Geostimulation of root growth and pigment synthesis in mustard seedlings

Abstract

GRAVITY as an environmental factor affecting plant growth is generally considered to determine the direction of growth. However, an effect of gravity on the rate or intensity of growth—referred to in the older literature¹ as a geotonic, as distinct from a geotropic, effect—is also observable, as in, for example, the decreased growth rate of an inverted shoot. Geotonic effects have not received the attention given to tropic responses, possibly because of the experimental difficulty of clearly separating one from the other. Ideally, the tonic effect of gravity on growth activity should be demonstrable on some expression of growth unconnected with a geotropic correction. In the experiments reported here on the effect of gravity on the growth of mustard seedlings, we have observed a tonic effect of gravity on root growth and pigment synthesis.