| Are diurnal patterns of stomatal movement the result of alternating metabolism of endogenous guard cell ABA and accumulation of ABA delivered to the apoplast around guard cells by transpiration? | |
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MedLine Citation:
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PMID: 15310824 Owner: NLM Status: MEDLINE |
Abstract/OtherAbstract:
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Abscisic acid (ABA) prevents opening of closed stomata and causes open stomata to close. A dual-source model is proposed linking ABA to diurnal stomatal movements. Darkness would favour guard cell biosynthesis of endogenous ABA and disfavour ABA catabolism. At first light, xanthophyll cycling, isomerization of ABA precursors, and activation of a cytochrome P450 mono-oxygenase (CytP450) would deplete endogenous guard cell ABA. The NADPH-requiring CytP450 would be activated by elevated O2 and reduced CO2 concentrations resulting from mesophyll photosynthesis. An increased O2-to-CO2 ratio would limit the Calvin cycle in guard cells, diverting NADPH produced by photosynthetic electron transport to the cytosol where, along with elevated O2, it would activate CytP450. Depletion of endogenous ABA would liberate guard cells to extrude protons and accumulate the ions and water needed to increase guard cell turgor and open stomata. By midday, stomata would be regulated by steady-state concentrations of ABA delivered to the apoplast around guard cells by transpiration. In temperate conditions, ABA would reach concentrations high enough to trigger ion efflux from guard cells, but too low to defeat the accumulation of sugars used to maintain opening. In dry conditions, ABA would reach effective concentrations by midday, high enough to trigger ion efflux and inhibit sugar uptake, reducing apertures for the rest of the day. At sunset, conditions would again favour biosynthesis and disfavour catabolism of endogenous guard cell ABA. The model can be used to reconcile proposed cellular mechanisms for guard cell signal transduction with patterns of stomatal movements in leaves. |
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Authors:
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Gary Tallman |
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Publication Detail:
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Type: Journal Article; Research Support, Non-U.S. Gov't; Research Support, U.S. Gov't, Non-P.H.S.; Review Date: 2004-08-13 |
Journal Detail:
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Title: Journal of experimental botany Volume: 55 ISSN: 0022-0957 ISO Abbreviation: J. Exp. Bot. Publication Date: 2004 Sep |
Date Detail:
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Created Date: 2004-08-24 Completed Date: 2004-12-09 Revised Date: 2008-11-21 |
Medline Journal Info:
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Nlm Unique ID: 9882906 Medline TA: J Exp Bot Country: England |
Other Details:
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Languages: eng Pagination: 1963-76 Citation Subset: IM |
Affiliation:
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Department of Biology, Willamette University, 900 State Street, Salem, OR 97301, USA. gtallman@willamette.edu |
Export Citation:
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APA/MLA Format Download EndNote Download BibTex |
| MeSH Terms | |
Descriptor/Qualifier:
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Abscisic Acid
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metabolism* Circadian Rhythm / physiology* Plant Physiological Phenomena* |
| Chemical | |
Reg. No./Substance:
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21293-29-8/Abscisic Acid |
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine
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