The systematic value of pollen morphology of Passiflora subgenus Astrophea (Passifloraceae)

Abstract

This study investigates and reports the pollen morphology of a selected group of Passiflora species of the subgenus Astrophea. We found that species can be grouped into five pollen types, four of which had been previously documented. The fifth new pollen type was observed in P. macrophylla. This pollen type completely lacks muri, and possesses spines and bacula on a granulate surface. All of the species of the subgenus Astrophea studied have the same type of aperture: 6-colporate with 3 lalongate endoapertures, one for each pair of ectoapertures. Multivariate analyses performed with quantitative characters showed a great degree of similarity between type I, II and V pollen, and individual distinction of type III and type IV. The pollen characters observed do not support the currently accepted taxonomic classification for the Passiflora subgenus Astrophea, but are useful for delimiting species.

Taxonomy, palynology and distribution notes of seven species of Passiflora L. (Passifloraceae s.s.) newly recorded from Brazil

“…This was also confirmed for P. subg. Astrophea by Mezzonato-Pires et al (2017), who found that amongst all pollen characters, the most significant was the sexine ornamentation.…”

“…It is morphologically most similar to P. fuchsiiflora , being differentiated from the latter by its flowers with yellow to orange-yellow corona and dolabriform-triangular outer corona filaments. Both species possess pollen grains of the IV type (Mezzonato-Pires et al 2017) due to their reticulate sexine and small lumina.…”

“…It possesses widely ovate and chartaceous leaf-blades, with round to slightly emarginate apex, added to the three filament series of the corona, with subdolabriform outer filaments and the two inner series with tuberculate filaments. The pollen grains possess reticulate sexine with small lumina and, for this reason, the pollen was included by Mezzonato-Pires et al (2017) in the type IV pollen group.…”

“…The pollen grains of the closely related P. cerradensis Sacco present semitectate exine and reticulate sexine with large and ornamented lumina; which differ greatly from the mostly non-tectate exine, not producing lumina, pollen grains of P. jussieui . The pollen grains of P. jussieui are included in the type II pollen group, while the ones of P. cerradensis are included in the type III pollen group (Mezzonato-Pires et al 2017). …”

“…For sectional classification of the species, the authors followed Radford et al (1974) and Feuillet and MacDougal (2003). For the description of structures, the terminology used by Punt et al (2007) and Mezzonato-Pires et al (2017) was also used. Field photographs were only available for P. amoena .…”