西南地区9种乡土杨树的秋季光合特性比较

季节是影响植物光合特性的重要因素之一，而树木秋季光合作用为次年生长储备营养物质，也是林木育种的重要指标。为了解西南地区9种乡土杨树在秋季生长期对光能的利用效率，以收集于西南地区不同海拔的滇杨、大叶杨、藏川杨、德钦杨、昌都杨、康定杨、乡城杨、西南杨和三脉青杨为研究对象，在10月初采用LI-6400便携式光合测定仪对其光合参数进行测定。结果表明:1）滇杨和藏川杨的生长量优于其他树种。2）乡城杨净光合速率（P_n）日变化呈现为不对称的双峰曲线，其他8种杨树均为单峰曲线，但峰值出现的时间不同；而9种杨树的蒸腾速率（T_r）日变化均为单峰曲线，大叶杨Tr峰值出现在12:00，其他8种杨树均在14:00；9种杨树的气孔导度（G_s）、胞间CO₂浓度（C_i）和水分利用率（WUE）日均值均存在极显著差异，昌都杨G_s日均值最大（0.37 mmol·m^-2·s^-1），康定杨C_i日均值最小（284.222 4 μmol·mol^-1），且水分利用率（WUE）最高（4.996 6 μmol·mmol^-1）。3）综合4个光合参数，西南杨和康定杨具有较大的后续生长潜力，且康定杨耐旱性较强，而昌都杨和大叶杨耐旱能力较弱。因此，在今后推广应用及经营管理中，需要考虑不同树种对水分需求的差异。

Comparison of Photosynthetic Characteristics of Nine Poplar Species in Southwest China in Autumn

Season is one of important factors affecting the photosynthetic characteristics of the plants,and photosynthesis of trees in autumn reserves nutrients for the next year’s growth as well as an important index of tree breeding.In order to understand the light utilization efficiency of poplar species in southwest China during autumn,nine poplar species,which distribute at different altitudes in southwest China,including Populus yunnanensis,P.lasiocarpa,P.szechuanica var.tibetica,P.haoana,P.qamdoensis,P.kangdingensis,P.xiangchengensis,P.schneideri and P.trinervis,were used as the research materials,and the photosynthetic parameters were measured by LI-6400 portable photosynthesis measurement system in early October.The results showed that 1) the growth of P.yunnanensis and P.szechuanica var.tibetica was superior to other poplar species.2) The curve of net photosynthetic rate (P_n) of P.xiangchengensis was bimodal while those of other poplar species unimodal,but the peak value of P_n appeared at different time.The diurnal variation of transpiration rates (T_r) of nine poplar species were unimoal curves,and the maximum value of T_r in P.lasiocarpa occurred at 12:00,while other eight poplar species occurred at 14:00.The mean values of stomatal conductance (G_s),intercellular CO₂ concentration (C_i) and water use efficiency (WUE) were all extremely and significantly different,and P.qamdoensis had the maximum mean value of G_s (0.37 mmol·m^-2·s^-1),P.kangdingensis had the minimum mean value of C_i (284.222 4 μmol·mol^-1) and the maximum mean value of WUE (4.996 6 μmol·mmol^-1).3) Comprehensive analysis of the photosynthetic parameters indicated that P.schneideri and P.kangdingensis should have great potential for subsequent growth.Meanwhile,P.kangdingensis has showed strong drought tolerance,but the drought tolerances of P.qamdoensis and P.lasiocarpa were weak.Therefore,attention should be paid to the differences in water demand among different poplar species during spreading application and management.