Down-regulation of linear and activation of cyclic electron transport during drought |
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Authors: | Alison?J?Golding Email author" target="_blank">Giles?N?JohnsonEmail author |
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Institution: | (1) School of Biological Sciences, University of Manchester, 3.164 Stopford Building, Oxford Road, Manchester, M13 9PT, UK |
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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 pH to support NPQ and protect PSII.Abbreviations
A
assimilation rate
- Ci
internal CO2 concentration
- ETC
electron transport chain
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g
stomatal conductance
- FR
far red
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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
- pH
pH gradient across the thylakoid membrane
- PSII
quantum yield of photosystem II
An erratum to this article can be found at |
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Keywords: | Cyclic electron transport Drought Hordeum (electron transport) Non-photochemical quenching pH" target="_blank">gif" alt="Delta" align="BASELINE" BORDER="0">pH |
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