摘要
银杏叶片遭受光量子通量密度（PFD）为1200μmolm-2s-1的强光胁迫后，净光合速率（Pn）、气孔导度（Gs）、细胞间隙CO2浓度（Ci）、PSⅡ光化学效率（Fv／Fm）和表现量子效率（AQY）都下降，而叶片在505nm处的光吸收（A505）、初始荧光水平（Fo）和荧光的非光化学猝灭（qN）上升。在去除强光胁迫数小时之后，这些参数都不能完全恢复。这就表明，虽然强光能引起严重的光抑制，可能涉及依赖叶黄素循环的热耗散和一部分PSⅡ反应中心的失活及破坏，但是导致光合速率降低的主要因素仍然是气孔导度的降低。
For understanding the photosynthetic characteristics of Ginkgo biloba L., we observed the response of photosynthesis to strong light in leaves 0f ginkgogrown under field conditions by using a portable photosynthetic measarement system (CI-301 ), a table ADC-225-MK3 CO2 gas analyzer and a portable fluorescence measurement system (PAM-2000).The saturating light intensity and the light compensation point for photosynthsis in ginkgo leaves were about 700 ~ 1 000 and 10 ~ 25 μmol photons m-2 s-1, respectively (Figs. 1, 2), both with higher values in summer than in autumn. In response t0 strong light (1200)μmol photons m-2 s- 1 ), the net photosynthetic rate (Pn), stomatal conductance (Gs), intercelluar CO2 concentration (Ci) (Figs. 3, 4), and the PS Ⅱphotochemical efficiency (Fv/Fm) (Fig.5) as well as the apparent quantum yield (AQY) of carbon assimilation (Fig. 6)decreased , while the initial fluorescence level (Fo), non-photochemicaal quenching (qN ) of chlorophyll fluorescence (Fig. 5 ), and the light absorbance at 505 nm (A505) (rig.7) increased. Furthermore, these parameters such as Pn,Gs, Ci, AQY, Fv/Fm and Fo could not recover t0 those levels before strong light treatment several hours after the removal of strong light stress.These results indicate that the main cause of the decline in Pn induced by strong ligh is the decrease in Gs, though severe photoinhibition occurs simultaneously. The severe photoinhibition is mainly due to partial inactivation and destruction of PS Ⅱ reaction centers than the xanthophyll - cycle - dependent thermal enery dissipation. The mechanism whereby strong light causes a decrease in Gs is worth furthr studying.
基金
国家自然科学基金!39570068
中国科学院重点基金
关键词
强光胁迫
净光合速率
银杏
光合作用
strong ligh stress, net photosynthetic rate, stomatal conductance , photoinhibition , the xanthophyllcycle, Ginkgo biloba
