title: Calcium influx at the tip of growing root-hair cells of Arabidopsis thaliana.
abstract: The role of extracellular Ca(2+) in root-hair tip growth has been investigated in Arabidopsis thaliana (L.) Heynh. Root-hair length was found to be dependent on the concentration of Ca(2+) in the growth medium, with maximum length achieved at [Ca(2+)] of 0.3-3.0 mM. Using a non-intrusive calcium-specific vibrating microelectrode, an extracellular Ca(2+) gradient was detected at the tips of individual growing root-hair cells. The direction of the gradient indicated a net influx of Ca(2+) into root-hair cells. No gradient was detected near the sides of the root hairs or at the tips of non-growing root hairs. When root hairs were exposed to the Ca(2+)-channel blocker nifedipine, tip growth stopped and the extracellular Ca(2+) gradient was abolished. These results indicate that Ca(2+) influx through plasma-membrane Ca(2+) channels is required for normal root-hair tip growth.
authors.affiliation: Department of Biology, University of Michigan, 48109, Ann Arbor, MI, USA.
authors.forename: J W
authors.initials: JW
authors.lastname: Schiefelbein
authors.forename: A
authors.initials: A
authors.lastname: Shipley
authors.forename: P
authors.initials: P
authors.lastname: Rowse