Temperature response of carbon isotope discrimination and mesophyll conductance in tobacco
Temperature response of carbon isotope discrimination and mesophyll conductance in tobacco
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DOI：
10.1111/j.1365-3040.2012.02591.x
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发表时间：
2013-04-01
影响因子：
7.3
通讯作者：
Von Caemmerer, Susanne
中科院分区：
文献类型：
--
作者：
Evans, John R.;Von Caemmerer, Susanne
叶绿体内羧基化位点的CO2分压取决于CO2从胞间空间向羧基化位点扩散的传导，称为叶肉传导（mesophyl conductivity, gm）。本研究利用可调谐二极管激光光谱技术，结合强光下的气体交换、环境CO2浓度为2或21%，以及碳同位素测量，研究了烟草（Nicotiana tabacum）中转基因的温度响应。在O2浓度为2%或21%时，gm随温度线性增加。在21% O2条件下，随着温度从15℃升高到40℃，与gm相关的同位素识别从5.0 +/- 0.2‰下降到1.8 +/- 0.2‰，但光呼吸对同位素信号的贡献是显著的。虽然光呼吸的分异因子（f=16.2 +/- 0.7 ppm）与20至35℃之间的温度无关，但与光呼吸相关的分异因子在15至40℃之间从1.1 +/- 0.01增加到2.7 +/- 0.02 ppm。其他线粒体呼吸作用的分异因子约为0.2 +/- 0.03 ppm。从环境空气到胞间空气的CO2分压下降几乎与叶温无关。相比之下，随着叶温的升高，gm的增加导致细胞间隙和羧基化位点之间的CO2分压在高温下大幅下降。
The partial pressure of CO2 at the sites of carboxylation within chloroplasts depends on the conductance to CO2 diffusion from intercellular airspace to the sites of carboxylation, termed mesophyll conductance (gm). We investigated the temperature response of gm in tobacco (Nicotiana tabacum) by combining gas exchange in high light, ambient CO2 in either 2 or 21% O2 with carbon isotope measurements using tuneable diode laser spectroscopy. The gm increased linearly with temperature in 2 or 21% O2. In 21% O2, isotope discrimination associated with gm decreased from 5.0 +/- 0.2 to 1.8 +/- 0.2 parts per thousand as temperature increased from 15 to 40 degrees C, but the photorespiratory contribution to the isotopic signal is significant. While the fractionation factor for photorespiration (f=16.2 +/- 0.7 parts per thousand) was independent of temperature between 20 and 35 degrees C, discrimination associated with photorespiration increased from 1.1 +/- 0.01 to 2.7 +/- 0.02 parts per thousand from 15 to 40 degrees C. Other mitochondrial respiration contributed around 0.2 +/- 0.03 parts per thousand. The drawdown in CO2 partial pressure from ambient air to intercellular airspaces was nearly independent of leaf temperature. By contrast, the increase in gm with increasing leaf temperature resulted in the drawdown in CO2 partial pressure between intercellular airspaces and the sites of carboxylation decreasing substantially at high temperature.