Dependence on Light of Geotropism in Plant Roots

Abstract

PLANTS grown in non-porous containers frequently show a lower concentration of roots on the periphery of the block of soil than similar plants grown in porous containers¹, and there is sometimes a tendency for the direction of growth of these peripheral roots to be more nearly vertical in non-porous than in porous containers^2,3. Gradients of water, nutrient or gas concentration, or of soil temperature, have been suggested as causes of these phenomena, but there is also the possibility that light has an effect, since many non-porous containers made of glass or plastics are transparent, whereas porous ‘clay’ pots are opaque.