Floral Development in the Capparales: Lepidium virginicum L. (Brassicaceae) and Tropaeolum majus L. (Tropaeloaceae). (Botany & Plant Ecology).

Floral Development in the Capparales: Lepidium virginicum L. (Brassicaceae) and Tropaeolum majus L. (Tropaeloaceae). Katherine Kantz and Christine M. Gwinn, Grand Valley State University, Biology Department, 1 Campus Drive, Allendale, MI 49401

We studied floral development in Lepidium virginicum (Poor-man's pepper) and Tropaeolum majus (Nasturtium) as part of a larger project to understand the evolution of floral form and development in the order Capparales. In L. virginicum, four sepal primordia arise in a helical pattern. Next four petal primordia arise unidirectionally from the abaxial to the adaxial side alternate with the sepals. Then two stamen primordia and the carpel primordium are initiated. In T. majus, five sepal primordia arise helically and then five petal primordia are initiated in a helical pattern alternate with the sepals. At the same time that the petals are being initiated, eight stamen primordia are initiated helically with five arising opposite the sepals and three arising opposite three of the petals. The position of the stamens relative to the sepals and petals is somewhat obscured later in development by expansion of the flower receptacle. The pattern of initiation of the eight stamens in T. majus suggests that they could ha ve been derived from a pattern often stamens in two whorls of five by suppression of two stamens in the inner whorl.