Journal Article

The Photosynthetic Properties of Rice Leaves Treated with Low Temperature and High Irradiance

Naoki Hirotsu, Amane Makino, Satoshi Yokota and Tadahiko Mae

in Plant and Cell Physiology

Published on behalf of Japanese Society of Plant Physiologists

Volume 46, issue 8, pages 1377-1383
Published in print August 2005 | ISSN: 0032-0781
Published online August 2005 | e-ISSN: 1471-9053 | DOI: http://dx.doi.org/10.1093/pcp/pci149
The Photosynthetic Properties of Rice Leaves Treated with Low Temperature and High Irradiance

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  • Plant Sciences and Forestry

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Photosynthetic characteristics in rice (Oryza sativa L.) leaves were examined after treatment with low temperature (15°C) and high irradiance (1,500 µmol quanta m–2 s–1). Decreases in quantum efficiencies in PSII (ΦPSII) and PSI (ΦPSI) and in the rate of CO2 assimilation were observed with a decrease in the maximal quantum efficiency of PSII (Fv/Fm) by simultaneous measurements of Chl fluorescence, P700+ absorbance and gas exchange. The decreases in ΦPSII were most highly correlated with those in CO2 assimilation. Although the initial (the activity immediately measured upon extraction) and total (the activity following pre-incubation with CO2 and Mg2+) activities of ribulose-1,5-bisphosphate (RuBP) carboxylase/oxygenase (Rubisco) decreased slightly, the maximal activity (the activity following treatment with SO4 2–) of Rubisco remained almost constant. These results indicate that the decrease in CO2 assimilation rate with the decreasing Fv/Fm was not caused by a decrease in Rubisco activity but rather by a decrease in RuBP regeneration capacity which resulted from the decrease in the rate of the linear electron transport. On the other hand, the decrease in ΦPSI was very small and the ratio of ΦPSI to ΦPSII increased. The de-epoxidation state of xanthophyll cycle pigments also increased. Thus, the cyclic electron transport around PSI occurred in photoinhibited leaves.

Keywords: Cyclic electron flow around PSI; Gas exchange (leaf); Low temperature; Oryza sativa L.; Photoinhibition; Ribulose-1,5-bisphosphate carboxylase/oxygenase; A, antheraxanthin; ΔAmax, ΔAsat, ΔAact, maximal, variable and steady-state absorbance change of P700+; FBPase, fructose-1,6-bisphosphatase; Fv/Fm, the maximal quantum efficiency of PSII; Fv′/Fm′, the efficiency of excitation energy capture by open PSII; JPSI, the electron transport rate at PSI; k, rate constant for reduction of P700+; P700, primary electron donor of PSI; pCi, the intercellular partial pressure of CO2; ΔpH, pH gradient across the thylakoid membrane; ΦPSI, the quantum efficiency of PSI; ΦPSII, the quantum efficiency of PSII; RuBP, ribulose-1,5-bisphosphate; SBPase, sedoheptulose-1,7-bisphosphatase; V, violaxanthin; Z, zeaxanthin

Journal Article.  5006 words.  Illustrated.

Subjects: Biochemistry ; Molecular and Cell Biology ; Plant Sciences and Forestry

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