Floral structure of Guarea macrophylla Vahl and Trichilia claussenii C.DC. (Meliaceae): functional aspects and implications in the systematics and evolution of Sapindales

• Autor(a) principal: Gama, Rebeca Laino
• Data de Publicação: 2018
• Tipo de documento: Dissertação
• Idioma: eng
• Título da fonte: Biblioteca Digital de Teses e Dissertações da USP
• Texto Completo: http://www.teses.usp.br/teses/disponiveis/41/41132/tde-20092018-103856/
• topic: Anatomia; Anatomy; Desenvolvimento; Development; Dimorfismo sexual; Meliaceae; Meliaceae; Sexual dimosphism; Sistemática; Systematic

The reproductive systems of angiosperms are quite diverse. In the flowers of Meliaceae (Sapindales) we found a wide diversity of these systems, including reports of monoecious, dioecious and polygamous plants. However, the sexual dimorphism of flowers in the family is very subtle, and structurally each flower always has a gynoecium and a developed androecium, even though functionally one or the other may be sterile (pistillodes or staminodes). Consequently, the determination of floral sexuality in the family is often difficult or even inconclusive in many taxa, and the available data often come from the analysis of herbarium material. This lack of detailed information on floral structure, development and function still prevent an accurate identification of floral sexuality in most members of Meliaceae, and also limits a comparison with the data known to other representatives of Sapindales, especially in relation to the structure and development of the carpels and stamens in the families most closely related, which are Rutaceae and Simaroubaceae. Studies on flower development associated with pollination studies and phylogenetic through comparative analysis, provide a better understanding on how these systems behave, and allow a more accurate classification of the sexual system present in particular species, leading to evolutionary data and assisting in clarifying kinship issues. The present dissertation addresses a detailed study of the structure of flowers of two Brazilian taxa (Trichilia claussenii and Guarea macrophylla subsp. tuberculate) belonging to the subfamily Melioideae, with emphasis on the organization and development of their sexual systems. Our study includes analysis of the external morphology, anatomy, vascularization, ontogeny, and histochemical tests of both species. We also analyzed the functional aspects of flowers of T. claussenii, related to floral sexuality, which was evaluated by means of pollination tests, associated to tests of pollen viability, stigmatic receptivity and morphoanatomic and ontogenetic analyzes. Among the main results, floral dimorphism was detected only in T. claussenii, which is likely gynodioecius, and provided with a peculiar sterility of the androecium in the female flower morphotype: pollen grains remain concealed by a secretion from the tapetum. In addition, we promote the discussion of pathways of the evolution of sexual systems within the Meliaceae, as well as of its main flower and fruit morphological characters, through hypotheses evaluated upon the current molecular phylogenetic framework of the family