Geotropic Behaviour of Roots

Abstract

Response of roots to a gravitational stimulus consisting of a sudden artificial change of orientation in the gravitational field can be resolved into a phase of very rapid curvature and reduced growth-rate which dies out rapidly and is followed by a phase of very slow response and normal growth-rate. A somewhat similar two-phased response to sudden reorientation is found in certain plagio- and diageotropic organs. The mechanism is discussed. Starch column chromatography has been used in an attempt to isolate growth factors which according to one postulate might be involved, and the significance of the findings is discussed. This technique is shown to be convenient for effecting volatile active substances which are lost in paper chromatography.