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以LCA 4光合蒸腾测定系统进行大腺相思和多花相思叶片气体交换过程的测定 ,结果如下 :( 1 )净光合速率日变化明显 ,且变化趋势大体一致 ,即 1 0 :0 0～ 1 3:0 0具有较高的光合速率 ,其它测定时间相对较低。 ( 2 )两树种净光合速率存在差异 ,大腺相思高于多花相思 ,其最大值分别为 1 9.6 ( 1 0 :0 0 ) ,1 6 .1 ( 1 3:0 0 ) μmolm-2 s-1,日平均值分别为 1 1 .9,9.8μmolm-2s-1,反映了大腺相思的生长速度较多花相思快。 ( 3)大腺相思和多花相思蒸腾速率日变化明显 ,正午前后较高 ,1 3:0 0达到最大。日平均值多花相思略高于大腺相思 ,分别为 3.3,3.0mmolm-2 s-1,表明在相同的环境条件下大腺相思的耗水量低于多花相思。 ( 4)两树种蒸腾效率的日变化趋势大体上也类似 ,即在 9:0 0～ 1 1 :0 0较高 ,此期间大腺相思和多花相思的平均值分别为 5.51 ,4.2 1 μmolCO2 /mmolH2 O。日平均值大腺相思和多花相思分别为 3.84,2 .88μmolCO2 /mmolH2 O ,表明消耗等量的水分大腺相思比多花相思能固定更多的CO2 量 ,即有更高的水分利用效率
The results showed as follows: (1) The diurnal variation of net photosynthesis rate was obvious and the trend of change was generally the same, that is, 1 0: 0 0 ~ 1 3 : 0 0 has a higher photosynthetic rate, the other measurement time is relatively low. (2) There were differences in net photosynthetic rates between the two species. Acacia macroscopia was higher than Acacia, with the maximum values of 1 9.6 (1 0: 0 0), 1 6 .1 (1 3: 0 0) μmolm-2 s -1, the average daily values were 1 1 .9,9.8μmolm-2s-1, reflecting the growth of Acacia crassifolia agave faster. (3) The diurnal variations of transpiration rate of Acacia macrostachya and Acacia confusa were higher than before and after noon, reaching the maximum at 13:06. The average daily acacia flower slightly higher than the acacia, respectively, 3.3,3.0mmolm-2s-1, indicating that under the same environmental conditions Acacia water consumption is lower than Acacia. (4) The diurnal variation trend of transpiration efficiency of the two tree species is similar in general, that is, at 9: 0 0 ~ 1 1: 0 0, the average values of Acacia macrostachya and Acacia confusa are 5.51 and 4.2 1 μmolCO2 / mmolH2O. Daily average of Acacia macrostachya and Acacia acuminata were 3.84 and 2.88 μmolCO2 / mmolH2O, respectively, indicating that the same amount of water was consumed. Acacia acuminate could fix more CO2 than acacia, which means higher water use efficiency