Document Detail


Acclimation of leaves to low light produces large grana: the origin of the predominant attractive force at work.
MedLine Citation:
PMID:  23148276     Owner:  NLM     Status:  MEDLINE    
Abstract/OtherAbstract:
Photosynthetic membrane sacs (thylakoids) of plants form granal stacks interconnected by non-stacked thylakoids, thereby being able to fine-tune (i) photosynthesis, (ii) photoprotection and (iii) acclimation to the environment. Growth in low light leads to the formation of large grana, which sometimes contain as many as 160 thylakoids. The net surface charge of thylakoid membranes is negative, even in low-light-grown plants; so an attractive force is required to overcome the electrostatic repulsion. The theoretical van der Waals attraction is, however, at least 20-fold too small to play the role. We determined the enthalpy change, in the spontaneous stacking of previously unstacked thylakoids in the dark on addition of Mg(2+), to be zero or marginally positive (endothermic). The Gibbs free-energy change for the spontaneous process is necessarily negative, a requirement that can be met only by an increase in entropy for an endothermic process. We conclude that the dominant attractive force in thylakoid stacking is entropy-driven. Several mechanisms for increasing entropy upon stacking of thylakoid membranes in the dark, particularly in low-light plants, are discussed. In the light, which drives the chloroplast far away from equilibrium, granal stacking accelerates non-cyclic photophosphorylation, possibly enhancing the rate at which entropy is produced.
Authors:
Husen Jia; John R Liggins; Wah Soon Chow
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't    
Journal Detail:
Title:  Philosophical transactions of the Royal Society of London. Series B, Biological sciences     Volume:  367     ISSN:  1471-2970     ISO Abbreviation:  Philos. Trans. R. Soc. Lond., B, Biol. Sci.     Publication Date:  2012 Dec 
Date Detail:
Created Date:  2012-11-13     Completed Date:  2013-04-22     Revised Date:  2014-01-10    
Medline Journal Info:
Nlm Unique ID:  7503623     Medline TA:  Philos Trans R Soc Lond B Biol Sci     Country:  England    
Other Details:
Languages:  eng     Pagination:  3494-502     Citation Subset:  IM    
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MeSH Terms
Descriptor/Qualifier:
Acclimatization*
Adenosine Triphosphate / metabolism
Alocasia / drug effects,  metabolism,  radiation effects
Chloroplast Proton-Translocating ATPases / metabolism
Darkness
Energy Transfer
Entropy
Light*
Light-Harvesting Protein Complexes / metabolism
Magnesium / metabolism
Magnesium Chloride / pharmacology
Organelle Size / radiation effects*
Photophosphorylation
Photosynthesis
Plant Leaves / drug effects,  metabolism,  radiation effects*
Static Electricity
Thylakoids / drug effects,  metabolism,  radiation effects*
Chemical
Reg. No./Substance:
0/Light-Harvesting Protein Complexes; 02F3473H9O/Magnesium Chloride; 8L70Q75FXE/Adenosine Triphosphate; EC 3.6.3.-/Chloroplast Proton-Translocating ATPases; I38ZP9992A/Magnesium
Comments/Corrections

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