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Oxygen isotope composition of CAM and C3Clusia species: non-steady-state dynamics control leaf water 18O enrichment in succulent leaves

机译:CAM和C3Clusia物种的氧同位素组成:非稳态动力学控制多汁叶片中叶水18O的富集

摘要

Leaf gas exchange and leaf water 18O enrichment (Δ18OL) were measured in three Clusia species under field conditions during dry and wet seasons and in Miconia argentea during the dry season in the Republic of Panama. During the dry season, all three Clusia species used crassulacean acid metabolism (CAM); during the wet season Clusia pratensis operated in the C3 mode, while Clusia uvitana and Clusia rosea used CAM. Large departures from isotopic steady state were observed in daytime Δ18OL of the Clusia species, especially during the dry season. In contrast, daytime Δ18OL was near isotopic steady state in the C3 tree M. argentea. Across the full data set, non-steady-state predictions explained 49% of variation in observed Δ18OL, whereas steady-state predictions explained only 14%. During the wet season, when Δ18OL could be compared with Clusia individuals operating in both C3 and CAM modes, steady-state and non-steady-state models gave contrasting predictions with respect to interspecific variation in daytime Δ18OL. The observed Δ18OL pattern matched that predicted for the non-steady state. The results provided a clear example of how non-steady-state control of leaf water 18O dynamics can shift the slope of the relationship between transpiration rate and daytime Δ18OL from negative to positive.
机译:在巴拿马共和国的旱季和雨季,在田间条件下测量了三种Clusia物种的叶片气体交换和叶片水18O富集(Δ18OL),在旱季期间,在Miconia argentea进行了测量。在干旱季节,所有三种克鲁萨属物种都使用了十字花科的果酸代谢(CAM);在雨季,Clusia pratensis以C3模式运行,而Clusia uvitana和Clusia rosea使用CAM。在白天克鲁斯氏菌物种的Δ18OL中,特别是在干旱季节,观察到同位素稳态存在较大偏差。相比之下,C3树银杏分枝杆菌的白天Δ18OL接近同位素稳态。在整个数据集中,非稳态预测解释了观测到的Δ18OL变化的49%,而稳态预测仅解释了14%。在雨季期间,当可以将Δ18OL与以C3和CAM模式运行的Clusia个人进行比较时,稳态和非稳态模型就白天Δ18OL的种间变化给出了相反的预测。观察到的Δ18OL模式与非稳态预测的模式匹配。结果提供了一个清晰的例子,说明叶水18O动力学的非稳态控制如何使蒸腾速率与日间Δ18OL之间的关系的斜率从负变为正。

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