The effects of physical damage on seed production in flowering plants of Saponaria officinalis

Abstract

Individual flowering ramets in a large riverbank stand of Saponaria officinalis, bouncingbet, were subjected to three damage treatments at anthesis: removal of most flowers, removal of all leaves, and bending of the stem just below the inflorescence. All seeds were collected from ripened capsules of treated plants as well as from a group shaded by a canopy of Convolvulus sepium and from an untreated control group. Seeds from the defloration treatment were significantly heavier than those from the other treatments. In the control, bent stem, and shaded treatments the seed masses were distributed in a bimodal manner, with most seeds forming a normal distribution around a midpoint of 1.5–1.7 mg and a cohort of heavy seeds having a mean mass of 2.5 mg. This heavy cohort (mode) was missing from the defoliation treatment. Of the total variation in seed mass, 36% was among individuals, 54% was among inflorescences within individuals, and only 10% was within inflorescences. This suggests that resources are allocated differentially between capsules at different positions on the inflorescence but almost uniformly within the individual capsule. Key words: defoliation, defloration, bouncingbet, seed production, Saponaria officinalis.