Palynomorphological analysis of the genus Crocus L. (Iridaceae) in Iran and its taxonomic implications

Pollen from 20 populations representing 13 Iranian species of the genus Crocus was analyzed using light microscopy (LM) and scanning electron microscopy (SEM) to investigate the palyno-morphological features and their taxonomic significance. Polliniferous materials were sourced from either fresh plants or herbarium samples. For LM analysis, pollen grains were acetolyzed, while intact pollen grains were used for SEM micrographs. The study examined various pollen traits, including polar and equatorial diameters, aperture and meso-aperture width, exine thickness, and P/E ratios in LM analyses. Additionally, SEM observations focused on spinule width and length and the density of spinules and perforations on the exine. The investigation revealed that the pollen grains of Crocus are monads, oblate-spheroidal in shape, and measure approximately 61 to 106.48 micrometers along their equatorial axis. The smallest pollen grains were observed in C. reinhardii , while the largest were found in C. archibaldiorum . The pollen grains were intectate, with the exine irregularly perforated and covered with microechinate ornamentation. Two distinct types of pollen apertures were identified in the studied species: polyaperturoidate apertures in the two populations of Crocus haussknechtii from section Crocus and spiraaperturate pollen in the remaining taxa belonging to section Nudiscapus . Our data suggest that pollen characteristics offer valuable synapomorphies for delimiting sections within the genus Crocus , and also provide significant support for understanding and clarifying relationships within taxonomic aggregates and complexes.