Planta

, Volume 218, Issue 1, pp 107–114

Down-regulation of linear and activation of cyclic electron transport during drought

Original Article

DOI: 10.1007/s00425-003-1077-5

Cite this article as:
Golding, A.J. & Johnson, G.N. Planta (2003) 218: 107. doi:10.1007/s00425-003-1077-5

Abstract

The effects of short-term drought on the regulation of electron transport through photosystems I and II (PSI and PSII) have been studied in Hordeum vulgare L. cv. Chariot. Fluorescence measurements demonstrated that electron flow through PSII decreased in response to both drought and CO2 limitation. This was due to regulation, as opposed to photoinhibition. We demonstrate that this regulation occurs between the two photosystems—in contrast to PSII, PSI became more oxidised and the rate constant for P700 re-reduction decreased under these conditions. Thus, when carbon fixation is inhibited, electron transport is down-regulated to match the reduced requirement for electrons and minimise reactive oxygen production. At the same time non-photochemical quenching (NPQ) increases, alleviating the excitation pressure placed on PSII. We observe an increase in the proportion of PSI centres that are ‘active’ (i.e. can be oxidised with a saturating flash and then rapidly re-reduced) under the conditions when NPQ is increased. We suggest that these additional centres are primarily involved in cyclic electron transport, which generates the ΔpH to support NPQ and protect PSII.

Keywords

Cyclic electron transport Drought Hordeum (electron transport) Non-photochemical quenching ΔpH 

Abbreviations

A

assimilation rate

Ci

internal CO2 concentration

ETC

electron transport chain

g

stomatal conductance

FR

far red

k

pseudo first-order rate constant for the reduction of oxidised P700

NPQ

non-photochemical quenching

P700

primary electron donor of photosystem I

PSI, PSII

photosystem I, II

qP

proportion of open PSII centres

ROS

reactive oxygen species

ΔpH

pH gradient across the thylakoid membrane

ΦPSII

quantum yield of photosystem II

Copyright information

© Springer-Verlag 2003

Authors and Affiliations

  1. 1.School of Biological SciencesUniversity of ManchesterManchesterUK

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