The Origin and Evolution of the Angiosperm Carpel

Abstract

The angiosperm carpel is one of the defining characteristics of flowering plants. Carpels are unique to angiosperms and are found in all of its members. Yet, due to the distinctive structure and function of carpels, deducing homologies among carpels and other seed-plant organs has been difficult. Progress in understanding carpel homologies and evolution is being made in a number of directions. Homologies, as well as transformations between them, have been proposed among angiosperms and other seed plants. These include homologies among the reproductive structures of Glossopterids, Caytonia, and other fossil taxa (e.g., Thomas, 1925, Thomas, 1957; Andrews, 1963; Stebbins, 1974; Doyle, 1978; Retallack and Dilcher, 1981a; Crane, 1985; Doyle and Donoghue, 1986b). Recent studies have examined the homologies and transformations among female reproductive organs through outgroup comparison (e.g., Crane, 1985; Doyle and Donoghue, 1986b; Taylor, 1991a) and interpretations of carpel structure within angiosperms (Taylor, 1991a). Developmental, morphogenic, and genetic studies have also provided additional insight on carpel structure and development (e.g., Szymkowiak and Sussex, 1992; Gasser and Robinson-Beers, 1993; Modrusan et al., 1994). Together, data from these diverse sources are leading to a revised view of carpel homology and structure.