Cytoplasmic Free Calcium Distributions During the Development of Root Hairs of Arabidopsis Thaliana

This study investigated the role of cytoplasmic free calcium concentration ([Ca2+]c) in the development of root hairs in Arabidopsis thaliana. It was found that while [Ca2+]c did not predict the initiation site of root hairs, once initiated, emerging root hairs exhibited elevated [Ca2+]c in their apical cytoplasm. During a 3–5 hour phase of sustained elongation, rapidly elongating root hairs showed a highly localized elevated [Ca2+]c at the tip, which was absent in non-growing hairs. The rhd-2 mutant, defective in sustained growth, displayed altered [Ca2+]c distribution. The study suggested that Ca2+ channel activity at the root hair tip is crucial for maintaining growth, as evidenced by the effects of verapamil and manganese treatments. Overall, the data indicated that while Ca2+ does not initiate root hair growth, it is essential for sustaining elongation through Ca2+ influx at the tip.