Pollen morphology and exine ultrastructure of Brasiliocroton P.E. Berry &amp; Cordeiro (Euphorbiaceae)

Lidian Ribeiro De Souza,Daniela Santos Carneiro-Torres,Francisco De Assis Ribeiro Dos Santos

doi:10.1590/0102-33062019abb0183

Pollen morphology and exine ultrastructure of Brasiliocroton P.E. Berry & Cordeiro (Euphorbiaceae)

Lidian Ribeiro De Souza, Daniela Santos Carneiro-Torres + Show 1 more

Open Access

https://doi.org/10.1590/0102-33062019abb0183

Copy DOI

Abstract

ABSTRACT The present study aimed to morphologically characterize the pollen grains of species of Brasiliocroton mamoninha and B. muricatus in order to expand palynological knowledge of the group and provide additional micromorphological information useful for studies of the relationships within Crotoneae. Polleniferous material was acetolysed and described using light, scanning electron and transmission microscopy. The pollen grains of the two species of Brasiliocroton were apolar, spherical, inaperaturate and medium-sized with a Croton ornamentation pattern. The Croton pattern of B. mamoninha is formed by subtriangular pila, >5-plicate with pointed apices, while for B. muricatus it is formed by subcircular to circular pila, <5-plicate with rounded apices. Ultrastructural analysis revealed a stratified sexine in both species, whereas variation in the pattern of deposition of the foot layer allowed the species to be palynologically distinguished from each other. The composition of the Croton pattern of ornamentation, the morphology of the ultrastructure of the wall and the range of variation in the diameter of the pollen grains differed between the studied species, and thus are diagnostic characters. Pollen morphology allowed the two species of Brasiliocroton to be palynologically separated, and provided data that will be useful for taxonomically circumscribing these taxa.

Highlights

Brasiliocroton was described by Berry et al (2005a) based on morphological and molecular data
The Croton pattern of B. mamoninha is formed by subtriangular pila, >5-plicate with pointed apices, while for B. muricatus it is formed by subcircular to circular pila,
The pollen studied could be differentiated between the two species. Characteristics, such as variation in the size of the pollen grains associated with differences in the composition of the exine ornamentation of the Croton pattern and morphology of the wall ultrastructure (Fig. 2), allowed the species to be palynologically separated

Summary

Introduction

Brasiliocroton was described by Berry et al (2005a) based on morphological and molecular data. Despite its close proximity to Croton, Brasiliocroton was initially identified as belonging to Micrandra, probably due to the similar leaf blades and inflorescence form, distal position of the female flowers and disposition of the fruits on the lateral branches of the panicle (Berry et al 2005a). Brasiliocroton belongs to tribe Crotoneae (Berry et al 2005b) in subfamily Crotonoideae (Wurdack et al 2005). Tribe Crotoneae comprises six genera (Webster 2014), of which Brasiliocroton is this most recently described (Berry et al 2005a). The genus is sister to Croton, which is the main clade of the tribe (Berry et al 2005b) and the second largest and most diverse genus of Euphorbiaceae (Webster 1993; Berry et al 2005b)

Objectives

Methods

Results

Discussion

Conclusion