Plant shoots can act as sources or sinks of trace gases including methane and nitrous oxide. Accurate measurements of these trace gas fluxes require enclosing of shoots in closed non-steady-state chambers. Due to plant physiological activity, this type of enclosure, however, leads to CO₂ depletion in the enclosed air volume, condensation of transpired water, and warming of the enclosures exposed to sunlight, all of which may bias the flux measurements. Here, we present ShoTGa-FluMS (SHOot Trace Gas FLUx Measurement System), a novel measurement system designed for continuous and automated measurements of trace gas and volatile organic compound (VOC) fluxes from plant shoots. The system uses transparent shoot enclosures equipped with Peltier cooling elements and automatically replaces fixated CO₂ and removes transpired water from the enclosure. The system is designed for measuring trace gas fluxes over extended periods, capturing diurnal and seasonal variations, and linking trace gas exchange to plant physiological functioning and environmental drivers. Initial measurements show daytime CH₄ emissions of two pine shoots of 0.056 and 0.089 nmol per gram of foliage dry weight (d.w.) per hour or 7.80 and 13.1 $\mathrm{nmol}{\mathrm{m}}^{-\mathrm{2}}{\mathrm{h}}^{-\mathrm{1}}$. Simultaneously measured CO₂ uptake rates were 9.2 and 7.6 $\mathrm{mmol}{\mathrm{m}}^{-\mathrm{2}}{\mathrm{h}}^{-\mathrm{1}}$, and transpiration rates were 1.24 and 0.90 $\mathrm{mol}{\mathrm{m}}^{-\mathrm{2}}{\mathrm{h}}^{-\mathrm{1}}$. Concurrent measurement of VOC emissions demonstrated that potential effects of spectral interferences on CH₄ flux measurements were at least 10-fold smaller than the measured CH₄ fluxes. Overall, this new system solves multiple technical problems that have so far prevented automated plant shoot trace gas flux measurements and holds the potential for providing important new insights into the role of plant foliage in the global CH₄ and N₂O cycles.

中文翻译：

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用于从植物叶子和其他植物隔间进行痕量气体通量测量的自动化系统

植物芽可以作为包括甲烷和一氧化二氮在内的痕量气体的来源或汇。这些痕量气体通量的准确测量需要将芽封闭在封闭的非稳态室中。然而，由于植物的生理活动，这种类型的外壳会导致封闭空气体积中的CO ₂消耗、蒸发水的冷凝以及暴露在阳光下的外壳变暖，所有这些都可能使通量测量产生偏差。在这里，我们介绍ShoTGa-FluMS（SHOot Trace Gas FLUx 测量系统），一种新型测量系统，设计用于连续和自动测量来自植物芽的痕量气体和挥发性有机化合物 (VOC) 通量。该系统使用配备有 Peltier 冷却元件的透明拍摄外壳，并自动替换固定的CO ₂并从外壳中去除蒸发的水。该系统设计用于长时间测量微量气体通量，捕捉昼夜和季节变化，并将微量气体交换与植物生理功能和环境驱动因素联系起来。初步测量显示，两个松枝的白天CH ₄排放量为 0.056 和 0.089  nmol每克树叶干重 (dw) 每小时或 7.80 和 13.1 $\mathrm{毫摩尔}{\mathrm{米}}^{——\mathrm{2}}{\mathrm{H}}^{——\mathrm{1}}$. 同时测得的CO ₂吸收率分别为 9.2 和 7.6 $\mathrm{毫摩尔}{\mathrm{米}}^{——\mathrm{2}}{\mathrm{H}}^{——\mathrm{1}}$, 蒸腾速率分别为 1.24 和 0.90 $\mathrm{摩尔}{\mathrm{米}}^{——\mathrm{2}}{\mathrm{H}}^{——\mathrm{1}}$. 对 VOC 排放的同时测量表明，光谱干扰对CH ₄通量测量的潜在影响比测量的CH ₄通量小至少 10 倍。总体而言，这个新系统解决了迄今为止阻止自动植物芽痕量气体通量测量的多个技术问题，并有可能为植物叶子在全球CH ₄和N ₂ O循环中的作用提供重要的新见解。