Notes on the size and exine ornamentation of Avena pollen grains

Abstract

Pollen grain size and exine ornamentation were examined in 13 species of Avena L. (Poaceae), including six A-genome diploids, four tetraploids, and three hexaploids. A cultivated species was represented at each ploidy level. It was found that both pollen size and exine sculpturing patterns showed some correlation with the cytogenetic, morphological, and biochemical evidence which has been used in elucidating the taxonomic relationships within both the A-genome diploids and the hexaploids. However, the pollen data shed less light on relationships within the tetraploids and on relationships between the different ploidy levels. It was observed that the cultivated species at each ploidy level tended to have larger pollen grains and a more complex mode of exine process patterning than their wild relatives. Possible explanations were discussed.