Control gates and micro-ecology: The pollen-stigma interaction in perspective

The pollen and stigma are well adapted to generate micro-environments for pollen germination, tube growth, fertilization and the avoidance of subvention of the pollination pathway by invading pathogens. The sequence of events as the female tissues of stigma, style and ovary mature and prepare for pollination and fertilization is outlined in terms of 'gates' opening. Following maturation and passage of the pollen tube or gamete nuclei, a series of equivalent gates close, some serving a prophylactic role (particularly in the Gramineae), others related to incompatibility reactions or conservation of water. The roles of the micro-ecology of the stigma and style, and of the gates. are discussed in the light of the success of angiosperms as a group, and analogies are made with the success of the mammals in the animal kingdom. Taken together, the paper presents a review, in part, of Jack Heslop-Harrison's work on the pollen-stigma interaction in the held of reproductive physiology. (C) 2000 Annals of Botany Company.