Staff Publications

Staff Publications

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    'Staff publications' is the digital repository of Wageningen University & Research

    'Staff publications' contains references to publications authored by Wageningen University staff from 1976 onward.

    Publications authored by the staff of the Research Institutes are available from 1995 onwards.

    Full text documents are added when available. The database is updated daily and currently holds about 240,000 items, of which 72,000 in open access.

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Record number 414723
Title Hydrogel Regulation of Xylem Water Flow: An Alternative Hypothesis
Author(s) Doorn, W.G. van; Hiemstra, T.; Fanourakis, D.
Source Plant Physiology 157 (2011)4. - ISSN 0032-0889 - p. 1642 - 1649.
DOI http://dx.doi.org/10.1104/pp.111.185314
Department(s) AFSG Quality in Chains
Chair Soil Chemistry and Chemical Soil Quality
Horticultural Supply Chains
PE&RC
Publication type Refereed Article in a scientific journal
Publication year 2011
Keyword(s) ion-mediated increase - induced vascular occlusions - intervessel pit membranes - hydraulic conductivity - bordered-pit - cell-walls - tracheary elements - angiosperm xylem - model films - cavitation
Abstract The concentration of cations in the xylem sap influences the rate of xylem water flow in angiosperm plants. It has been speculated that this is due to the shrinking and swelling of pectins in the pit membranes. However, there is as yet minimal evidence for the presence of pectin in pit membranes of angiosperms. The little pectin that has been found at the pit membrane edges of some species might not be adequate to explain the swelling and shrinking phenomena. The presence of hemicelluloses is also not certain. Lignin, by contrast, seems to be sometimes present, apart from cellulose, which is the main component. An alternative hypothesis is formulated, which involves the shrinking of any polyelectrolyte polymers in the pit membrane and a change in volume of the mobile phase in the pit pores. These phenomena are the result of electrostatic events. Some pit membrane polymers are negatively charged because of proton dissociation from functional groups. This charge is compensated by cations in the aqueous phase, which form a diffuse double layer (DDL). Inside the pit pores, an increase of the electrolyte concentration in the xylem sap will reduce the extent of the DDL. This will result in an increase in water flow. Additional flow enhancement, upon increase of the cation concentration, can be due to shrinkage of all membrane polymers. This contraction will also lead to an increase of the pit pore diameter. These processes will only be partly counteracted by forces that decrease the diameter of the pit pore due to relaxation.
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