临泽绿洲边缘区棉花群体光合速率、蒸腾速率及水分利用效率

Photosynthetic rate,transpiration rate,and water use efficiency of cotton canopy in oasis edge of Linze

在甘肃河西走廊中部黑河中游绿洲边缘区,于6月下旬和8月上旬,利用Li-8100土壤碳通量测定系统与改进的同化箱联合对田间条件下早熟陆地棉(Gossypium hirsutum)品种新陆早8号的群体光合特性进行了研究.结果表明:试验地6月下旬的土壤呼吸速率和土壤蒸发速率显著高于8月上旬(P<0.01);棉花群体光合速率日变化均呈"单峰型",6月下旬的群体光合速率显著高于8月上旬,其日平均值分别为(43.11±1.26)和(24.53±0.60)μmolCO2.m-2.s-1,差异极显著(P<0.01);群体蒸腾速率日变化也呈"单峰型",6月下旬和8月上旬的日平均值分别为(3.10±0.34)和(1.60±0.26)mmolH2O.m-2.s-1,两者存在极显著差异(P<0.01);6月下旬和8月上旬的群体水分利用效率日平均值分别为(15.67±1.77)和(23.08±5.54)mmolCO2.mol-1H2O,但差异不显著(P>0.05).两生育时期棉花群体光合速率与温度、光合有效辐射及土壤含水量均呈正相关关系.表明棉花群体光合速率在6月下旬和8月上旬均没有出现中午光合下调,8月由于土壤水分降低和植物叶片衰老,棉花群体光合速率和蒸腾速率显著降低,但水分利用效率并无显著下降.

The measurement system of Li-8100 carbon flux and the modified assimilation chamber were used to study the photosynthetic characteristics of cotton （Gossypium hirsutum L.） canopy in the oasis edge region in middle reach of Heihe River Basin,mid Hexi Corridor of Gansu. At the experimental site,soil respiration and evaporation rates were significantly higher in late June than in early August,and the diurnal variation of canopy photosynthetic rate showed single-peak type. The photosynthetic rate was significantly higher （P0.01） in late June than in early August,with the daily average value being （43.11±1.26） μmol CO2·m-2·s-1 and （24.53±0.60） μmol CO2·m-2·s-1,respectively. The diurnal variation of canopy transpiration rate also presented single-peak type,with the daily average value in late June and early August being （3.10±0.34） mmol H2O·m-2·s-1 and （1.60±0.26） mmol H2O·m-2·s-1,respectively,and differed significantly（P0.01）. The daily average value of canopy water use efficiency in late June and early August was （15.67±1.77） mmol CO2·mol-1 H2O and （23.08±5.54） mmol CO2·mol-1 H2O,respectively,but the difference was not significant （P0.05）. Both in late June and in early August,the canopy photosynthetic rate was positively correlated with air temperature,PAR,and soil moisture content,suggesting that there was no midday depression of photosynthesis in the two periods. In August,the canopy photosynthetic rate and transpiration rate decreased significantly,because of the lower soil moisture content and leaf senescence,but the canopy water use efficiency had no significant decrease.