Effect of high light on canopy-level photosynthesis and leaf mesophyll ion flux in tomato
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ORIGINAL ARTICLE
Effect of high light on canopy‑level photosynthesis and leaf mesophyll ion flux in tomato Mohammad Hossain Babla1 · David Thomas Tissue2 · Christopher Ian Cazzonelli2 · Zhong‑Hua Chen1,2 Received: 27 September 2020 / Accepted: 5 October 2020 © Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract Main conclusion This study highlights the potential link between high light-induced canopy-level photosynthesis and mesophyll cell K+, Cl−, Ca2+, and H+ homeostasis in tomato. Abstract 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 Ca2+ 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 Ca2+ 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. Keywords Electrophysiology · Gas exchange · Leaf mesophyll · Light intensity · Solanum lycopersicum L. · Stress response
Introduction
Communicated by Anastasios Melis. Electronic supplementary material The online version of this article (https://doi.org/10.1007/s00425-020-03493-0) contains supplementary material, which is available to authorized users. * Zhong‑Hua Chen [email protected] 1
School of Science, Western Sydney University, Penrith, NSW 2751, Australia
Hawkesbury Institute for the Environment, Western Sydney University, Penrith, NSW 2751, Australia
2
Light is one of the important environmental cues for plant growth. Refined sensing and response to the intensity, direction, duration, and wavelength of light are essential to plants (Fankhauser and Chory 1997; Babla et
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