Modification of Pea Leaf Morphology by 2,3,5-Triiodobenzoic Acid

Single node explants of conventional, afila, and tendril-less peas (Pisum sativum L.) were cultured on a nutrient medium containing 2-200 μM TIBA. In conventional and tendril-less shoots, TIBA caused the development of: (i) a simple leaf rather than a compound leaf; (ii) a terminal leaflet in place of a normal tendril; (iii) a paripinnate leaf instead of the normal imparipinnate leaf; (iv) a ring fasciation; and (v) congenital fusion of two lateral leaflets. Tendrils borne on afila leaves were swollen radially and deeply cloven in the presence of TIBA. Pea leaf determination is a gradual process. Conventional pea tendrils are competent to form leaflet laminae, but they do not normally receive optimum levels of the appropriate signal at an early, critical stage. Afila tendril primordia are not competent to develop into leaflets. Tendrilless leaf primordia receive and can respond to signals for leaflet development. They are determined earlier than conventional leaves.