Water Stress-Induced Germination of Giant Foxtail (Setaria faberi) Seeds

Abstract

Giant foxtail (Setaria faberi Herrm. # SETFA) seed germination was about 55% in water but increased to >90% after pretreatment in polyethyleneglycol 8000 (PEG) at water potentials of −0.3 MPa or less. Pretreatment at 20 C required about 24 h exposure to PEG for maximum effect, but at 35 C shorter times (4 to 8 h) gave a partial effect. Treatment with PEG can begin at the time of seed wetting or after the seeds have imbibed water for 24 h. Continuous exposure to a water potential of −0.5 MPa PEG (or less) imhibited germination. Other methods of applying temporary water stress to the seeds, such as slow hydration in a humid atmosphere, or drying after partial hydration, increased germination in a manner similar to PEG treatment. The relatively slow response kinetics with PEG suggest that increased germination was caused by physiological adaptation to water stress, possibly by observed adjustments in seed water potential. It is suggested the water stress mechanism could operate under field conditions where wetting-drying cycles are common.