Yang Ying-Jie, Hu Hong, Huang Wei
Kunming Institute of Botany, Chinese Academy of Sciences, Kunming 650201, China.
University of Chinese Academy of Sciences, Beijing 100049, China.
Plants (Basel). 2020 Nov 10;9(11):1536. doi: 10.3390/plants9111536.
Mesophyll conductance () limits CO diffusion from sub-stomatal internal cavities to the sites of RuBP carboxylation. However, the response of to light intensity remains controversial. Furthermore, little is known about the light response of relative mesophyll conductance limitation () and its effect on photosynthesis. In this study, we measured chlorophyll fluorescence and gas exchange in nine evergreen sclerophyllous species. was maintained stable across light intensities from 300 to 1500 μmol photons m s in all these species, indicating that did not respond to the change in illumination in them. With an increase in light intensity, gradually increased, making the major limiting factor for area-based photosynthesis () under saturating light. A strong negative relationship between and was found at 300 μmol photons m s but disappeared at 1500 μmol photons m s, suggesting an important role for in determining at sub-saturating light. Furthermore, the light-dependent increase in led to a decrease in chloroplast CO concentration (), inducing the gradual increase of photorespiration. A higher under saturating light made more limited by RuBP carboxylation. These results indicate that the light response of plays significant roles in determining , photorespiration, and the rate-limiting step of .
叶肉导度（）限制了二氧化碳从气孔下内腔向核酮糖-1,5-二磷酸羧化位点的扩散。然而，叶肉导度对光强的响应仍存在争议。此外，关于相对叶肉导度限制（）的光响应及其对光合作用的影响知之甚少。在本研究中，我们测量了9种常绿硬叶植物的叶绿素荧光和气体交换。在所有这些物种中，叶肉导度在300至1500 μmol光子·m⁻²·s⁻¹的光强范围内保持稳定，这表明叶肉导度对它们光照变化没有响应。随着光强增加，逐渐增加，使得在饱和光强下成为基于叶面积的光合作用（）的主要限制因素。在300 μmol光子·m⁻²·s⁻¹时发现与之间存在强烈的负相关关系，但在1500 μmol光子·m⁻²·s⁻¹时消失，这表明在亚饱和光强下对的确定具有重要作用。此外，光强依赖的增加导致叶绿体二氧化碳浓度（）降低，从而诱导光呼吸逐渐增加。在饱和光强下较高的使得更多地受到核酮糖-1,5-二磷酸羧化的限制。这些结果表明叶肉导度的光响应在确定、光呼吸和的限速步骤中起重要作用。
