Pollen dimorphism in Silene alba (Caryophyllaceae)

Abstract

Male plants of S. alba are found to possess 1 of 2 pollen types, distinguished by the ektexine structure. In 1 type, found in 58% of the plants examined, the ektexine is punctate with spinulose and tubuliferous elements, whereas the other type has a reticulate-spinulose ektexine. Associated with the ektexine features are differences in grain diameter, wall thickness, and pore number. In the related species S. noctiflora and S. dioica, all of the pollen examined had a reticulate-spinulose ektexine. No evidence could be found for the possibility that the reticulate ektexine in S. alba might be due to introgression from S. dioica. Pollen dimorphism was not hitherto reported in the Caryophyllales (Centrospermae), now was it previously established in a dioecious species. This appears also to be the 1st report of genetically controlled pollen dimorphism in a species that does not exhibit heterostyly.