Palynological study of the Venezuelan species of the genus Hymenocallis (Amaryllidaceae)

Abstract

Pollen morphology and exine structure of the seven Hymenocallis Salisb. species present in Venezuela were investigated using scanning (SEM) and transmission (TEM) electron microscopy. Pollen grains of all species are monosulcate, heteropolar, with bilateral symmetry, oblate to peroblate, heterobrochate, semitectate-columellate, possess unequal tectal surfaces, and are clavate or baculate when viewed with TEM. They present two equatorial apexes. When observed under SEM their surfaces appear as granulate; however, it is evident from TEM that they are in fact constituted by pila. All the species possess very large pollen (ranging from 64 to 85 lm and from 125 to 155 lm for polar and equatorial axes, respectively), and no relationship was evident between pollen size and chromosome number. All the taxa are also very similar in relation to their pollen outline, ornamentation and internal structure, thus indicating that the genus is accurately delimited from the palynological point of view and that discrete characteristics can only be used in some cases to delimit individual species.

Pollen morphology and its taxonomic significance in the genus Bomarea Mirb. (Alstroemeriaceae) - II. Subgenus Bomarea

“…Auriculate pollen grains are not common among extant plant taxa, and diverse Cretaceous pollen-bearing auriculate appendages have been variously described as gymnospermous and monocotyledonous (Elsik 1974). As the term "auriculae" is only applicable to the spores' structure (Punt et al 2007), the term "apex" has sometimes been used for these auriculalike pollen structures (see Martín et al 2012 for detailed terminological discussion).…”