Taxonomic significance of palynomorphological characteristics of selected Centranthus (Caprifoliaceae) species

Abstract

Pollen morphology of herbarium specimens of four Centranthus species (C. ruber, C. longiflorus, C. kellereri and C. calcitrapae) was studied using LM and SEM. The research aim was to provide data on their pollen characteristics and to evaluate the taxonomic value of these data for species-specific identification. Pollen grains are tricolpate, suboblate to prolate (P/E = 0.81-1.42); medium- or large-sized (P = 49.21-90.44 μm; E = 43.89-93.10 μm). Colpi are long or medium-length, wide at equator, tapered to acute or obtuse ends. Exine sculpture is echinatemicroechinate-nanoechinate; echini (1.00-1.39 μm high) and microechini (0.55-0.98 μm) are conical, with straight or convex sides and acute apices, nanoechini are 0.22-0.46 μm high. Most important characters of taxa diagnostic at species level for the taxonomy are: size of pollen and colpi, exine structure, size of echini and microechini, and pattern of tectum in areas between echini. Pollen grains of C. calcitrapae and C. macrosiphon (sect. Calcitrapa) are generally smaller in size than grains of C. ruber, C. longiflorus and C. kellereri (sect. Centranthus). Pollen of C. kellereri was analysed for the first time in the current study.