Role of calcium and other ions in directing root hair tip growth

The study investigated the role of Ca2+, K+, and H+ ions in the growth of Limnobium stoloniferum root hairs using ion-selective microelectrodes. It was found that Ca2+ and H+ influxes were localized to the tips of growing root hairs, indicating their potential role in directing growth, while K+ influx was uniform along the root hair. The presence of Ca2+ was crucial for root hair integrity, although its influx magnitude did not determine growth rate. Aluminum was identified as a potent inhibitor of root hair growth, completely blocking Ca2+ influx at higher concentrations and causing growth inhibition and tip swelling at lower concentrations. This suggested that aluminum might affect multiple sites within the cell, potentially contributing to its toxicity.