MORFOLOGIA E ESTRUTURA DA ESPORODERME DOS GRÃOS DE PÓLEN DE ESPÉCIES SUL-AMERICANAS DE PASSIFLORA L. (PASSIFLORACEAE)

Abstract

The Palynology is an excellent method for several areas in Biology. Passifloraceae is very interesting, since it shows a great variability of pollen characteristics, mostly very unsuficciently explored. In Brazil, few studies use palynology and the study of the sporoderm structure in pollen grain, which could fills existing gaps. The studied genus, Passiflora, has four subgenres, from which Passiflora, Astrophea and Decaloba were studied in this work. Their pollen variations were deeply studied, with the objective of describing the morphological and histochemical structure of the sporoderm of Passiflora occurring in South America, trying to supply additional tools for the family's phylogeny. We inferred evolutive trends, and also described number of apertures, type, reticle and variations in morphology, in addition to variations of the sporoderm and we related them with possible evolutive tendencies for the group. The analyzed samples came from collections on Rio Grande do Sul, Paraná, Espírito Santo, Pará and Colombia. Eighteen species of the genus were analyzed, with 13 from de subgenre Passiflora, 3 Decaloba and 2 Astrophea. The buttons before anthesis were stored in FAA fixative 50% and histochemical tests were performed following the Johansen (1940) protocol and acetolysis. Boxplot analysis were performed to represent the variation of size in the pollen grains through R x64 Software version 3.3.0 and for cluster analysis the program Mesquite 3.40 (build 877) was used. The work was developed in the Laboratório de Botânica Estrutural from Universidde Estadual do Centro-Oeste. As a result, the grains didn't fall far from the patterns from literarute, with some exceptions. The species of the subgenre Passiflora have fused colpo, varying from 6 to 12, with reticulated exine of type 2. The species from the subgenre Astrophea presented colpores and the species of Decaloba varied in the type of apertures. For the histochemistry of the sporoderm, the subgenre Passiflora showed thick intine, thin endexine and abscence of the basal layer, among other characteristics that varied according to species or level of subgenre. The size of the pollen grain seemed to be related to the thickness of the intine, and consequently related to possible pollinators. Through the cluster analysis, we stress the affinity of species with its subgenres. As a conclusion, the joined analysis of the ultrastructure of the sporoderm and the external morphology were useful for an almost complete interpretation of the variations that ocurr in the genus, giving us information that the subgenre Passiflora is derivative in relation to the other two. Besides, the present work has raised some hypothesis that may contribute to future phylogenetic analysis inside the group.