POLLEN SIZE IN HORDEUM L - CORRELATION BETWEEN SIZE, PLOIDY LEVEL, AND BREEDING SYSTEM

The size of pollen in the genus Hordeum (Poaceae) is correlated with p loidy level and breeding system. Generally, the pollen size increases with the ploidy level, and outbreeding species possess significantly l arger pollen than inbreeders. In H. roshevitzii (2x), H. pusilplum (2x ), H. murinum subsp. murinum (4x), and H. parodii (6x) pollen, heterom orphisms occur between the central and the lateral florets of the trip let. In all four taxa, pollen from florets in which the anthers are ex serted is larger than pollen from florets where the anthers remain ins ide the floret. The biological consequences of heteromorphic pollen ar e discussed, and a model for the evolution of breeding strategies in H ordeum is suggested.