Pollen Size and Pollen Viability in Big Bluestem as Related to Spikelet Type

Abstract

The utilization of big bluestem, Andropogon gerardii Vitman, for revegetation is limited by seed availability. Although several factors influence seed production in cross‐pollinated species, effective pollination is essential for seed set. Objectives of this study were to compare pollen grain size and viability from pedicellate and sessile spikelets of six big bluestem accessions in each of 2 yr. Coulter Counter measurements of mean pollen diameter varied significantly with spikelet type and year. The mode pollen diameter varied with accession, spikelet type, and year. Mean and mode pollen diameters were consistently larger in sessile than pedicellate spikelets. Differences in pollen viability were attributable to accession, spikelet type, and an accession by spikelet interaction. Among accessions, pedicellate‐spikelet pollen viability varied from 4 to 78% averaged over years, and in two accessions was nearly as high as the sessile spikelet. Phenotypic variation in pedicellate‐spikelet pollen viability suggests that selection for this trait should be effective, assuming heritable variation of sufficient magnitude.