The role of the root cap in the response of the primary roots of Zea mays L. seedlings to white light and to gravity.

Investigations into the relationship between the light-induced inhibition of root elongation and the response of Zea mays primary roots to gravity have revealed a close similarity between growth-inhibiting factor(s) produced in response to both stimuli. Evidence is presented that the inhibiting factor(s) produced in the root cap on exposure to white light can be used by the root to produce curvature in response to gravitational stimulation in darkness, i.e. under conditions in which dark exposed roots do not normally respond to gravity.The implications of these findings on the way in which roots respond to geotropic stimulation are discussed.