中文摘要：

对杨树光合特性的研究一直是杨树遗传改良的一个重要方面。为探讨美洲黑杨与大青杨杂种无性系苗期的光合特性和规律,以美洲黑杨与大青杨杂交所得3个生长及抗性等表现优良的杂种无性系1年生盆栽扦插苗为材料,采用Li-6400光合测定系统对3个无性系的光合作用指标进行测定。结果表明：在7月中旬,天气晴朗条件下,3个无性系的净光合速率和蒸腾速率日变化均呈不对称的双峰曲线,气孔导度和胞间CO2浓度日变化分别呈单峰和倒双峰变化趋势;编号为191的无性系净光合速率日变化曲线两次峰值均高于165和177,191和177的低值高于165;3个无性系的净光合速率-光响应曲线相近,净光合速率均随着光合有效辐射的增加而增大,接近光饱和点时上升趋势平缓;191的光饱和点高于165和177,而光补偿点低于165和177,表明191适应光强的能力强于165和177。

英文摘要：

Photosynthetic characteristic is an important indication of genetic improvement of poplar. In order to study the photosynthetic characteristics of hybrid clones of Populus deltoicles and P. ussuriensis, one-year-old potted cuttings of three hybrid clones （ # 191, # 177 and # 165）,which had better growth traits and resistance, were used as experimental materials for measurement of photosynthesis using Li-6400. The results from the measurement on a sunny day in the middle of July showed that there was a two-peak curve in the diurnal pattern of both the net photosynthetic rate and the transpiration rate of the three hybrids, while a one-peak curve and an inverse two-peak curve for stomata conductance and intercellular carbon dioxide concentration, respectively. Two peak values of daily changing curve of net photosynthetic rate of the sample of # 191 had higher values in net photosynthetic rates than # 165 and # 177, and the vale values of # 191 and # 177 were higher than that in # 165. The light response curves of net photosynthetic rate of three clones were similar to each other, and the net photosynthetic rate increased with the growth of photosynthetically active radiation, and then kept steady when reaching light satuation point. Light saturation point of # 191 was higher than that in # 165 and # 177. However, light compensate point of # 191 was lower than that of # 165 and # 177, suggesting that the ability of adapting radiation intensity of # 191 is better than that of # 165 and # 177.