Relationship between pollen morphology and chromosome numbers in Brazilian species of Lippia L. (Verbenaceae)

Saulo M Sousa,Giovana A Torres,Lisete C Davide,Patrícia M.O Pierre,Lyderson F Viccini

doi:10.1590/s0001-37652013005000010

Abstract

The pollen morphology and exine structure of 17 species of Lippia L. were investigated in this work using light and scanning electron microscopy. Among the species studied, 14 showed tricolporate pollen grains, two had tri- and tetracolporate pollen grains and a single species exhibited, only tetracolporate pollen. The amb ranged from triangular to square, and the shape varied from oblate-spheroidal to prolate-spheroidal. Three different types of exine ornamentation were observed: psilate, scabrate and perforate. In addition to morphological data, we found positive association between the chromosome numbers and size of pollen grains, and also between the length and width of the colpi. The results indicate that the characteristics of pollen grains in Lippia may be used as an additional taxonomic character of the genus.

Highlights

Verbenaceae is a large-sized group of flowering plants included in the Asterids clade (Euasterids I), Lamiales (APG III 2009)
Only Raj (1983) used light micrscopy (LM), transmission electron microscopy (TEM) and scanning electron microscopy (SEM) data to compare 228 species belonging to 68 genera of Verbenaceae sensu lato
Pollen grains of the 17 taxa were examined under light microscope (LM) and scanning electron microscope (SEM)

Summary

Introduction

Verbenaceae is a large-sized group of flowering plants included in the Asterids clade (Euasterids I), Lamiales (APG III 2009). The first report about palynological data of 17 Lippia species indicate that pollen grains in Lippia are monads, mainly tri-colporate (some taxa have tetra-colporate grains), oblate-spheroidal to prolate-spheroidal, with polar axis varying from 17.45 to 40.32 μm and equatorial diameter from 17.27 to 40.21 μm (Table II, Figures 1 and 2). Variation on perforation density among taxa was observed such as L. corymbosa, L. hermanioides and L. rotundifolia that showed more perforations than other species with perforate exine, L. filifolia, L. lupulina, L. pohliana, L. pseudothea and L. rosella, (Figure 3 A-D).

Results

Conclusion