Lack of S ‐allele interaction in monocot Tradescantia paludosa , evidenced by pollen behaviour

Previous seed‐set data having failed to reveal any S ‐allele interaction in Tradescantia paludosa , the behaviour of S ‐heterogenic pollen, with one or both of its S ‐alleles matched in the pistil, was studied by fluorescence microscopy to detect possible tendencies to partial dominance or competition that might be too weak to result in seed‐set but sufficiently strong to increase pollen tube growth. In neither case could such an increase be detected. It is concluded that lack of S ‐allele interaction is complete in the one‐locus self‐incompatibility system of T. paludosa , and that the presence of S ‐allele interaction forms a major line of demarcation between dicotyledonary and monocotyledonary angiosperms.