Morphological diversity and evolution of anther glands in Mimosoideae (Leguminosae).

Author(s)

Thais Cury de Barros

• Document type: Doctoral Thesis
• Press: Ribeirão Preto.
• Institution: Universidade de São Paulo (USP). Faculdade de Filosofia, Ciências e Letras de Ribeirão Preto (PCARP/BC)
• Defense date: 2016-05-06

Examining board members

Simone de Pádua Teixeira; Leonardo Maurici Borges; Silvia Rodrigues Machado; Ludmila Mickeliunas Pansarin; Joecildo Francisco Rocha

• Advisor: Simone de Pádua Teixeira

Abstract

In Mimosoideae (Leguminosae), anther glands are prominent structures because they occur in many taxa and provide characters with taxonomic value in the clade. The knowledge about the anther glands was mainly based on external morphological observations, lacking data concerning the anatomy, ontogeny, function and evolutionary aspects of the glands, which would contribute to a more detailed characterization and a more natural classification of these structures, as well as the inference of more objective ecological functions. The aims of this study were to revisit the structure of the anther glands, to investigate their meristematic origin, and their developmental stages, their functioning mechanisms, to infer ecological functions, and thus reconstruct the evolutionary history of these glands in Mimosoideae. For this, the present study investigated several aspects of the anther glands in 25 species of Mimosoideae representing groups with early and late divergences in the clade. We found four major types of glands in anther Mimosoideae: (1) Piptadenia type, characterized by a stalked gland with a spherical apex, and that includes three subtypes: Piptadenia, with the apex composed of isodiametrical cells; Adenanthera, with the apex composed a layer of elongated epidermal cells which delimits isodiametric cells; and Entada with the apex composed of a layer of epidermal bulky cells delimiting a lumen. (2) Pentaclethra type,a robust gland comprised of a layer of epidermal and palisade cells isodiametric central cells with vascularized peduncle. (3) The Prosopis africana type, a robust sessile and vascularized gland. (4) Finally, the Gagnebina type, an acuminate gland with elongated cells. Despite the morphological diversity, the anthers glands share a common meristematic origin. They arise from simultaneous divisions in the first three layers of meristematic cells covering the apical portion of the young anther, being classified as emergences. The types of glands may differ as to: (1) structure in the pre-anthesis and anthesis; (2) longevity; (3) aspect and chemical composition of exudate and (4) release form of exudate. Considering the characterization and release form of exudate, and behavior of floral visitors, our data show that the glands act mainly (a) in the production of substances that act on the accession of pollen to the bee body or anther and (b) in production of floral fragrance acting as osmophores. The presence of anther glands appears to have a single origin in Mimosoideae, with some loss events. The ancestral state of the structure of the glands probably corresponds to the type Piptadenia subtype Adenanthera. Still, there seems to be a negative relation between the presence of the glands, the presence of inflorescences with short axis, numerous stamens and united stamens. Our data indicate that in Mimosoideae, the glands in anthers provide characters with potential phylogenetic significance. The conserved meristematic origin of the anther glands beyond the single evolutionary origin of the presence of glands in anthers favor the hypothesis of homology of these structures and support the monophyly of Mimosoideae. (AU)

• FAPESP's process: 12/01296-8 - Morphological diversity and evolution of anther glands in Mimoseae (Mimosoideae, Leguminosae)
• Grantee: Thais Cury de Barros
• Support Opportunities: Scholarships in Brazil - Doctorate