准噶尔荒漠3种短命植物气体交换特征的日变化

采用LI-6400便携式光合测定仪,在晴天条件下对准噶尔荒漠3种典型短命植物东方旱麦草(Eremopyrum orientale)、卷果涩芥(Malcolmia scorpioides)和四齿芥(Tetracme quadricormis)的气体交换特征的日变化规律进行了研究.结果表明:①东方旱麦草和卷果涩芥的净光合速率(简称Pn,后同)的日变化呈"双峰"型,14:00(采用时间均为北京时间,后同)左右存在明显的光合"午休"现象,四齿芥Pn的日变化呈"单峰"型,峰值出现在12:00与前两者的第一峰值出现时刻相同.3种植物蒸腾速率(简称E,后同)的日变化均呈"单峰"型,但不同植物的峰谷值出现时刻不同.水分利用效率(WUE)日变化,四齿芥呈"单峰"型,东方旱麦草和卷果涩芥呈"双峰"型,峰值分别出现在8:00～10:00之间,后两者第二峰值分别出现在16:00和18:00.②根据Pn、胞间CO2浓度(Ci)和气孔限制值(Ls)的变化方向,推测3种短命植物的光合"午休",东方旱麦草和卷果涩芥主要受非气孔因素限制,而四齿芥主要受气孔因素限制.③卷果涩芥和四齿芥两种十字花科草本日平均Pn、E 和WUE 均高于禾本科东方旱麦草,尤其卷果涩芥是一种高光合、高蒸腾、高水分利用率的物种.④相关分析结果表明,对Pn影响最显著的环境因子是光合有效辐射(PAR),对E影响最显著的因子3种植物各不相同.

Daily dynamics of gas exchange characteristics of three ephemeral plants in Dzungaria Desert

As pioneer plants, desert spring ephemerals play an important role in community succession, biodiversity maintenance and dune stabilization in desert ecosystems. We studied the diurnal changes in gas exchange of three desert spring ephemerals (Eremopyrum orientale, Malcolmia scorpioides, and Tetracme quadricormis, hereafter the genus names only) under natural conditions in the desert area of the Dzungaria Basin. Net photosynthetic rate (Pn) of the three ephemerals all reached the highest values at 12:00. Regarding the curves of diurnal variation, Pn of Eremopyrum and Malcolmia had two peaks, and an obvious midday depression occurred at 14:00; Transpiration rate (E) of all the three ephemerals had only one peak; water use efficiency (WUE) of Eremopyrum and Malcolmia had two peaks, and that of Tetracme had only one. One peak of WUE of all the three ephemerals occurred between 8:00 and 10:00, and the second peak of WUE of Eremopyrum and Malcolmia occurred between 16:00 and 18:00. Based on the tendency of changes in Pn, intercellular CO2 concentration (Ci) and stomatal limitation (Ls), we speculate that the midday depressions of Eremopyrum and Malcolmia were not controlled by stomatal factors, while those of Tetracme were. Daily mean values of Pn, E and WUE of Malcolmia and Tetracme were higher than those of Eremopyrum. The correlation analyses showed that the factors affecting Pn could be ranked as PAR > Gs > Ta > VPD > RH, and that the factors affecting E were different among the three ephemerals.