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自然条件下(5~10月份),利用Li-6400便携式光合作用测定系统对北京大兴地区集约栽培欧美107杨(Populus×euramericanacv.“74/76”)生理生态特性进行研究,探讨叶片在水分胁迫状态下光合作用、呼吸作用和蒸腾作用动态规律,并揭示其主要影响机理。实验结果表明叶片净光合速率(Pn)日变化均为单峰曲线,且Pn日平均值从春季到秋季呈下降趋势。从整个生长季来看,光合有效辐射PAR(r=0·815)和气孔导度Gs(r=0·805)与Pn的相关性显著,通过每月相关性分析,5、8月份影响Pn的主导因子为PAR和Gs,6、7月份影响Pn的主导因子为Gs,9、10月份影响Pn的主要因素为PAR。根据Fsrquhar和Sharkey提出的气孔限制和非气孔限制判断方法对Pn日变化进行分析,5月份8:00Pn达到峰值后由于气孔导度降低引起Pn下降,16:00以后由于非气孔因素PAR的降低,使得Pn继续降低;6、7月份8:00以后Pn降低限制因素同5月份一样由气孔导度降低引起,但是14:00左右,由于植物体内水分严重亏缺,叶片气孔不能正常开启使得叶片Pn、R和Tr均不能正常进行,8~10月份Pn降低主要受PAR限制。叶片呼吸速率(R)的主要影响因子为温度,且R的日变化和季节变化与大气温度(Ta)变化趋势基本一致,一天中清晨、傍晚Ta和R均为低点,14:00左右Ta和R都达到最大值,同样在季节变化中R和Ta在6、7月份最高,10月份最低。蒸腾速率(Tr)日变化全为单峰曲线,其最大值出现在12:00~14:00左右,Tr变化与许多环境因子和生理因子都具有密切的相关性,就整个生长季来说,PAR是其最主要的影响因子,然而叶片气孔限制值(LS)、Gs、叶片大气水汽压差(VpdL)、Ta等生理生态因素在不同月份分别起着极其重要的作用。
Under natural conditions (from May to October), the physiological and ecological characteristics of intensive cultivation Populus × euramericanacv. “74/76” in Daxing, Beijing were studied by Li-6400 portable photosynthesis system. The effects of water stress State of photosynthesis, respiration and transpiration of the dynamic law and reveal the main impact mechanism. The experimental results showed that the diurnal changes of net photosynthetic rate (Pn) of leaves were unimodal curve, and the daily average of Pn decreased from spring to autumn. Through the whole growing season, the correlation between PAR (r = 0.885) and stomatal conductance Gs (r = 0.805) and Pn was significant. According to the monthly correlation analysis, the influence of Pn The dominant factor is PAR and Gs, the dominant factor affecting Pn in June and July is Gs, and the main factor affecting Pn in September and October is PAR. According to the stomatal limitation and non-stomatal limitation judgment method proposed by Fsrquhar and Sharkey, the daily variation of Pn was analyzed. Pn decreased due to the decrease of stomatal conductance after peaked at 8: 00 in May. After 16:00, due to the decrease of non-stomatal PAR, Making Pn continue to decrease; June and July after 8:00 Pn reduce the same limiting factors as in May by stomatal conductance decreased, but around 14:00, due to a serious shortage of water in plants, leaf stomatal opening can not be normal leaves Pn , R and Tr can not be normal, 8 to 10 Pn reduction mainly due to PAR constraints. The main influencing factors of leaf respiration rate (R) were temperature, and the diurnal and seasonal variations of R were basically consistent with the changes of atmospheric temperature (Ta). One day in the morning and the evening, Ta and R were low and about 14:00 Ta And R both reached their maximum values. Also in the seasonal changes, R and Ta were the highest in June and July and the lowest in October. The diurnal variations of transpiration rate (Tr) were all single peak curves, with the maximum value occurring around 12: 00-14: 00. The changes of Tr were closely related to many environmental and physiological factors. For the whole growing season, PAR was the most important factor. However, the leaf stomatal limitation value (LS), Gs, leaf vapor pressure difference (VpdL), Ta and other physiological and ecological factors play an extremely important role in different months.