Functional relationships between hydraulic traits and the timing of diurnal depression of photosynthesis
Functional relationships between hydraulic traits and the timing of diurnal depression of photosynthesis
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DOI：
10.1111/pce.13512
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发表时间：
2019-05-01
影响因子：
7.3
通讯作者：
Scholz, Fabian G.
中科院分区：
文献类型：
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作者：
Bucci, Sandra J.;Carbonell Silletta, Luisina M.;Scholz, Fabian G.
水的协调沿着水的运输途径，帮助树木提供足够的水供应冠层，确保水分亏缺最小化，气孔保持开放的CO2吸收。我们评估了安第斯山脉南部七种万年青树种的茎和叶的水力协调以及水力特征与光合作用日抑制时间之间的联系。茎导水率（k（s））与叶导水率（K-Leaf）在物种间存在正相关关系。所有物种的最大光合速率（A（max））相似。具有较高k（s）和K-Leaf的物种在上午达到A（max），而具有较低k（s）和K-Leaf的物种在下午早些时候同时出现膨压损失。后者的物种有非常负的叶水势，但远离的压力，在该压力下的88%的叶水力传导损失。我们的研究结果表明，昼夜气体交换动态可能是由叶片水力脆弱性，使一个物种更容易受到干旱限制水分流失和碳同化早于物种不那么脆弱。然而，在较强的干旱下，具有较早CO2吸收抑制的物种可能会增加水力失效的风险，因为它们的安全裕度相对较窄。
The hydraulic coordination along the water transport pathway helps trees provide adequate water supply to the canopy, ensuring that water deficits are minimized and that stomata remain open for CO2 uptake. We evaluated the stem and leaf hydraulic coordination and the linkages between hydraulic traits and the timing of diurnal depression of photosynthesis across seven evergreen tree species in the southern Andes. There was a positive correlation between stem hydraulic conductivity (k(s)) and leaf hydraulic conductance (K-Leaf) across species. All species had similar maximum photosynthetic rates (A(max)). The species with higher k(s) and K-Leaf attained A(max) in the morning, whereas the species with lower k(s) and K-Leaf exhibited their A(max) in the early afternoon concurrently with turgor loss. These latter species had very negative leaf water potentials, but far from the pressure at which the 88% of leaf hydraulic conductance is lost. Our results suggest that diurnal gas exchange dynamics may be determined by leaf hydraulic vulnerability such that a species more vulnerable to drought restrict water loss and carbon assimilation earlier than species less vulnerable. However, under stronger drought, species with earlier CO2 uptake depression may increase the risk of hydraulic failure, as their safety margins are relatively narrow.