Cell recognition in plants: Determinants of the stigma surface and their pollen interactions.

The interaction between compatible pollen grains and the female stigma of Gladiolus gandavensis has been used as a model system for investigation of cell recognition in plants. The molecular architecture of the receptive stigma surface has been investigated, and determinants binding to both concanavalin A and beta-glucosyl artificial carbohydrate antigen, as well as esterase activity, have been characterized, and conditions for their isolation have been established. The stigma surface, before and after modification, was found to bind (125)I-labeled proteins nonspecifically. Pollen tube penetration of the papillar cuticle is prevented when the receptor sites for concanavalin A are occupied. The concanavalin-A-binding determinants of the stigma surface have been fractionated to reveal several glycoproteins in the molecular weight range 43,000-93,000 and a group of glycolipids of molecular weight approximately 22,000. These results are interpreted in terms of two major recognition events regulating pollination.