Seed Dormancy Characteristics of Sideoats Gramagrass, Bouteloua curtipendula (Michx.) Torr.1

Abstract

Seed sources of sideoats gramagrass [Bouteloua curtipendula (Michx.) Torr.] were accumulated from central and western United States, Mexico, and Argentina to evaluate duration and pattern of seed dormancy and to locate and identify dormancy conditioning factors of intact seed units (spikes of multiple spikelets). Dormant and nondormant seed sources were chosen for detailed investigations. Effects of time, removal of floral parts (glumes, lemmas, paleas, and awns), soil, leaching treatments, enriched oxygen atmosphere on germination, and potential inhibitors of seed units on germination of seed were studied. Postharvest dormancy was present in seed units of all sources, but disappeared after 4 to 6 months of dry storage after harvest. Postharvest dormancy was conditioned by nature of the caryopses. Long‐term dormancy persisted in seed units for 5 years in dormant sources without viability change. Long‐term dormancy was broken when floral parts were removed from caryopses. Placing seed units in soil, in enriched oxygen atmosphere, and in sodium hypochlorite was effective in breaking dormancy. The mechanism of longterm dormancy of sideoats gramagrass seed units involved interactions among the following factors: light weight of caryopses, impermeable floral parts of caryopses, and presence of coumarin‐like inhibitory compounds. Association of dormancy with establishment under stress environments of grasslands is to be determined. Results of this investigation offer approaches to select and characterize germplasm with dormancy qualities that may be favorable to establishment.