|Author: ||A.V. Etcheverry|
|Keywords: ||Crotalaria stipularia, delayed selfing, floral morphology, Papilionoideae, pollination, secondary pollen presentation|
The flowers of Crotalaria stipularia Desv. are protandrous, last for five days, and have two whorls of stamens with differential growth and dimorphic anthers.
The long anthers of antisepalous (outer) stamens dehisce during the 24 h before anthesis, while the round anthers of antipetalous (inner) stamens do so 24 h after flower opening (Day 1). The filaments of antipetalous stamens grow linearly from 1 mm in the bud to ca. 5 mm 48 h after opening (Day 2), forcing the mass of pollen progressively into the tip of the keel.
The stigma is terminal, relatively small and membraneless.
It is surrounded by a whorl of non-receptive hairs, which, while turgid (Day1-2), inhibit contact between the flower’s pollen mass and stigma.
The long anthers produce 86% of the total pollen.
Nectar is secreted from the receptacle around the base of the ovary, and accumulates within the staminal furrow, which has a basal opening to allow visitor´s access. Epanthidium erythrocephalum and Pseudocentron sp. (Megachilidae) trigger the pollination mechanism (brush type). The P/O ratio suggests this species is facultatively xenogamous.
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