Relationship Between Inflorescence Size and Seed Production in Barnyardgrass (Echinochloa crus-galli)

Abstract

Barnyardgrass inflorescence length ranged from less than 2 to over 20 cm. Inflorescences less than 4 cm long were a single first-order raceme, while the largest had 20 to 50 primary branch racemes. Inflorescences longer than about 12 cm and with more than about 12 racemes showed second-order branching. Air-dried structural biomass increased from less than 2 milligrams for the smallest to over 300 milligrams for the largest inflorescences. Inflorescence length and structural biomass were positively correlated (r2= 0.95). Floret numbers increased from about 15 for smallest inflorescences to over 2000 for largest inflorescences and were positively correlated with inflorescence length (r2= 0.94) and with inflorescence structural biomass (r2= 0.94). Biomass of caryopses plus aborted florets had the same relationships as those for floret number. Measurement of frequency distribution of size and determination of numbers of inflorescences per plant should provide a means to predict fecundity in barnyardgrass.