Sensitivity of infrared water vapor analyzers to oxygen concentration and errors in stomatal conductance
Sensitivity of infrared water vapor analyzers to oxygen concentration and errors in stomatal conductance
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DOI：
10.1023/a:1015529909457
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发表时间：
2002-01-01
影响因子：
3.7
通讯作者：
Bunce, JA
中科院分区：
文献类型：
--
作者：
Bunce, JA
在光合作用系统中使用红外分析仪测量水蒸气浓度正变得越来越普遍。众所周知，红外二氧化碳和水蒸气分析仪的灵敏度受背景气体中的氧浓度的影响，特别是对于绝对分析仪，但由于氧浓度对红外水蒸气分析仪灵敏度的影响，气孔导度估计中的大误差的可能性没有得到广泛认可。本工作测试了三种类型的红外水汽分析仪的灵敏度变化取决于背景气体的氧含量。结果发现，改变从0或2%到21%的氮气中的氧降低约4%的灵敏度，所有三种类型的红外水汽分析仪的水汽。灵敏度的变化与氧摩尔分数呈线性关系。计算气孔导度的误差主要取决于叶片与空气的水汽压差和叶片温度，也取决于叶片温度是直接测量的还是通过能量平衡计算的。温室条件下大豆叶片气体交换的测量结果表明，从21%到2%的氧气变化产生了一个人为的气孔导度，平均约30%的明显增加。湿滤纸的“电导”也出现类似的误差。这种错误可能会影响光合作用对氧气的敏感性依赖于二氧化碳的推论。
Use of infrared analyzers to measure water vapor concentrations in photosynthesis systems is becoming common. It is known that sensitivity of infrared carbon dioxide and water vapor analyzers is affected by the oxygen concentration in the background gas, particularly for absolute analyzers, but the potential for large errors in estimates of stomatal conductance due to effects of oxygen concentration on the sensitivity of infrared water vapor analyzers is not widely recognized. This work tested three types of infrared water vapor analyzers for changes in sensitivity of infrared water vapor analyzers depending on the oxygen content of the background gas. It was found that changing from either 0 or 2% to 21% oxygen in nitrogen decreased the sensitivity to water vapor for all three types of infrared water vapor analyzers by about 4%. The change in sensitivity was linear with oxygen mole fraction. The resulting error in calculated stomatal conductance would depend strongly on the leaf to air vapor pressure difference and leaf temperature, and also on whether leaf temperature was directly measured or calculated from energy balance. Examples of measurements of gas exchange on soybean leaves under glasshouse conditions indicated that changing from 21% to 2% oxygen produced an artifactual apparent increase in stomatal conductance which averaged about 30%. Similar errors occurred for `conductances' of wet filter paper. Such errors could affect inferences about the carbon dioxide dependence of the sensitivity of photosynthesis to oxygen.