不同臭氧胁迫水平下4种绿化树种基于叶面尺度的光合荧光特性

Photosynthetic fluorescence characteristics of four greening tree species based on leaf scale under different ozone stress levels.

地表臭氧(O_(3))是目前公认的具有植物强氧化毒性的光化学二次污染物,对植物光合系统造成严重损坏,阻碍森林生态系统碳汇等服务功能发挥。本研究采用开顶式气室装置和基于叶片尺度的叶绿素荧光成像技术,研究北京4种常见城市绿化树种(白蜡Fraxinus chinensis、二球悬铃木Platanus orientalis、刺槐Robinia pseudoacacia和国槐Sophora japonica)的光合叶绿素荧光特征在5个O_(3)浓度下的剂量特征。结果表明,随着O_(3)浓度的升高,PSII反应中心最大光量子产率(QY_(max))、稳态光适应非光化学荧光淬灭系数(NPQ_(Lss))、稳态荧光衰减参数(Rfd_(Lss))、PSII反应中心实际光化学量子效率(PhiPS2_(Lss))和PSII反应中心光稳态最大光量子效率(F_(v)'/F_(m)')均显著降低,稳态光适应光化学淬灭系数(qP_(Lss))变化不显著。除了NPQ_(Lss),不同绿化树种各项叶绿素荧光指标之间均存在显著性差异。4种树种的各项荧光指标与O_(3)剂量(AOT40,小时O_(3)浓度大于40 nmol·mol^(-1)的累计值)间具有显著的线性相关关系。整张叶片的叶绿素荧光成像反映出随着O_(3)浓度升高PSII反应中心逐渐受到损害的过程,光合能力降低遵循“叶缘先于叶肉,叶肉先于叶脉”的规律。叶绿素荧光成像技术可以在叶面尺度上反映植物对O_(3)胁迫的时空响应特征,具有一定的应用前景。

Ground-level ozone(O_(3))is considered as a secondary air pollutant with strong oxidative toxicity to plants,which causes serious damage to plant photosynthetic system and impedes forest carbon sequestration.In this study,based on leaf-scale chlorophyll fluorescence imaging technology,the open-top chambers were used to measure photosynthesis fluorescent parameters and investigate ozone dose-response relationships of four urban greening tree species(Fraxinus chinensis,Platanus orientalis,Robinia pseudoacacia,and Sophora japonica)in Beijing.The results showed that with the increases of O_(3)concentration,the maximum photon yield of PSⅡreaction center(QY_(max)),the steady-state light adaptive non-photochemical fluorescence quenching coefficient(NPQ_(Lss)),the steady-state fluorescence attenuation parameter(Rfd_(Lss)),the actual photochemical quantum efficiency of PSⅡreaction center(PhiPS2_(Lss))and the photostable maximum photon efficiency of PSⅡreaction center(F_(v)'/F_(m)')decreased significantly,while the steady-state light adaptive photochemical fluorescence quenching coefficient(qP_(Lss))did not change.Except for Rfd_(Lss),there were significant differences in chlorophyll fluorescence parameters among different greening tree species.All the four species showed a significant negative correlation between fluorescence parameters and the O_(3)dose index AOT40(cumulative value of hourly ozone concentration exceeding 40 nmol·mol^(-1)).The chlorophyll fluorescence imaging of the whole leaf reflected the process that the PSII reaction center was gradually damaged with the increases of O_(3)dose,and the reduction of photosynthetic capacity followed the order from leaf margin to leaf mesophyll to leaf vein.Chlorophyll fluorescence imaging technology could reflect the spatio-temporal response characteristics of plants to O_(3)stress on leaf scale,with certain application prospect.