Floral development of urticalean rosids

Abstract

This proposal aims to compare the morphology of the developing flower in the clade of urticalean rosids, which comprises Ulmaceae, Cannabaceae, Urticaceae and Moraceae. This group share characteristics mostly from the flower, considered to be reduced in relation to other angiosperms: small, inconspicuous, diclinous (= unisexual), with missing perianth or one-whorled perianth, one-whorled androecium with number of stamens equal to or less than the perianth organs, bicarpelar gynoecium, pseudomonomerous, or sometimes transformed into pistiloid in staminate flower or aborted in pistillate flower, only one functional ovule which is attached to the ovary by different manners, and several stigma forms. Data from floral development will elucidate some interesting and yet puzzling questions for the group: (1) Is there an ontogenetic pattern that results in the reduced flower? (2) What are the pathways (absence from the beginning or abortion) that promote the diclinous (= unisexual), with missing or one-whorled perianth flower? Are these pathways similar in species with different sexual expressions (monoecy, ginodioecy, dioecy, androdioecy, polygamy)? (3) Variations in the merism of the perianth, the androecium and the gynoecium result of primordium absence, subdivision or abortion? (4) The perianth formed by single whorl is composed of sepals or petals? (5) The ascidiate carpel, previously reported in some genera of Moraceae, but considered the basal condition in angiosperms, can be confirmed in the studied species? Seventeen species of 17 genera of four families will be studied. Flower buds of various sizes and flowers will be collected from at least two individuals per species and processed for surface (scanning electron microscopy) and histological (light microscopy) analyses. The main products expected for this proposal are to train researchers devoted to developmental studies and elucidation of important morphological issues in reproduction of plants, as well as to fill gaps in the knowledge of plant development biology, a little explored area in Brazil. (AU)