Journal Article

Changes in the Thermal Dissipation and the Electron Flow in the Water–Water Cycle in Rice Grown Under Conditions of Physiologically Low Temperature

Naoki Hirotsu, Amane Makino, Ayuko Ushio and Tadahiko Mae

in Plant and Cell Physiology

Published on behalf of Japanese Society of Plant Physiologists

Volume 45, issue 5, pages 635-644
Published in print May 2004 | ISSN: 0032-0781
Published online May 2004 | e-ISSN: 1471-9053 | DOI: http://dx.doi.org/10.1093/pcp/pch075
Changes in the Thermal Dissipation and the Electron Flow in the Water–Water Cycle in Rice Grown Under Conditions of Physiologically Low Temperature

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  • Biochemistry
  • Molecular and Cell Biology
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Effects of low temperature on chlorophyll (Chl) fluorescence, gas exchange rate, the amounts of xanthophyll cycle pigments (Xp) and the activities of several antioxidant enzymes were examined in the 8th leaf of two rice (Oryza sativa L.) cultivars (japonica and indica types) and rbcS antisense rice. All plants were grown hydroponically at 25/20°C (day/night), and then exposed to 20/17°C (day/night) after full expansion of the 8th leaf, or exposed to either 20/17°C or 15/13°C (day/night) during the expansion of the 8th leaf. All plants exposed to low temperatures showed a decrease in CO2 assimilation rate without photoinhibition, and increases in the fraction of thermal dissipation in PSII, and in the electron flux through the water–water cycle (WWC) were observed. Although the increase of thermal dissipation was associated with increases in the ratio of carotenoids to Chl, the ratio of Xp to carotenoids and the de-epoxidation state of Xp, the increase of the electron flux of WWC was not accompanied by an increase in the activities of antioxidant enzymes. Such photoprotective responses did not differ between during and after full expansion of the leaf, and did not differ among the three genotypes. Quantitative analyses on the dissipation of excess light energy showed that thermal dissipation makes a larger contribution than WWC. Thus, although low temperature led to a decrease in CO2 assimilation, rice potentially coped with the excess light energy by increasing the thermal dissipation and the electron flux of WWC under low temperature irrespective of leaf development and genotypes.

Keywords: Keywords: Chlorophyll fluorescence — Gas exchange (leaf) — Low temperature — Oryza sativa L. — Water–water cycle — Xanthophyll cycle pigments.; Abbreviations: A, antheraxanthin; APX, ascorbate peroxidase; Ja, rate of alternative electron flow; Jf, rate of electron flow calculated from Chl fluorescence; GR, glutathione reductase; Jg, rate of electron flow calculated from gas exchange, NPQ, non-photochemical quenching; PPFD, photosynthetic photon flux density; Rubisco, ribulose-1,5-bisphosphate carboxylase/oxygenase; SOD, superoxide dismutase; V, violaxanthin; Z, zeaxanthin; ΔpH, pH gradient across the thylakoid membrane.

Journal Article.  5691 words.  Illustrated.

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

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