Diversidade do óvulo e da semente em linhagens basais de Poales: uma perspectiva taxonômica e ecológica de seus representantes

Abstract

Poales is formed by 14 families, among them are Bromeliaceae, Rapateaceae and Typhaceae, which appear as basal lineages of the order. Several studies corroborate the basal position of these three families, however, there are still gaps to be filled regarding the circumscription of the taxa. Comparing already known data on ovule and seed development and structure can help elucidate some of these questions. In this context, the main objective of this work was to present data comparatively on structural characteristics of the ovary, ovules, seeds, and fruits of representatives of the basal lineages of Poales. For this, data from several bibliographic references were compiled, such as scientific papers, books, dissertations, and theses. The references found were also used to know the representativeness of the studied genus in each family quantitatively compare how much was studied among them. The results show that the three families have crassinucellate, anatropous, and bitegmic ovules, with the position of the ovary varying between superior and inferior. Concerning seeds, Bromeliaceae presents mostly anemochoric dispersion, however, in Bromelioideae the dispersion tends to be zoochoric through fleshy fruits and seeds with mucilaginous envelope. Rapateaceae has anemochoric dispersion over short distances and unknown means over long distances. Representatives of Typhaceae present two basic types of dispersion: anemochoric in Typha and hydrochoric in Sparganium. Rapateaceae and Bromeliaceae share characteristics, such as the presence of septal nectaries, partly corroborating their basal position. In addition, although the representatives of Typhaceae do not share characteristics other than those already described for the order, their basal position could be confirmed, along with the other two families, by the presence of basal characters such as hydrochory and the development of one seed per flower. Regarding the representative of the studies, the species of Bromeliaceae and Rapateaceae are being investigated more than those of Typhaceae. Studies on the diversity of ovules and seeds are important to understanding the phylogeny of these basal families, as well as in the conservation of Brazilian biodiversity, given the high number of endemic species found in our country.