Ethylene, 2-Chloroethylphosphonic Acid, and Witchweed Germination

Abstract

In laboratory studies, ethylene and an ethylene-releasing agent, 2-chloroethylphosphonic acid (hereinafter referred to as CEPA), stimulated germination of aged, pretreated but still dormant witchweed ( Striga lutea Lour.) seed. Ethylene gas at 10 −1 μl/L produced maximal (89 to 98%) seed germination. Witchweed seed also germinated when incubated directly in Eustis loamy sand treated with CEPA. A half-maximal response was obtained with 10 mg of CEPA per kg of soil. Vapors produced by apple ( Pyrus malus L. Mill) slices, by an alkaline solution of CEPA, and by soil treated with CEPA also stimulated germination. Vapors from soil contained an inhibitor of the ethylene-induced seed germination. Exposure of the soil vapors to 20% potassium hydroxide removed the inhibitor. Germination studies with 10% carbon dioxide, carbon dioxide-free air, and ethylene indicated that carbon dioxide inhibited the ethylene-induced germination of witchweed seed.