Jahan Eisrat, Sharwood Robert Edward, Tissue David T
School of Life and Environmental Sciences, The University of Sydney, Camden, NSW, Australia.
Hawkesbury Institute for the Environment, Western Sydney University, Hawksbury, Penrith, NSW, Australia.
Front Plant Sci. 2023 Jun 20;14:1091418. doi: 10.3389/fpls.2023.1091418. eCollection 2023.
statement: Mesophyll conductance ( ) was negatively correlated with wheat leaf age but was positively correlated with the surface area of chloroplasts exposed to intercellular airspaces ( ). The rate of decline in photosynthetic rate and as leaves aged was slower for water-stressed than well-watered plants. Upon rewatering, the degree of recovery from water-stress depended on the age of the leaves, with the strongest recovery for mature leaves, rather than young or old leaves. Diffusion of CO from the intercellular airspaces to the site of Rubisco within C plant chloroplasts () governs photosynthetic CO assimilation (). However, variation in in response to environmental stress during leaf development remains poorly understood. Age-dependent changes in leaf ultrastructure and potential impacts on , , and stomatal conductance to CO ( ) were investigated for wheat ( L.) in well-watered and water-stressed plants, and after recovery by re-watering of droughted plants. Significant reductions in and were found as leaves aged. The oldest plants (15 days and 22 days) in water-stressed conditions showed higher A and gm compared to irrigated plants. The rate of decline in and as leaves aged was slower for water-stressed compared to well-watered plants. When droughted plants were rewatered, the degree of recovery depended on the age of the leaves, but only for . The surface area of chloroplasts exposed to intercellular airspaces ( ) and the size of individual chloroplasts declined as leaves aged, resulting in a positive correlation between and . Leaf age significantly affected cell wall thickness ( ), which was higher in old leaves compared to mature/young leaves. Greater knowledge of leaf anatomical traits associated with partially explained changes in physiology with leaf age and plant water status, which in turn should create more possibilities for improving photosynthesis using breeding/biotechnological strategies.
叶肉导度（ ）与小麦叶片年龄呈负相关，但与暴露于细胞间隙的叶绿体表面积（ ）呈正相关。水分胁迫下的植物叶片衰老时，光合速率和 的下降速率比水分充足的植物慢。复水后，水分胁迫的恢复程度取决于叶片年龄，成熟叶片的恢复最强，而非幼叶或老叶。在C4植物叶绿体（ ）中，CO2从细胞间隙扩散到Rubisco作用位点，这一过程控制着光合CO2同化（ ）。然而，叶片发育过程中 对环境胁迫的响应变化仍知之甚少。研究了水分充足和水分胁迫的小麦（ L.）植株，以及干旱植株复水后的叶片超微结构随年龄的变化及其对 、 和气孔导度（ ）的潜在影响。随着叶片衰老， 和 显著降低。水分胁迫条件下最老的植株（15天和22天）与灌溉植株相比，显示出更高的A和gm。与水分充足的植物相比，水分胁迫下叶片衰老时 和 的下降速率较慢。当干旱植株复水时，恢复程度取决于叶片年龄，但仅针对 。随着叶片衰老，暴露于细胞间隙的叶绿体表面积（ ）和单个叶绿体的大小下降，导致 和 之间呈正相关。叶片年龄显著影响细胞壁厚度（ ），老叶的细胞壁厚度高于成熟/幼叶。对与 相关的叶片解剖特征有更多了解，部分解释了叶片年龄和植物水分状况对生理的影响变化，这反过来应该为利用育种/生物技术策略改善光合作用创造更多可能性。
