Germination of Two Noxious Range Weeds Under Water and Salt Stresses with Variable Light Regimes1

Abstract

Russian knapweed and perennial pepperweed are invasive to meadow and riparian habitats in the semiarid intermountain west. Seed germination was tested to determine favored seedbed characteristics. Germination was inhibited in both species when water stress was imposed using polyethylene glycol. Knapweed achieved 60% germination after 40 d in dark and alternating light/dark environments. Pepperweed germination was greatest (30% after 14 d) in light and alternating light/ dark environments. Both species showed that germination declines when exposed to salt stress but continued to germinate under salt stress as high as 16 dSm−1. Nomenclature: Perennial pepperweed, Lepidium latifolium L. #3, LEPLA; Russian knapweed, Centaurea repens L. #3 CENRE. Additional index words: Riparian habitats, seedbed ecology.