Pollination effects on patterns of ovule fate in Hesperis matronalis (Brassicaceae)

Abstract

We examined ovule positional effects on patterns of ovule development within linear fruits of the invasive weed, dame’s rocket, Hesperis matronalis L. Fruits were collected from two sites in southwestern Ontario, Canada. The majority of ovules within fruits were aborted early in development. Emergent patterns of ovule abortion and seed maturation within fruits were nonrandom and dependent on ovule position. The probability of seed maturation within individual fruits decreased significantly from basal to distal ends, suggesting an intrafruit resource gradient. Self-pollinated flowers at one site produced fruits with a similar pattern of seed maturation as was found for open-pollinated plants. However, cross-pollinated flowers produced fruits in which the pattern of seed maturation was reversed; more seeds were matured at the distal ends rather than the basal ends of fruits, indicative of a fertilization gradient. Analysis of pollen-tube growth showed that ovule failure may not be attributed to pollen limitation. For seeds produced via hand-pollinations, we found no relationship between seed mass and seedling biomass, although seeds from self-pollinations germinated more readily than did seeds from cross-pollinations. While patterns of ovule fate in H. matronalis can be manipulated by pollen source, the effects of such patterns on plant fitness are yet to be determined.