NaC1 uptake in roots of Zea mays seedlings: comparison of root pressure probe and EDX data

The extent by which salinity affects plant growth depends partly on the ability of the plant to exclude NaCl. To study the uptake of NaCl into excised roots of Zea mays L. cv. 'Tanker', two different techniques were applied. A root pressure probe was used to record steady state as well as...

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Bibliographic Details
Published inAnnals of botany Vol. 70; no. 6; pp. 543 - 550
Main Authors Frensch, J, Stelzer, R, Steudle, E
Format Journal Article
LanguageEnglish
Published 1992
Subjects
chemical analysis
growth
ion transport
osmotic pressure
potassium chloride
root hydraulic conductivity
roots
salinity
seedlings
sodium chloride
stress response
X-radiation
x-ray microanalysis
Zea mays
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Summary:The extent by which salinity affects plant growth depends partly on the ability of the plant to exclude NaCl. To study the uptake of NaCl into excised roots of Zea mays L. cv. 'Tanker', two different techniques were applied. A root pressure probe was used to record steady state as well as transient values of root (xylem) pressure upon exposure of the root to media containing NaCl and KCl as osmotic solutes. In treatments with NaCl, pressure/time responses of the root indicated a significant uptake of NaCl into the xylem. NaCl induced kinetics were completely reversible when the NaCl solution was replaced by an isosmotic KCl solution. This indicated a passive movement of Na+-salts across the root cylinder. Root samples were taken at different times of exposure to NaCl and prepared for X-ray microanalysis (EDX analysis). Radial profiles of ion concentrations (Na+, K-, Cl-) were measured in cell vacuoles and xylem vessels along the root axis. Na+ appeared rapidly in mature xylem (early metaxylem) and living xylem (late metaxylem) before it was detectable in vacuoles of the root cortex. EDX results confirmed that the kinetics observed by the pressure probe technique corresponded mainly to an influx of Na+-salts into early metaxylem. In late metaxylem, the uptake of Na+ was associated with a decline of K-. The Na+/K+ exchange indicated a mechanism to reduce sodium from the transpiration stream.
ISSN:0305-7364
1095-8290