), intercellular CO2 concentration (Ci), initial fluorescence (F0), maximum fluorescence (Fm) and variable fluorescence (FV) Maximum quantum yield of photosystem II (Fv / Fm). The results showed that the Pn, E and CE of Taxus mairei under shading treatment significantly decreased compared with the control, and the highest water use efficiency (WUE) in the layer of shading was obtained. Chlorophyll a / b increased, the total chlorophyll content decreased. Gs, Fv / Fm did not change significantly during stress. It is speculated that the light energy conversion ability of PSII was relatively stable under shading treatment, and had higher utilization efficiency to water, and the non-stomatal factor that led to photosynthesis decline was the significant decrease of carboxylation efficiency .