Desenvolvimento inicial, caracterização estrutural da flor, androsporogênese e androgametogênese em Dyckia racinae L.B.Sm.(Pitcairnioideae-Bromeliaceae)

Abstract

Important among monocots neotropical family, the bromeliads expand the richness and diversity of the ecosystems where occurs. So gather knowledge in pursuit for implementing projects really effective for biodiversity conservation becomes essential. Therefore, information on the structure of sporangia and gametophytes contribute to a better characterization of reproductive processes, and the application of the characters in taxonomic and phylogenetic analysis, whose results are of great value to conservation programs. This work seeks to understand embryology with emphasis on structural Dyckia racinae L.B.Sm., featuring aspects of early development of reproductive structures, androsporogenesis and androgametogenesis. The floral meristem of D. racinae in its developmental phase, possess a three layered structure: dermal, subdermal and central. In regions where the floral organs initiate development it is possible to identify a cytoplasmic condensation followed by a periclinal division in the subdermal layer. D. racinae shows perfect flowers, being such flowers trimerous, heterochlamydeous and subtended by a bract. The androecium consists of six stamens, and the ovary is superior, trilocular and nectaries are present and predominantly infralocular. The pattern formation of the anther parietal layers is basic type, the tapetum is secretory, the epidermis is papilate, and cytokinesis after meiosis is successive. After tetrads release from callose wall, the androspore maturation occurs, when is observed cytoplasm polarization, followed by first pollen mitosis that gives rise to generative and vegetative cells. In D. racinae the androphytes are shed in a two celled state, and sporoderme consist of an outer resistant exine and inner intine. Pollenkitt is observed at the pollen grain surface. Dimorphic pollen was observed. The dimorphic pollen present little volume and the aperture region remains concave, besides relatively less dense cytoplasm, delayed starch accumulation and delayed and partial regression of vacuole. In another grain type abnormal pollen mitosis was observed. In both type of grains vegetative and generative cells are not formed.