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Front. Plant Sci. | doi: 10.3389/fpls.2018.01739

Elevated CO2 improves photosynthesis under high temperature by attenuating the functional limitations to energy fluxes, electron transport and redox homeostasis in tomato leaves

  • 1Zhejiang University, China
  • 2Henan University of Science and Technology, China
  • 3Tea Research Institute (CAAS), China

Elevated atmospheric CO2 improves leaf photosynthesis and plant tolerance to heat stress, however, the underlying mechanisms remain unclear. In this study, we exposed tomato plants to elevated CO2 (800 µmol mol-1) and/or high temperature ( 42 °C for 24 h), and examined a range of photosynthetic and chlorophyll fluorescence parameters as well as cellular redox state to better understand the response of photosystem II (PSII) and PSI to elevated CO2 and heat stress. The results showed that, while the heat stress drastically decreased the net photosynthetic rate (Pn), maximum carboxylation rate (Vcmax), maximum ribulose-1,5-bis-phosphate (RuBP) regeneration rate (Jmax) and maximal photochemical efficiency of PSII (Fv/Fm), the elevated CO2 improved those parameters under heat stress and at a 24 h recovery. Furthermore, the heat stress decreased the absorption flux, trapped energy flux, electron transport, energy dissipation per PSII cross section, while the elevated CO2 had the opposing effects that eventually decreased photoinhibition, damage to photosystems and reactive oxygen species accumulation. Similarly, the elevated CO2 helped the plants to maintain a reduced redox state as evidenced by the increased ratios of ASA:DHA and GSH:GSSG under heat stress and at recovery. Furthermore, the concentration of NADP+ and ratio of NADP+ to NADPH were induced by elevated CO2 at recovery. This study unraveled the crucial mechanisms of elevated CO2-mediated changes in energy fluxes, electron transport and redox homeostasis under heat stress, and shed new light on the responses of tomato plants to combined heat and elevated CO2.

Keywords: Heat stress, elevated CO2, Chlorophyll fluorescence transient, redox, Electron Transport, Tomato

Received: 05 Aug 2018; Accepted: 08 Nov 2018.

Edited by:

Marian Brestic, Slovak University of Agriculture, Slovakia

Reviewed by:

Parvaiz Ahmad, Sri Pratap College Srinagar, India
Basharat Ali, Universität Bonn, Germany  

Copyright: © 2018 Pan, Ahammed, Li and Shi. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.

* Correspondence: Dr. Golam Jalal Ahammed, Henan University of Science and Technology, Luoyang, China, ahammed@haust.edu.cn