Dissertação
Ontogênese da antera, microsporogênese e microgametogênese de Dyckia strehliana H. Büneker & R. Pontes (bromeliaceae)
Fecha
2021-03-26Autor
Silva, Roberta Maidana da
Institución
Resumen
Many species of angiosperms are considered rheophytes, that is, they develop in the
banks of streams and fast-flowing rivers and are subject to the action of frequent floods,
as is the case of Dyckia strehliana H. Büneker & R. Pontes (Bromeliaceae). Also
considered saxicolous, its development occurs on basaltic rocky banks of the Toropi
River, in the municipality of Quevedos, RS. It is an endemic species in this region, an
area at risk of environmental degradation due to the construction of hydroelectric
plants, appearing as a threat to extinction. Thus, this study aimed to anatomically
analyze and describe the development of the anther of D. strehliana, in addition to
characterizing the embryological processes, microsporogenesis and
microgametogenesis, and the dynamics of starch during these stages. In order to carry
out the study, inflorescences were collected at different stages of development and
processed in the Structural Botany Laboratory. The emergence of stem primordia in
the floral meristem of D. strehliana occurs through layer II divisions. The formation of
the sporangium is of the basic type, the epidermis persists throughout development,
and its cells acquire a rounded shape during anther maturation. The endothelium
acquires U- and O-shaped thickening, the middle layer may divide again in some
places in the sporangium, degenerating into anther maturation. The mat is an invasive
secretor, starts a process of changing its chemical composition at the onset of meiosis
in archesporial cells and later has a tendency to invade the anther loculus. Meiosis is
successive, forming tetrads of isobilateral and decussed arrangement. Microspore
mitosis is asymmetric and pollen grains have a grooved opening. The sporoderm is
composed of lipid and protein exine, and pectic, protein and cellulosic intin. The
connective has fibrous thickenings. Raphids are common in the connective and
regions close to the locules. Pollen grains have a cycle of amylogenesis – amylolysis,
with a peak of starch accumulation during the phase in which the generative cell is
moved to the central position of the vegetative cell. Sporangium and connective
showed small amounts of starch grains during anther development, and in the mat they
were observed during degeneration. The general embryological results found are in
agreement with those described for Bromeliaceae and Dyckia, however, details related
to the tapetum and starch dynamics contrast D. strehliana from other species of the
genus. Such data are added to studies already carried out and contribute to future
studies. Thus, it will contribute to the characterization of the reproduction process,
phylogenetic relationships and will help for its conservation and preservation.