Photosynthetic characteristics of hybrid clones of Populus deltoides and P. ussuriensis.

Photosynthetic characteristic is an important indication of genetic improvement of poplar.In order to study the photosynthetic characteristics of hybrid clones of Populus deltoides 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.