Partial and full dehydration impact on germination of 4 warm-season grasses

Precipitation patterns in the arid southwest U.S. can be highly variable during the summer monsoon season. The ability of germinating seeds to withstand temporary periods of dehydration may determine their potential for successful regeneration under present and future climatic regimes. Germination with short-term hydration and dehydration sequences was compared to constant water potential germination for sideoats grams [Bouteloua curtipendula (Michaux) Torrey], buffelgrass [Cenchrus ciliaris L.], Lehmann lovegrass [Eragrostis lehmanniana Nees], and kleingrass [Panicum coloratum L.]. Seeds were imbibed at -0.2 MPa for 1 to 4 days, then either air dried or partially dehydrated at -3.0 MPa for 1 to 4 days before being returned to the initial imbibition solution for a total 14-day incubation-dehydration period. One day of imbibition at -0.2 MPa advanced germination to a stage that resulted in significant reductions (P<0.05) in total germination from subsequent dehydration. The significant reductions still allowed >48% of the viable seeds to germinate after dehydration. Longer imbibition times also exhibited significant reductions in germination for buffelgrass and kleingrass. For kleingrass air-dried dehydration compared to -3.0 MPa produced significant reductions (P<0.05) in germination with 2-3 days imbibition. The length of the dehydration periods produced significant differences (P<0.05) in total germination for Lehmann lovegrass and kleingrass. Partial dehydration significantly increased germination rate for sideoats grama, buffelgrass, and kleingrass, white air-dried dehydration significantly reduced buffelgrass germination rate. Any dehydration during germination was detrimental and >1-day imbibition followed by dehydration seemed the critical time upon which a dramatic reduction in germination occurs.