Origin and variation of polymerous gynoecia in Fabaceae: evidence from floral mutants of pea (Pisum sativum L.)

Polymerous gynoecia are normally found in some members of Fabaceae, although the vast majority of this family is characterized by a gynoecium consisting of a single carpel. Summarizing the variation of gynoecium features in these species together with analysis of floral structure and ontogeny in mutants of pea (Pisum sativum L.) suggests to propose two different ways of gynoecium polymerization in legumes. The first is homeotic replacement of the stamens into carpels observed in stp mutants of pea and possibly causing the multicarpellate habit in mimosoids. The second deals with flower fusion within an inflorescence, a transformation observed in fasciated forms of pea together with the mutants coch and det. Similar processes might contribute to formation of the bicarpellate flowers of some swartzioid legumes. The polymerous gynoecium evolved in Fabaceae at least twice independently.