补增UV-B辐射对焕镛木(Woonyoungia septentrionalis)叶片光合参数的影响

补增UV B辐射 ,焕镛木 (Woonyoungiaseptentrionalis)叶片的光饱和光合速率较自然光下的降低 2 9% ,叶片的光合量子产率降低 5 0 .4 % ,光能转换效率亦降低 4 9% .补增UV B辐射抑制光下呼吸速率 (Rd) ,但不明显改变不包括光下呼吸的CO2 补偿点 .补增UV B辐射 ,焕镛木叶片的RuBP饱和的最大羧化速率和最大电子传递速率分别较自然光下的低 4 3.4 %和 4 6 .4 % ,Jmax:Vcmax亦降低 ,显示补增UV B辐射对Jmax的影响较Vcmax明显 .补增UV B辐射亦引起磷酸三碳糖利用速率降低 .叶片多个生化过程被抑制可能是引起植物光合速率降低的原因 .补增UV B辐射 ,降低了气孔对空气CO2 浓度和相对湿度变化的敏感度 ,则可能影响植株对环境因素变化的适应性 .图 3表 4参 2 3

EFFECT OF SUPPLEMENTARY UV-B RADIATION ON PHOTOSYNTHETIC PARAMETERS IN LEAVES OF WOONYOUNGIA SEPTENTRIONALIS

The supplementary UV B radiation decreased light saturated photosynthetic rate in leave of W. Septentionalis by 29% in comparison with the grown in ambient condition, and photosynthetic quantum yield apparently declined by 50.4% and the efficiency of light energy conversion also decreased by 49%. The respiration rate in the light ( R d) was inhibited by the supplementary UV B radiation, but the CO 2 compensation point in the absence of R d was not changed significantly. The Maximum RuBP saturated rate of carboxylation and the maximum rate of electron transport decreased by 43.4% and 46.4%, respectively, as well as the ratio of J max : V cmax decreased. It might suggest that the effect of UV B radiation on J max would be more significant than that on V cmax . The UV B radiation also caused the decrease of the rate of triosphosphate utilization. The results suggested that the biochemical multi processes in photosynthesis would be inhibited by UV B radiation and photosynthesis rate decrease significantly. UV B radiation caused the decrease of stomatal sensitivity to the changing atmospheric CO 2 concentration and the relative humidity, which would affect the adaptation to the changing environmental factors by the plants of Magnoliaceae under enhanced UV B radiation. Fig 3, Tab 4, Ref 23