用氧电极仪、红外CO2气体分析仪及叶绿素荧光仪，结合透射电镜技术对几个杂种杨无性系在光胁迫下的光系统Ⅱ活性、光合色素及叶绿体超微结构进行了测定。随着预处理光强的增加，各无性系叶片的净光合速率和光系统Ⅱ放氧活性明显下降。二倍体无性系B11的光系统Ⅱ最大光化学效率(Fv/Fm)及实际光化学效率[(Fm′-F)/Fm′]高于两个三倍体无性系B346和B342。强光下三倍体无性系B346的非光化学淬灭远高于B342和二倍体无性系B11。叶绿素含量和光合速率没有明显的线性关系，叶绿素a/b含量在自然光胁迫下存在季节变化，受强光胁迫2个三倍体无性系的叶绿素a/b增大。预处理光强PFD超过3 000 μmol photons·m-2·s-1，各无性系的基粒类囊体片层结构遭到破坏，但二倍体无性系的类囊体片层结构受破坏程度较三倍体无性系轻。叶绿体蛋白合成抑制剂(硫酸链霉素，SM)可加剧叶绿体超微结构的破坏。
The photosynthetic rate, oxygen evolution activity of the PSⅡ center, and chloroplast ultrastructure of three hybrid poplar clones under light stress were investigated using an oxygen electrode, IRGA (infra-red CO2 gas analyzer), chlorophyll fluorometer and transmission electron microscopy. The photosynthetic rate and PSⅡ oxygen evolution varied negatively with the pretreatment-PFD (Photon Flux Density), whereas the chlorophyll a/b varied positively with the pretreatment-PFD for two triploid clones. Both the maximal and effective PSⅡ efficiencies of the diploid clone B11 were much higher than those of the two triploid clones B346 and B342. The non-photochemical quenching of triploid B346 was higher than in the B342 and B11 clones. The photosynthetic capacity and resistance to light stress for the diploid clone was higher than in triploid clones. There was no close relationship between chlorophyll content and photosynthetic rate, there was seasonal variation in CHL content and CHLa/b, and the ratio of CHLa to CHLb decreased with enhancing pretreatment-PFDs. The chloroplast protein inhibitor streptomycin (SM) blocked the re-synthesis process of D1 protein. Transmission electron micrographs showed that 1h strong irradiance exposure could result in the decomposition of the lamellar structure of grana. Clones B11 and B342 were more resistant to light stress than clone B346.