Stamen dimorphism in Rhododendron ferrugineum (Ericaceae): development and function.

The function of stamen dimorphism in the breeding system of the alpine shrub Rhododendron ferrugineum was studied in two populations in the French Alps. This species has pentameric flowers with two whorls of stamens: an inner whorl of five long stamens and an outer whorl of short stamens. We studied the development of stamens from buds to mature flowers (measurement of the filament, anther, and style lengths at five successive phenological stages) and compared the size and position of reproductive organs at maturity in control and partially emasculated flowers (removal of long-level stamens) to determine whether the presence of long-level stamens constitutes a constraint for the development of the short-level ones.