Occurrence of parietal and invasive tapetum in Dyckia strehliana (Bromeliaceae): first report for the Family

Abstract

Tapetal tissue plays essential roles in the formation of generative cells, as it is related to their nutrition and development in anthers. Among the few species of Bromeliaceae for which tapetal tissue has been describe, most have a secretory tapetum and one has an invasive tapetum. This study analyzed the developmental stages of the anthers of Dyckia strehliana, with emphasis on the tapetum, to identify variability in development and structure. Botanical material was collected on the banks of the Toropi River in the state of Rio Grande do Sul, Brazil, and processed using standard plant micro-techniques. During meiosis prophase, tapetal cells of some samples remained parietal while in the others, a proportional number, the invasion of the locular space begins, culminating in total invasion during the free microspore phase and without fusion of the protoplasts. Tapetal degeneration is complete before gametogenesis begins in both types. Thus, it is possible to describe two modes of development and tapetal structure, one parietal and one invasive, although the tapetum remains as a general secretory type in both cases. Thus, according to present work, the terms invasive and parietal are indicators of states of the secretory tapetum.