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Ion transport and metal sensitivity of vacuolar channels from the roots of the aquatic plant Eichhornia crassipes
Author(s) -
Paganetto A.,
Carpaneto A.,
Gambale F.
Publication year - 2001
Publication title -
plant, cell and environment
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.646
H-Index - 200
eISSN - 1365-3040
pISSN - 0140-7791
DOI - 10.1046/j.1365-3040.2001.00777.x
Subject(s) - eichhornia crassipes , chemistry , ion transporter , botany , biophysics , aquatic plant , biology , biochemistry , membrane , ecology , macrophyte
Using the patch‐clamp technique, we investigated the transport properties of vacuolar ion channels from the roots of water hyacinth, Eichhornia crassipes (Mart. Solms, Pontederiacae). Eichhornia crassipes vacuoles displayed large voltage‐dependent rectifying slow‐vacuolar (SV) currents, which activated in a few seconds at positive potentials and deactivated at negative voltages in a few hundreds of millseconds. Similarly to SV channel previously identified in the tonoplast of terrestrial plants, SV currents in E. crassipes were activated by micromolar concentrations of Ca 2+ and current slightly increased (25%) on addition (10 m m ) of the reducing agent dithiothreitol (DTT). Eichhornia crassipes SV channels were equally permeable to K + and Na + . The permeability sequence derived from current values is: K + ≈ Na + > Rb + > NH 4 + ≈ Cs + >> TEA + . Excised membrane patches displayed single channel transitions typical of SV‐type single channel openings with a conductance of (83·0 ± 5·6) pS; a smaller channel with a conductance of (31·0 ± 2·7) pS was also identified. Metals such as Ni 2+ and Zn 2+ decreased the vacuolar current in a reversible manner. However, although Zn 2+ inhibition is comparable to that induced by the same metal in vacuoles from the main root of sugar beet ( Beta vulgaris L.), the inhibition of the SV currents by Ni 2+ is not as substantial in E. crassipes as in sugar beet. To our knowledge, this is the first electrophysiological characterization of ionic transport in E. crassipes , a pervasive troublesome aquatic weed, which has exceptional absorption properties of several water contaminants such as heavy metals, pesticides and phenols.