Journal Article

Physiological Functions of the Water–Water Cycle (Mehler Reaction) and the Cyclic Electron Flow around PSI in Rice Leaves

Amane Makino, Chikahiro Miyake and Akiho Yokota

in Plant and Cell Physiology

Published on behalf of Japanese Society of Plant Physiologists

Volume 43, issue 9, pages 1017-1026
Published in print September 2002 | ISSN: 0032-0781
Published online September 2002 | e-ISSN: 1471-9053 | DOI: http://dx.doi.org/10.1093/pcp/pcf124
Physiological Functions of the Water–Water Cycle (Mehler Reaction) and the Cyclic Electron Flow around PSI in Rice Leaves

More Like This

Show all results sharing these subjects:

  • Biochemistry
  • Molecular and Cell Biology
  • Plant Sciences and Forestry

GO

Show Summary Details

Preview

Changes in chlorophyll fluorescence, P700+-absorbance and gas exchange during the induction phase and steady state of photosynthesis were simultaneously examined in rice (Oryza sativa L.), including the rbcS antisense plants. The quantum yield of photosystem II (ΦPSII) increased more rapidly than CO2 assimilation in 20% O2. This rapid increase in ΦPSII resulted from the electron flux through the water–water cycle (WWC) because of its dependency on O2. The electron flux of WWC reached a maximum just after illumination, and rapidly generated non-photochemical quenching (NPQ). With increasing CO2 assimilation, the electron flux of WWC and NPQ decreased. In 2% O2, WWC scarcely operated and ΦPSI was always higher than ΦPSII. This suggested that cyclic electron flow around PSI resulted in the formation of NPQ, which remained at higher levels in 2% O2. The electron flux of WWC in the rbcS antisense plants was lower, but these plants always showed a higher NPQ. This was also caused by the operation of the cyclic electron flow around PSI because of a higher ratio of ΦPSI/ΦPSII, irrespective of O2 concentration. The results indicate that WWC functions as a starter of photosynthesis by generating ΔpH across thylakoid membranes for NPQ formation, supplying ATP for carbon assimilation. However, WWC does not act to maintain a high NPQ, and ΦPSII is down-regulated by ΔpH generated via the cyclic electron flow around PSI.

Keywords: Keywords: Chlorophyll fluorescence — Cyclic electron flow (PSI) — Gas exchange (leaf) — Oryza sativa L. — Ribulose-1,5-bisophosphate carboxylase/oxygenase—Water–water cycle (Mehler reaction).; Abbreviations: IRGA, infrared gas analyzer; Ja, rate of alternative electron flow; Jf, rate of electron flow calculated from Chl fluorescence; Jg, rate of electron flow calculated from gas exchange; MDAR, monodehydroxylascorbate radical reductase; NPQ, non-photochemical quenching; PPFD, photosynthetic photon flux density; Rubisco, ribulose-1,5-bisphosphate carboxylase/oxygenase; ΔpH, pH gradient across the thylakoid membrane; ΦPSII, quantum yield of PSII photochemistry; P700, primary electron donor of PSI

Journal Article.  7745 words.  Illustrated.

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

Full text: subscription required

How to subscribe Recommend to my Librarian

Users without a subscription are not able to see the full content. Please, subscribe or login to access all content.