Document Detail

Co-regulation of dark and light reactions in three biochemical subtypes of C(4) species.
MedLine Citation:
PMID:  20549356     Owner:  NLM     Status:  MEDLINE    
Regulation of light harvesting in response to changes in light intensity, CO(2) and O(2) concentration was studied in C(4) species representing three different metabolic subtypes: Sorghum bicolor (NADP-malic enzyme), Amaranthus edulis (NAD-malic enzyme), and Panicum texanum (PEP-carboxykinase). Several photosynthetic parameters were measured on the intact leaf level including CO(2) assimilation rates, O(2) evolution, photosystem II activities, thylakoid proton circuit and dissipation of excitation energy. Gross rates of O(2) evolution (J(O)₂'), measured by analysis of chlorophyll fluorescence), net rates of O(2) evolution and CO(2) assimilation responded in parallel to changes in light and CO(2) levels. The C(4) subtypes had similar energy requirements for photosynthesis since there were no significant differences in maximal quantum efficiencies for gross rates of O(2) evolution (average value = 0.072 O(2)/quanta absorbed, approximately 14 quanta per O(2) evolved). At saturating actinic light intensities, when photosynthesis was suppressed by decreasing CO(2), ATP synthase proton conductivity (g (H) (+)) responded strongly to changes in electron flow, decreasing linearly with J(O)₂', which was previously observed in C(3) plants. It is proposed that g (H) (+) is controlled at the substrate level by inorganic phosphate availability. The results suggest development of nonphotochemical quenching in C(4) plants is controlled by a decrease in g (H) (+), which causes an increase in proton motive force by restricting proton efflux from the lumen, rather than by cyclic or pseudocyclic electron flow.
Olavi Kiirats; David M Kramer; Gerald E Edwards
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Publication Detail:
Type:  Journal Article; Research Support, U.S. Gov't, Non-P.H.S.     Date:  2010-06-12
Journal Detail:
Title:  Photosynthesis research     Volume:  105     ISSN:  1573-5079     ISO Abbreviation:  Photosyn. Res.     Publication Date:  2010 Aug 
Date Detail:
Created Date:  2010-08-13     Completed Date:  2011-03-17     Revised Date:  2011-06-24    
Medline Journal Info:
Nlm Unique ID:  100954728     Medline TA:  Photosynth Res     Country:  Netherlands    
Other Details:
Languages:  eng     Pagination:  89-99     Citation Subset:  IM    
School of Biological Sciences, Washington State University, Pullman, WA 99164-4236, USA.
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MeSH Terms
Amaranthus / metabolism*,  radiation effects
Carbon / metabolism*
Carbon Dioxide / metabolism
Oxygen / metabolism
Panicum / metabolism*,  radiation effects
Photosynthesis / physiology,  radiation effects
Photosystem II Protein Complex / metabolism
Plant Leaves / metabolism,  radiation effects
Sorghum / metabolism*,  radiation effects
Species Specificity
Reg. No./Substance:
0/Photosystem II Protein Complex; 124-38-9/Carbon Dioxide; 7440-44-0/Carbon; 7782-44-7/Oxygen

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