Phenotypic Plasticity for Reproductive Traits in Hermaphroditic Big Bluestem.

Big bluestem (Andropogon gerardii) was a dominant species over much of the natural Tallgrass Prairie. It has been widely used for forage, conservation, and habitat purposes throughout the Great Plains and is now being considered for bioenergy production on marginal land too dry for economic production of switchgrass biomass. The predominant sex expression in big bluestem is andromonoecy. However, variation exists among natural populations for frequency of plants with perfect pedicellate spikelets (hermaphrodites). Hermaphroditism has potential for increasing seed production, but little is known about the effect of environmental variation on the expression of the trait. This research evaluated eight hermaphroditic genotypes selected from ‘Sunnyview’ for two years at two locations for morphological components of seed production. Significant differences occurred between spikelet types (sessile vs. pedicellate) for seed set and seed size. Significant differences occurred among genotypes for inflorescence yield, spikelets inflorescence^-1, seed set, and seed size. Significant differences occurred between locations and between years for all traits. This research quantified the magnitude of phenotypic plasticity and level of genetic variation for phenotypic plasticity in this set of genotypes.