School of Science, Western Sydney University, Penrith, NSW, 2751, Australia.
Hawkesbury Institute for the Environment, Western Sydney University, Penrith, NSW, 2751, Australia.
Planta. 2020 Oct 9;252(5):80. doi: 10.1007/s00425-020-03493-0.
This study highlights the potential link between high light-induced canopy-level photosynthesis and mesophyll cell K, Cl, Ca, and H homeostasis in tomato. Light is a primary energy source for photosynthesis and a vital regulator of mineral nutrient uptake and distribution in plants. Plants need to optimize photosynthesis and nutrient balance in leaves for performance in fluctuating light conditions that are partially regulated by light-induced ion homeostatsis in the mesophyll cells. It is still elusive whether high light-induced leaf mesophyll ion fluxes affect leaf photosynthesis at different canopy levels in Solanum lycopersicum L. Leaf gas exchange and microelectrode ion flux (MIFE) measurements were employed to study the effects of prolonged light-induced canopy-level leaf physiological responses of tomato plants. High light resulted in a significant lowering in photosynthesis in the fully-exposed top canopy leaves of tomato, but not to mid- or low-canopy leaves. Leaf mesophyll K effluxes of all canopies were significantly decreased after three weeks of high light treatment. However, high light-induced leaf mesophyll Ca effluxes were significantly enhanced only in the top and mid canopies. Moreover, we found that photosynthetic parameters were significantly correlated with leaf mesophyll ion fluxes. We thus propose that canopy-level significant Ca efflux and K efflux of leaf mesophyll may serve as early indicators for light-induced regulation on photosynthesis. We conclude that light-induced differential photosynthetic performance and ion fluxes in leaves may implicate a requirement of more uniform light irradiance and spectra at different canopy levels of tall greenhouse tomato plants. This can be achieved through new innovative greenhouse lighting technologies and covering materials towards the enhancement of crop photosynthesis and yield.
本研究强调了高光诱导的冠层水平光合作用与番茄中叶肉细胞 K、Cl、Ca 和 H 内稳态之间的潜在联系。光作为光合作用的主要能源，是植物中矿物质养分吸收和分布的重要调节剂。植物需要在波动的光照条件下优化叶片中的光合作用和养分平衡，部分受叶肉细胞中光诱导的离子内稳态调节。目前尚不清楚高光诱导的叶片叶肉离子通量是否会影响不同冠层水平的叶片光合作用。本研究采用叶片气体交换和微电极离子通量（MIFE）测量来研究番茄植株长时间高光诱导的冠层叶片生理响应的影响。高光导致番茄完全暴露的顶层冠层叶片的光合作用显著降低，但中层和底层叶片不受影响。经过三周的高光处理后，所有冠层的叶片叶肉 K 外排均显著降低。然而，高光仅显著增强了顶层和中层叶片的叶肉 Ca 外排。此外，我们发现光合参数与叶片叶肉离子通量显著相关。因此，我们提出冠层水平显著的 Ca 外排和 K 外排可能是光诱导对光合作用调控的早期指标。我们得出结论，叶片中光诱导的不同光合作用性能和离子通量可能需要在高大棚番茄植株的不同冠层水平上具有更均匀的光照强度和光谱。这可以通过新的创新温室照明技术和覆盖材料来实现，以提高作物的光合作用和产量。
