Effect of the Striga Germination Stimulant on Extension Growth on the Roots of Peas

Abstract

THE seeds of Striga hermonthica, like those of certain closely allied parasites, will normally only germinate after they have been treated with a stimulant that is released from the roots of a large variety of species¹. The situation suggests that the parasite seed is supplied from actively growing host roots with a hormone which is normally required in germination but which is not synthesized by the seed². Moreover, the hormone only acts at a comparatively late stage in the germination process, and then it has the effect of promoting the extension of the cells of the radicle. When the radicle emerges, at first there is no division at the apex, and the increase in length is apparently due primarily to cell extension. Thus the hormone may be one that promotes cell extension in the root of Striga, and since it is produced from a large variety of species it may be one that stimulates extension growth in roots in general².