Study On The Photosynthetic And Physiological Characteristics Of Populus Rrsskii And P.alba×P.bolleana

The light-response curve,CO2-response curve,diurnal changes,annual variation and the recovery of rescission water stress of Populus russkii and P.alba×P.bolleana was investigated which using Li-COR 6400 portable photosynthesis system.The results show that:The diurnal changes of Populus russkii and P.alba×P.bolleana ware basically identical,the Pmax,Q,Rday and k of the P.alba×P.bolleana was a little higher,but the LCP and LSP of the Populus russkii higher than the P.alba×P.bolleana.In sunny day the diurnal variation of Pn,Gond and Tr of Populus russkii exhibited double-peak pattern,and the peaks occurred at 11:00 and 16:00 respeetively.There was a significant midday depression with A.sinensis, which was caused principally by stomatal factors such as stomatal conductance.The peaks of the annual variation occurred 6th July and 24th August, stomatal limitation was the main reason of diurnal variation and annual variation which had formed the low ebb.The weight method was used in the research which was under the dry stress and dry stress relieved by la the young plants of Populus russkii and P.alba×P.bolleana.We setted the gradient of the soil moisture as follows:6%,8%,10%,12%,13%,14%,16%,18%,20%.The results indicated that the photosynthetic physiology of Populus russkii and P.alba×P.bolleana reduced as the gradient depressed.The reason of the Pn reduced was brought by Gs,P.alba×P.bolleana reduces more obviously. When the soil moisture contents were less than 8%,physical index of Populus russkii and PalbaX P.bolleana were damaged,and unable restored after the rehydration.When soil moisture contents were over 10%,it would be recovered after the rehydration,although photosynthetic capacity reduced in the process of dry stress,but after rehydration it resumed,and 18%was the best soil moisture content for Populus russkii and P.alba×P.bolleana.