Characteristics and Movement of the Flowering Stimulus from the Induced Leaf of Xanthium

Abstract

A technique of photo-inducing single-leaved cocklebur plants (Xanthium saccharatum) for the production of floral primordia, followed by removal of the leaf after various time intervals and under different dark and light conditions provided a method for studying the time required for formation and translocation of the flowering stimulus from its site of synthesis, the leaf, and the effect of light on its movement and lability. It was found that the substance moves out of the leaf shortly after it is formed under optimal conditions and a minimal period of about 24 hrs. is adequate for formation and translocation of sufficient amounts of the floral stimulus to induce the formation of floral primordia at the apical meristem. Light does not destroy this substance while still in the leaf, and light following the dark period specifically hastens its movement out of the leaf to the terminal meristem.