Pollen morphology of genus Allagopappus Cass. (Asteraceae: Inuleae), endemic to the Canary Islands, Spain

Abstract

The pollen of Canary endemic genus Allagopappus Cass., which includes two species, was examined by light and scanning electron microscopy. Ten populations in all were studied and the following parameters were measured: polar axis (P), equatorial diameter (E), polar exine thickness (Ex1), length (L) and thickness (A) of the spines in the meridional optical section, exine thickness at the centre of the mesocolpium in the interapertural area (Ex2) and distance between spines (De) in the equatorial optical section. The data were processed statistically by the Simpson & Roe graphical test, ANOVA I test for population analysis, and Student's t test for species analysis. Pollen grains are trizonocolporate with shape generally oblate–spheroidal and also prolate–spheroidal, spheroidal or suboblate. Tectum is complete, perforate, with supratectal spines. The results show that the pollen of the two species is very similar regarding shape, apertures, and ornamentation. Nevertheless, the Student's t test shows that pollen from Allagopappus viscosissimus Bolle is larger and it has a thicker exine than that of Allagopappus dichotomus (L. f.) Cass. with a highly significant difference. Furthermore, the ANOVA test seems to point out differences for P, E, Ex1, and Ex2 between populations.

Keywords:

• Allagopappus
• Canary Islands
• endemic genus
• light microscopy
• pollen
• scanning electron microscopy

Acknowledgements

We would like to express our gratitude to Dr. Manuel Nogales Hidalgo for his assistance in processing the statistical data with the software SPSS 14.0 and to Juan Luis González Álvarez, SEM operator of the University of La Laguna, for his collaboration in preparing the scanning electron micrographs.