Document Detail

Proton and copper adsorption to maize and soybean root cell walls.
MedLine Citation:
PMID:  16666628     Owner:  NLM     Status:  PubMed-not-MEDLINE    
A surface complexation model which has been used to describe inner-sphere complexation on metal oxide surfaces was applied to the adsorption of Cu by isolated cell walls of 4-day and 28-day-old maize (Zea mays L. cv WF9 x Mo17) and 21-day-old soybean (Glycine max [L.] Merr. cv Dare) roots. Concentration dependence of the titration data prevented the determination of unique pK and capacitance values for the 4-day maize cell walls, though mean values obtained for the intrinsic pK of the titratable carboxyl groups were 3.0 (4-day maize), 3.6 (28-day maize), and 3.0 (21-day soybean) as determined by potentiometric titration with either NaOH or HCl in 20 millimolar NaCl. The constant capacitance model was applied to Cu sorption data from rapid batch equilibrium experiments in an ionic medium of 20 millimolar NaClO(4). Speciation calculations indicated that the formation of a bidentate surface complex was sufficient to describe the experimental data for all three types of plant material, with only one value for the pK and capacitance density. The intrinsic constants of Cu complexation by a neutral site are: log K = -0.3 +/- 0.1, -0.2 +/- 0.3, and 0.9 +/- 0.1 for 4-day and 28-day maize, and 21-day soybean, respectively. The integral capacitance density parameter, which describes the relationship between surface charge density and electrical potential, is several times larger than for crystalline mineral surfaces. This result indicates that the surface electrical potential remains low even when the surface charge density is high. Such behavior is characteristic of gels and porous oxides.
D L Allan; W M Jarrell
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Publication Detail:
Type:  Journal Article    
Journal Detail:
Title:  Plant physiology     Volume:  89     ISSN:  0032-0889     ISO Abbreviation:  Plant Physiol.     Publication Date:  1989 Mar 
Date Detail:
Created Date:  2010-06-29     Completed Date:  2010-07-06     Revised Date:  2010-09-15    
Medline Journal Info:
Nlm Unique ID:  0401224     Medline TA:  Plant Physiol     Country:  United States    
Other Details:
Languages:  eng     Pagination:  823-32     Citation Subset:  -    
Department of Soil and Environmental Sciences, University of California, Riverside, California 95251.
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