Abstract
Roots display positive hydrotropism in response to a moisture gradient, which regulates the directional growth by interactions with other tropisms such as gravitropism. To dissect the molecular mechanism underlying hydrotropism in seedling roots, we established a method for screening Arabidopsis mutants defective in root hydrotropism, and we have successfully obtained 12 mutants of which root hydrotropism is reduced to various extents. Among them, roots of a mutant named rhy1 (root hydrotropism 1) were found to be unique because they showed ahydrotropic response although their growth rate was normal, and they normally displayed gravitropism, phototropism and waving response. Roots of other rhy mutants (rhy2, rhy3, rhy4) showed the reduced hydrotropism together with either a reduced gravitropism or a reduced waving response. Currently, we are attempting to clarify factor(s) responsible for hydrotropism by identifying the mutated genes in the rhy
mutants.
