Post‐illumination transient O2‐uptake is driven by photorespiration in tobacco leaves

• Published in: Physiologia plantarum 2016-02, Vol.156 (2), p.227-238
• Main Authors: Sejima, Takehiro, Hanawa, Hitomi, Shimakawa, Ginga, Takagi, Daisuke, Suzuki, Yuji, Fukayama, Hiroshi, Makino, Amane, Miyake, Chikahiro
• Format: Article
• Language: English
• Subjects: adenosine triphosphate; C3 plants; C4 plants; Carbon dioxide; Chlorophyll; corn; Fluorescence; Leaves; lighting; Nicotiana tabacum; oxygen; photorespiration; Photosynthesis; photosystem II; Plants; ribulose 1,5-diphosphate; Tobacco
• ISSN: 0031-9317; 1399-3054
• DOI: 10.1111/ppl.12388

This study aims to elucidate the molecular mechanism for the transient increase in the O₂‐uptake rate in tobacco (Nicotiana tabacum cv Xanthi) leaves after turning off actinic lights (ALs). The photosynthetic O₂ evolution rate reaches a maximum shortly after the onset of illumination with ALs and then decreases to zero in atmospheric CO₂/O₂ conditions. After turning off the ALs, tobacco leaves show a transient increase in the O₂‐uptake rate, the post‐illumination transient O₂‐uptake, and thereafter, the O₂‐uptake rate decreases to the level of the dark‐respiration rate. Photosynthetic linear electron flow, evaluated as the quantum yield of photosystem II [Y(II)], maintained a steady‐state value distinct from the photosynthetic O₂‐evolution rate. In high‐[CO₂] conditions, the photosynthetic O₂‐evolution rate and Y(II) showed a parallel behavior, and the post‐illumination transient O₂‐uptake was suppressed. On the other hand, in maize leaves (a C4 plant), even in atmospheric CO₂/O₂ conditions, Y(II) paralleled the photosynthetic O₂‐evolution rate and the post‐illumination transient O₂‐uptake was suppressed. Hypothesizing that the post‐illumination transient O₂‐uptake is driven by C3 plant photorespiration in tobacco leaves, we calculated both the ribulose 1,5‐bisphosphate carboxylase‐ and oxygenase‐rates (Vc and Vo) from photosynthetic O₂‐evolution and the post‐illumination transient O₂‐uptake rates. These values corresponded to those estimated from simultaneous chlorophyll fluorescence/O₂‐exchange analysis. Furthermore, the H⁺‐consumption rate for ATP synthesis in both photosynthesis and photorespiration, calculated from both Vc and Vo that were estimated from chlorophyll fluorescence/CO₂‐exchange analysis, showed a positive linear relationship with the dissipation rate of the electrochromic shift signal. Thus, these findings support our hypothesis.