School of Life and Environmental Sciences, The University of Sydney, 380 Werombi Road, Brownlow Hill, NSW, 2570, Australia.
School of Life Sciences and Oceanography, Shenzhen University, 3688 Nanhai Ave, Shenzhen, Guangdong, 518060, China.
Photosynth Res. 2019 Jul;141(1):65-82. doi: 10.1007/s11120-019-00622-z. Epub 2019 Feb 15.
The temperature response of mesophyll conductance to CO diffusion (g) has been shown to vary considerably between species but remains poorly understood. Here, we tested the hypothesis that increases in chloroplast surface area with increasing temperature, due to the formation of chloroplast protrusions, caused observed positive responses of g to temperature. We found no evidence of chloroplast protrusions. Using simultaneous measurements of carbon and oxygen isotope discrimination during photosynthesis to separate total g (g) into cell wall and plasma membrane conductance (g) and chloroplast membrane conductance (g) components, we explored the temperature response in genotypes of soybean and barley, and sunflower plants grown at differing CO concentrations. Differences in the temperature sensitivity of g were found between genotypes and between plants grown at differing CO concentration but did not relate to measured anatomical features such as chloroplast surface area or cell wall thickness. The closest fit of modelled g to estimated values was found when cell wall thickness was allowed to decline at higher temperatures and transpiration rates, but it remains to be tested if this decline is realistic. The temperature response of g (calculated from the difference between 1/g and 1/g) varied between barley genotypes, and was best fitted by an optimal response in sunflower. Taken together, these results indicate that g is a highly complex trait with unpredictable sensitivity to temperature that varies between species, between genotypes within a single species, with growth environment, between replicate leaves, and even with age for an individual leaf.
叶片胞间导度对 CO 扩散的温度响应（g）在不同物种间变化很大，但仍知之甚少。在这里，我们检验了一个假设，即由于叶绿体突起的形成，叶绿体表面积随温度升高而增加，导致 g 对温度的正向响应。我们没有发现叶绿体突起的证据。我们使用光合作用过程中碳和氧同位素分馏的同时测量，将总 g（g）分为细胞壁和质膜导度（g）和叶绿体膜导度（g）组分，在不同 CO 浓度下生长的大豆和大麦以及向日葵植物的基因型中探索温度响应。在不同基因型和不同 CO 浓度下生长的植物之间发现了 g 的温度敏感性差异，但与测量的解剖特征（如叶绿体表面积或细胞壁厚度）无关。当允许细胞壁厚度在较高温度和蒸腾速率下下降时，模型化的 g 与估计值的拟合最为接近，但仍有待检验这种下降是否现实。g 的温度响应（通过 1/g 和 1/g 之间的差异计算得出）在大麦基因型之间存在差异，在向日葵中最佳拟合为最优响应。总的来说，这些结果表明，g 是一个高度复杂的特征，对温度的敏感性不可预测，在不同物种之间、同一物种内的不同基因型之间、生长环境之间、重复叶片之间，甚至在单个叶片的年龄之间都存在差异。
