Analysis on photosynthesis physiological characteristics of Alnus cremastogyne at different stand ages

The photosynthetic physiological characteristics of Alnus cremastogyne seedlings with two different stand ages(3-year-old,8-year-old) were systematically determined and analyzed by using Li-6400 portable photosynthesis measuring system.The results are as follows:(1)The diurnal variation values of net photosynthetic rate(Pn) of the leaves at different parts of A.cremastogyne with two different stand ages had not only commonness but also uncommon characteristics.The commonness is that both the upper and lower parts of the two alder's Pn tended to a same particular value at 8 am.,14:00,18:00;the uncommon characteristics is that the 3-year-old alder's upper and lower parts diurnal average variation curves both were single peak,the peak values occurred at 12:00,while that of 8-year-old alder had double peaks,the peak values both appeared at 10:00 and 16:00.(2)The order of the Pn of the two alder plants in four directions from big to small is: June'sApril'sSeptember'sOctober's.To the 8-year-old alder,the orientation affected greatly on each quarter's Pn,and to the annual average Pn,the four directions of 8-year-old alder were bigger than that of 3-year-old alder,it is to say that the photosynthetic capacity of the middle-aged stand was much more better than the young one.(3)For the upper part leaves and lower part leaves of the two different age A.cremastogyne,there were significant differences(p≤ 0.017) in the internal processing among the three factors(upper leaves,lower leaves,different months).There was a significant interaction between the two factors(stand age and the month),while the other two interaction did not reach a significant difference of 5 percent level.