Abstract
Plants are sessile in nature, and need to detect and respond to many environmental cues in order to establish their stand. Plants can sense environmental signals and display tropisms, and it is widely accepted that auxin plays an important role in these responses. Recent analyses using Arabidopsis have emphasized the importance of polar auxin transport and differential auxin responses to gravitropism. Nonetheless, the involvement of auxin in hydrotropism remains unclear. To clarify whether or not auxin is involved in the hydrotropism, we treated Arabidopsis seedlings with inhibitors of auxin influx, efflux, and response, and examined their effects on both hydrotropic and gravitropic responses. In agreement with previous reports, gravitropism was inhibited by all the chemicals tested. In contrast, only an inhibitor of the auxin response significantly reduced hydrotropism. These results suggest that auxin response, apart from its polar transport, plays definite role in hydrotropic response.
