Variable mesophyll conductance revisited: theoretical background and experimental implications
Variable mesophyll conductance revisited: theoretical background and experimental implications
复制标题
重新审视可变叶肉电导：理论背景和实验意义
DOI：
10.1111/j.1365-3040.2012.02538.x
复制
发表时间：
2012-12-01
影响因子：
7.3
通讯作者：
Zhu, Xin-Guang
中科院分区：
文献类型：
--
作者：
Tholen, Danny;Ethier, Gilbert;Zhu, Xin-Guang
叶绿体基质内羧化位点的CO2浓度不仅取决于气孔导度，还取决于气孔下腔和CO2固定位点之间的CO2电导。这种电导通常称为叶肉电导 (g(m))，显着限制光合作用的速率。在这里，我们表明 g(m) 的估计值受到从线粒体扩散到叶绿体的呼吸和光呼吸 CO2 量的影响。这导致了 g(m) 的明显 CO2 和氧气敏感性，这并不意味着叶肉固有扩散特性的变化，而是取决于线粒体 CO2 释放与叶绿体 CO2 吸收的比率。我们证明，这种效应 (1) 可能会使光照下 CO2 光补偿点和非光呼吸呼吸的估计产生偏差； (2)可影响体内核酮糖1.5-二磷酸羧化酶/加氧酶(Rubisco)动力学常数的估计； (3)导致气孔导度和g(m)之间存在明显的必然相关性。我们进一步表明，通过 Rubisco 重新固定的光（呼吸）CO2 量可以通过 g(m) 的测量直接估计。
The CO2 concentration at the site of carboxylation inside the chloroplast stroma depends not only on the stomatal conductance, but also on the conductance of CO2 between substomatal cavities and the site of CO2 fixation. This conductance, commonly termed mesophyll conductance (g(m)), significantly constrains the rate of photosynthesis. Here we show that estimates of g(m) are influenced by the amount of respiratory and photorespiratory CO2 from the mitochondria diffusing towards the chloroplasts. This results in an apparent CO2 and oxygen sensitivity of g(m) that does not imply a change in intrinsic diffusion properties of the mesophyll, but depends on the ratio of mitochondrial CO2 release to chloroplast CO2 uptake. We show that this effect (1) can bias the estimation of the CO2 photocompensation point and non-photorespiratory respiration in the light; (2) can affect the estimates of ribulose 1.5-bisphosphate carboxylase/oxygenase (Rubisco) kinetic constants in vivo; and (3) results in an apparent obligatory correlation between stomatal conductance and g(m). We further show that the amount of photo(respiratory) CO2 that is refixed by Rubisco can be directly estimated through measurements of g(m).