Photosynthetic characteristics and comprehensive evaluation of introduced hybrid poplar

The photosynthetic parameters（ net Photosynthetic rate，transpiration rate and water use efficiency） of 22 introduced hybrid poplars were measured by using LI-6400XT portable photosynthetic apparatus. The diurnal dynamics of the photosynthetic parameters of the introduced hybrids poplar were analyzed and their photosynthetic capacity were comprehensively evaluated. The hybrids poplar with strong photosynthetic capacity were selected to provide a scientific reference for the breeding. The results showed that the diurnal variation of Pn and Tr of introduced hybrid poplar presented a single peak or bimodal curve，while some clones had obvious“ midday depression of photosynthesis” phenomenon and the peak time varied slightly among clones of different Pn and Tr. WUE of all clones reached the maximum at 8：00 with a sharp rise from 18:00 to 20：00. Additionally，there were slight differences among the times when the low value of WUE of each clone occurs. Though the photosynthetic parameters of each clones were significantly different（ p<0.01），there were correlations among the photosynthetic parameters of varying degrees. Comprehensive evaluation showed that the ones had stronger photosynthetic ability with higher comprehensive index score of LD-3，84-306，LX-2 and 108. Thus，they could be promoted in Ili region with rich light and heat resources.