Department of Medical Biochemistry and Biophysics, Umeå University, Umeå, Sweden.
Department of Forest Ecology and Management, Swedish University of Agricultural Sciences, Umeå, Sweden.
Plant Cell Environ. 2021 Jun;44(6):1756-1768. doi: 10.1111/pce.14043. Epub 2021 Mar 29.
Sphagnum mosses account for most accumulated dead organic matter in peatlands. Therefore, understanding their responses to increasing atmospheric CO is needed for estimating peatland C balances under climate change. A key process is photorespiration: a major determinant of net photosynthetic C assimilation that depends on the CO to O ratio. We used climate chambers to investigate photorespiratory responses of Sphagnum fuscum hummocks to recent increases in atmospheric CO (from 280 to 400 ppm) under different water table, temperature, and light intensity levels. We tested the photorespiratory variability using a novel method based on deuterium isotopomers (D6 /D6 ratio) of photosynthetic glucose. The effect of elevated CO on photorespiration was highly dependent on water table. At low water table (-20 cm), elevated CO suppressed photorespiration relative to C assimilation, thus substantially increasing the net primary production potential. In contrast, a high water table (0 cm) favored photorespiration and abolished this CO effect. The response was further tested for Sphagnum majus lawns at typical water table levels (0 and -7 cm), revealing no effect of CO under those conditions. Our results indicate that hummocks, which typically experience low water table levels, benefit from the 20th century's increase in atmospheric CO .
泥炭地中积累的大部分有机死物质来自于泥炭藓。因此，为了估算气候变化下泥炭地碳平衡，需要了解其对大气 CO 浓度增加的响应。其中一个关键过程是光呼吸：这是净光合碳同化的主要决定因素，取决于 CO 与 O 的比例。我们使用气候室，在不同的地下水位、温度和光照强度水平下，研究了大气 CO（从 280 ppm 增加到 400 ppm）对藓类泥炭藓丘光呼吸的影响。我们使用一种基于光合作用葡萄糖的氘同位素（D6 / D6 比）的新方法来测试光呼吸的可变性。CO 升高对光呼吸的影响高度依赖于地下水位。在低地下水位（-20 厘米）下，与碳同化相比，高 CO 抑制了光呼吸，从而大大增加了净初级生产力的潜力。相比之下，高地下水位（0 厘米）有利于光呼吸，并消除了这种 CO 效应。在典型地下水位水平（0 和-7 厘米）下，对泥炭藓草坪进行了进一步测试，在这些条件下 CO 没有影响。我们的结果表明，通常经历低地下水位的泥炭藓丘受益于 20 世纪大气 CO 的增加。
