Submitted to: Annals Of Botany
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: November 17, 1999
Publication Date: N/A
Interpretive Summary: Cheatgrass, an introduced annual weed, has infested millions of acres of rangeland in the western united states. One of the reasons that cheatgrass is so successful is that it can germinate and begin growth in the fall, winter and early spring when it is too cold for native perennial grasses to germinate. Previous laboratory research has shown that seed priming can induce native grass seeds to germinate faster at low temperatures. This study determined that primed native- grass seeds also germinate and emerge faster in the field. We studied germination in the laboratory under identical temperature conditions to seeds that were planted in our field plots. We used our data to construct models to predict how these seeds would germinate under historical conditions of soil temperature. We determined that maximum benefit could best be achieved during early spring planting when temperatures were near the base temperature for germination and sufficient water was available for seedling emergence.
Technical Abstract: Seed priming may enhance establishment success of cool- season range grasses which must compete with annual weeds for early spring moisture. Previous priming studies have confirmed germination rate enhancement for these species but relative treatment effects under field-temperature conditions have not been assessed. We primed seeds of thickspike wheatgrass [Elymus lanceolatus (Scribn. and J.G. Smith) Gould], bluebunch wheatgrass [Pseudoroegneria spicata (Pursh) L¿ve], Sandberg bluegrass (Poa sandbergii Vasey.) and bottlebrush squirreltail [Elymus elymoides (Raf.) Swezey] and evaluated their relative emergence rate in three soil types as a function of spring-planting date. Germination response was simultaneously evaluated in germinators that were programmed to simulate the field- temperature regime at planting depth. Seed priming enhanced both germination and emergence rate with the greatest effect occurring during the earlier, cooler planting dates. Total emergence and emergence rate in the field was lower than equivalent germination response in the laboratory. Thermal- germination response was modeled and predictions developed for evaluating potential germination under late winter/early spring soil-temperature regimes. Modeling results predicted that greater germination enhancement would have been possible at earlier planting dates than were measured in the field experiment.