title: Differential ovule development following self- and cross-pollination: the basis of self-sterility in Narcissus triandrus (Amaryllidaceae).
abstract: Self-pollination results in significantly lower seed set than cross-pollination in tristylous Narcissus triandrus. We investigated structural and functional aspects of pollen-pistil interactions and ovule-seed development following cross- and self-pollination to assess the timing and mechanism of self-sterility. Ovule development within an ovary was asynchronous at anthesis. There were no significant differences in pollen tube behavior following cross- vs. self-pollination during the first 6 d of growth, regardless of style morph type. Double fertilization was significantly higher following cross- vs. self-pollination. Aborted embryo development was not detected following either pollination type up to seed maturity. Prior to pollen tube entry, a significantly greater number of ovules ceased to develop following self- vs. cross-pollination. These results indicate that self-sterility in N. triandrus operates prezygotically but does not involve differential pollen tube growth typical of many self-incompatibility (SI) systems. Instead, low seed set following self-pollination is caused by a reduction in ovule availability resulting from embryo sac degeneration. We hypothesize that this is due to the absence of a required stimulus for normal ovule development. If this is correct, current concepts of SI may need to be broadened to include a wider range of pollen-pistil interactions.
authors.affiliation: Department of Botany, University of Toronto, 25 Willcocks Street, Toronto, Ontario, Canada M5S3B2.
authors.forename: T L
authors.initials: TL
authors.lastname: Sage
authors.forename: F
authors.initials: F
authors.lastname: Strumas
authors.forename: W W
authors.initials: WW
authors.lastname: Cole
authors.forename: S C
authors.initials: SC
authors.lastname: Barrett