Unsaturation of vapour pressure inside leaves of two conifer species.
Unsaturation of vapour pressure inside leaves of two conifer species.
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DOI：
10.1038/s41598-018-25838-2
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发表时间：
2018-05-16
影响因子：
4.6
通讯作者：
Farquhar GD
中科院分区：
文献类型：
--
作者：
Cernusak LA;Ubierna N;Jenkins MW;Garrity SR;Rahn T;Powers HH;Hanson DT;Sevanto S;Wong SC;McDowell NG;Farquhar GD
气孔导度（gs）影响光合作用和蒸腾作用，因此对全球碳和水循环、粮食生产和生态系统服务至关重要。数学模型提供了分析这一重要叶片气体交换参数的主要手段。在这些模型中，一个几乎普遍的假设是，在所有条件下，树叶内部的蒸气压（ei）都保持饱和。这一假设的有效性还没有得到很好的检验，因为到目前为止还不能直接测量。在这里，我们使用一种新技术来验证这一假设，该技术基于叶片气体交换和通过叶片的二氧化碳和水蒸气的稳定同位素组成的耦合测量。我们将此技术应用于两种半干旱针叶树的成熟个体。在这两个物种中，当叶片暴露于中等到高的空气蒸气压赤字时，ei通常下降到饱和以下。单种刺柏（Juniperus monosperma）和毛松（Pinus edulis）胞间相对湿度的典型值分别为0.9和0.8。这些ei与饱和度的偏离在计算gs和细胞间CO2浓度时造成了显著的偏差。我们的结果驳斥了长期以来在所有条件下植物叶片中饱和蒸汽压的假设。
Stomatal conductance (gs) impacts both photosynthesis and transpiration, and is therefore fundamental to the global carbon and water cycles, food production, and ecosystem services. Mathematical models provide the primary means of analysing this important leaf gas exchange parameter. A nearly universal assumption in such models is that the vapour pressure inside leaves (ei) remains saturated under all conditions. The validity of this assumption has not been well tested, because so far ei cannot be measured directly. Here, we test this assumption using a novel technique, based on coupled measurements of leaf gas exchange and the stable isotope compositions of CO2 and water vapour passing over the leaf. We applied this technique to mature individuals of two semiarid conifer species. In both species, ei routinely dropped below saturation when leaves were exposed to moderate to high air vapour pressure deficits. Typical values of relative humidity in the intercellular air spaces were as low 0.9 in Juniperus monosperma and 0.8 in Pinus edulis. These departures of ei from saturation caused significant biases in calculations of gs and the intercellular CO2 concentration. Our results refute the longstanding assumption of saturated vapour pressure in plant leaves under all conditions.
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影响因子：
7.4
作者：
FARQUHAR, GD;RASCHKE, K
通讯作者：
RASCHKE, K
影响因子：
6.9
作者：
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通讯作者：
Boyer JS
影响因子：
6.2
作者：
Bowling, DR;Sargent, SD;Ehleringer, JR
通讯作者：
Ehleringer, JR
影响因子：
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作者：
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影响因子：
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作者：
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