Pollen‒pistil interaction inLilium longiflorum: the role of the pistil in controlling pollen tube growth following cross- and self-pollinations

Abstract

By cytophysiological methods, the self-incompatibility mechanism of the breeding system inLilium longiflorumhas been examined with particular reference to the synthesis, location and nature of the stylar factors involved in the control of pollen tube development. A ‘bioassay’ has been developed by which the effect of stylar extracts on pollen tube elongation may be investigated. With use of this system, a crude fraction of proteins from the stylar fluid has been shown to inhibit pollen tube growth only when protein fractions from ‘self’ styles are used. The proteins of this fraction have been analysed by thin-layer gel electrofocusing. Changes in the profiles thus obtained following selfing and a heat treatment known to inactivate the self-incompatibility response indicate a highly polarized glycoprotein to be an active component of the system. The various ways by which such a glycoprotein could control pollen tube elongation are considered in detail, and these events inLiliumare discussed in the light of our knowledge of other self-incompatibility systems operating in angiosperms.