Gravitropic response induced by coumarin : Evidences of ROS distribution involvement

Coumarin effects on gravitropic responses of Arabidopsis thaliana roots were here evaluated. Coumarin alone did not cause any alteration on gravitropic response showing a behavior similar to control plants. In contrast, TI BA and NPA, two auxin transport inhibitors, strongly modified root gravitropic responses. The addition of coumarin to the medium together with TI BA or NPA partially restored the effect of both inhibitors. Simultaneously, a semi-quantitative evaluation of ROS distribution was performed on root tips. TI BA and NPA caused a wide distribution of O2-, ROS oxidant species, around the root tip which disappeared with coumarin addition to both treatments, restoring ROS localized distribution. These results indicated a strong correlation between ROS distribution and coumarin-mediated recovery of root gravitropism.