Plant and Cell Physiology Advance Access originally published online on February 21, 2008
Plant and Cell Physiology 2008 49(4):583-591; doi:10.1093/pcp/pcn030
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The Role of Electron Transport in Determining the Temperature Dependence of the Photosynthetic Rate in Spinach Leaves Grown at Contrasting Temperatures
1Department of Biology, Graduate School of Science, Osaka University, 1-1 Machikaneyama-cho, Toyonaka, Osaka, 560-0043 Japan
2Department of Biological Sciences, Graduate School of Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-0033 Japan
3Department of Life Science, University of Hyogo, 3-2-1 Kamigohri, Ako-Gun, Hyogo, 678-1297 Japan
*Corresponding author: E-mail, wataru.yamori{at}anu.edu.au; Fax, +61-2-6125-5075.
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Abstract |
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The temperature response of the uncoupled whole-chain electron transport rate (ETR) in thylakoid membranes differs depending on the growth temperature. However, the steps that limit whole-chain ETR are still unclear and the question of whether the temperature dependence of whole-chain ETR reflects that of the photosynthetic rate remains unresolved. Here, we determined the whole-chain, PSI and PSII ETR in thylakoid membranes isolated from spinach leaves grown at 30°C [high temperature (HT)] and 15°C [low temperature (LT)]. We measured temperature dependencies of the light-saturated photosynthetic rate at 360 µl l–1 CO2 (A360) in HT and LT leaves. Both of the temperature dependences of whole-chain ETR and of A360 were different depending on the growth temperature. Whole-chain ETR was less than the rates of PSI ETR and PSII ETR in the broad temperature range, indicating that the process was limited by diffusion processes between the PSI and PSII. However, at high temperatures, whole-chain ETR appeared to be limited by not only the diffusion processes but also PSII ETR. The C3 photosynthesis model was used to evaluate the limitations of A360 by whole-chain ETR (Pr) and ribulose bisphosphate carboxylation (Pc). In HT leaves, A360 was co-limited by Pc and Pr at low temperatures, whereas at high temperatures, A360 was limited by Pc. On the other hand, in LT leaves, A360 was solely limited by Pc over the entire temperature range. The optimum temperature for A360 was determined by Pc in both HT and LT leaves. Thus, this study showed that, at low temperatures, the limiting step of A360 was different depending on the growth temperature, but was limited by Pc at high temperatures regardless of the growth temperatures.
Keywords: Electron transport — Photosynthesis — RuBP carboxylation — RuBP regeneration — Temperature acclimation — Temperature dependence
Abbreviations: DBMIB, 5-dibromo-3-methyl-6-isopropyl-p-benzoquinone; DCIP, dichloroindophenol; ETR, electron transport rate; FBPase, fructose-1,6-bisphosphatase; HT, high temperature; LT, low temperature; RuBP, ribulose bisphosphate.
4Present address: Molecular Plant Physiology Group, Research School of Biological Sciences, Building 46, The Australian National University, Canberra, ACT, 2601 Australia.
(Received December 31, 2007; Accepted February 18, 2008)
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