The Role of Brassinosteroids in Shoot Gravitropism 1(C)(W)

In the current model of gravitropism, negative gravitropic (upward) growth of the shoot of a dicotyledonous plant involves sedimentation of starchcontaining plastids (statoliths) in the endodermis (starch sheath). Here, we show that high levels of brassinosteroids (BRs) counteract gravitropic growth, while BR deficiency enhances gravitropism irrespective of the presence of a functional starch sheath. These data support a role for BRs as negative regulators of