Teskey R O, McGuire M A
University of Georgia, Athens, GA 30602, USA.
Plant Cell Environ. 2007 May;30(5):570-9. doi: 10.1111/j.1365-3040.2007.01649.x.
CO(2) released by respiring cells in tree stems can either diffuse to the atmosphere or dissolve in xylem sap. In this study, the internal and external fluxes of CO(2) released from respiring stems of five sycamore (Platanus occidentalis L.) trees were calculated. Mean rates of stem respiration were highest in mid-afternoon and lowest at night, and were positively correlated with air temperature. Over a 24 h period, on average 34% of the CO(2) released by respiring cells in the measured stem segment remained within the tree. CO(2) efflux to the atmosphere consisted of similar proportions of CO(2) derived from local respiring cells (55%) and CO(2) that had been transported in the xylem (45%), indicating that CO(2) efflux does not accurately estimate respiration. A portion of the efflux of transported CO(2) appeared to have originated in the root system. A modification of the method for calculating stem respiration based on internal and external fluxes of CO(2) was developed to separate efflux due to local respiration from efflux of transported CO(2).
树木茎干中进行呼吸作用的细胞释放出的二氧化碳（CO₂），既可以扩散到大气中，也可以溶解在木质部汁液中。在本研究中，计算了五株美国梧桐（Platanus occidentalis L.）树木呼吸茎干释放的二氧化碳的内部和外部通量。茎干呼吸的平均速率在午后最高，夜间最低，且与气温呈正相关。在24小时内，所测茎段中进行呼吸作用的细胞释放的二氧化碳平均有34%保留在树木内部。向大气的二氧化碳排放通量中，来自局部呼吸细胞的二氧化碳（55%）和通过木质部运输的二氧化碳（45%）比例相近，这表明二氧化碳排放通量并不能准确估算呼吸作用。一部分运输的二氧化碳排放通量似乎起源于根系。基于二氧化碳的内部和外部通量，开发了一种计算茎干呼吸作用的方法的改进版本，以区分局部呼吸产生的排放通量和运输的二氧化碳的排放通量。
