Root hairs are a primary site for nutrient absorption and for initiation of
signalling processes linked to variations of the root environment:plant-mi
crobe interactions or abiotic changes. In many of these cases, the earliest
detectable response is the modification of plasma membrane transports, det
ected through alteration of the electrical membrane potential. In spite of
this, root hairs have not been extensively used in electrophysiological res
earch so far. Problems with cell shape and current coupling are often prohi
bitive for microelectrode voltage-clamp on intact root hairs. In the presen
t study, these difficulties have been overcome and the ion channel currents
are described for young root hairs from alfalfa seedlings (Medicago sativa
cv Sitel). Electrophysiological and pharmacological studies indicated an i
nward rectifying K+ time-dependent current. This current was sensitive to t
etraethylammonium and Cs+ (10 mM each). Two other currents never shown in r
oot hairs were described: an outward rectifying time-dependent K+ current,
inhibited by tetraethylammonium and Cs+ (10 mM each) allowing K+ efflux und
er strong depolarizations and an instantaneous inward current identified as
an anion current, inhibited by 4-acetamido-4'-isothiocyanatostilbene-2,2'-
disulfonic acid and anthracene-9-carboxylic acid (100 mu M each). These res
ults should contribute to the understanding of root hair development and of
signalling processes in M. sativa root hairs. (C) 1999 Editions scientifiq
ues et medicales Elsevier SAS.