Microelement Research Center, Huazhong Agricultural University, Wuhan, China.
Key Laboratory of Arable Land Conservation (Middle and Lower Reaches of Yangtze River), Ministry of Agriculture and Rural Affairs, Wuhan, China.
Plant Cell Environ. 2022 Oct;45(10):2987-3000. doi: 10.1111/pce.14405. Epub 2022 Aug 12.
Leaf growth relies on photosynthesis and hydraulics to provide carbohydrates and expansion power; in turn, leaves intercept light and construct organism systems for functioning. Under potassium (K) deficiency stress, leaf area, photosynthesis and hydraulics are all affected by alterations in leaf structure. However, the connection between changes in leaf growth and function caused by the structure under K regulation is unclear. Consequently, the leaf hydraulic conductance (K ) and photosynthetic rate (A) combined with leaf anatomical characteristics of Brassica napus were continuously observed during leaf growth under different K supply levels. The results showed that K and A decreased simultaneously after leaf area with the increasing K deficiency stress. K deficiency significantly increased longitudinal mesophyll cell investment, leading to a reduced volume fraction of intercellular air-space (f ) and decreased leaf expansion rate. Furthermore, reduced f decreased mesophyll and chloroplast surfaces exposed to intercellular airspace and gas phase H O transport, which induced coordinated changes in CO mesophyll conductance and hydraulic conductance in extra-xylem pathways. Adequate K supply facilitated higher f through smaller palisade tissue cell density (loose mesophyll cell arrangement) and smaller spongy tissue cell size, which coordinated CO and H O conductance and promoted leaf area expansion.
叶片生长依赖光合作用和水力来提供碳水化合物和扩展动力；反过来，叶片拦截光并构建生物体系统以发挥功能。在钾（K）缺乏胁迫下，叶片面积、光合作用和水力都会受到叶片结构变化的影响。然而，K 调节下结构变化引起的叶片生长和功能变化之间的联系尚不清楚。因此，在不同的 K 供应水平下，连续观察了甘蓝型油菜叶片生长过程中叶片水力传导率（K）和光合速率（A）与叶片解剖学特征的关系。结果表明，随着 K 缺乏胁迫的增加，叶片面积增大后 K 和 A 同时下降。K 缺乏显著增加了纵向叶肉细胞的投入，导致细胞间空气空间的体积分数（f）降低，叶片扩展率降低。此外，f 的降低减少了暴露于细胞间空气空间和气相 H2O 传输的叶肉和叶绿体表面，从而诱导了非木质部途径中 CO2 叶肉导度和水力导度的协调变化。充足的 K 供应通过较小的栅状组织细胞密度（疏松的叶肉细胞排列）和较小的海绵组织细胞大小促进了更高的 f，从而协调了 CO2 和 H2O 导度，促进了叶片面积的扩展。
