Abstract
Plants perceive gradients in air moisture by their roots and elongate them toward water sources to effectively obtain a limited amount of water in soil (hydrotropism). A simple bioassay with an air-moisture gradient was developed to examine hydrotropic responses of roots in Arabidopsis thaliana seedlings. In this assay, hydrotropic responses of the mutants defective in AKT2 gene, which encodes a voltage-gated K+ channel, were slower than those of wild type. QRT-PCR showed that the expression of AKT2 in roots was increased by dehydration stress. Application of abscisic acid (ABA) to seedlings increased the AKT2 expression, whereas ABA inhibitors reduced it. Studies with ABA mutants also suggest that ABA participates in signaling response to hydrotropic stimulus. In addition, the expression of AKT2 gene in the elongation zone of roots was examined to clarify the role for AKT2 and ABA in hydrotropism.
