Floral vascular anatomy of Piriqueta racemosa, Turnera hassleriana and Turnera joelii (Turneraceae)

Abstract

The floral vascular anatomy of three species be10nging to two genera of Turneraceae is analyzed. The indumentum and the anatomical structure of peduncle, prophylls, perianth, nectaries, crown, androeciurn and gynoecium are described as well. The ovary is surrounded by a tube, the appendicular nature of which is confirmed: its basal portion is composed of calyx, corolla and staminal filaments, and its distal portion is formed only by the perianth. The expression "floral tube" is used to name this structure, following Takhtajan (1991). The nectaries are placed between the perianth and the stamens; in Piriqueta they are adnated to the floral tube while in Turnera they are located on the stamens. T. joelii seems to be more advanced because of the development of a nectar pocket. The crown is present only in Piriqueta, it has papillose epidermal cells and no vascular supply. Each episepalous stamen is supplied by one amphicribal bundle, which ends in the connective tissue. The wall of the mature anther is composed of epidermis and endothecium. Pollen grains are tricolporate and reticulate. The gynoecium has transmission tissue on the apical inner surface of the ovary (compitum), covering the placentae, ascending within the styles and appearing on the stigmas. The ovules are anatropous, bitegmic, crassinucelate, with zigzag micropyle.