Use of Ethylene and Nitrate to Break Seed Dormancy of Common Lambsquarters (Chenopodium album)

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Abstract
Effects of ethylene and KNO3 on the germination of dormant common lambsquarters (Chenopodium album L. # CHEAL) seed were studied under controlled environmental conditions. Ethylene, applied in the gaseous form or as an aqueous solution of ethephon (2-chloroethylphosphonic acid), was able to overcome the dormancy of over 70% of the seed. The optimum concentrations of ethylene and ethephon were 10 μL·L-1 and 100 mg·L-1, respectively. The dormancy-breaking action of ethylene was dependent on the availability of nitrate. Hence, seed containing a high level of endogenous nitrate responded readily to ethylene, whereas nitrate-deficient seed required a combined application of ethylene and nitrate. Stimulation of seed germination by ethylene was observed in soil at all depths studied (up to 15 cm). The sensitivity of seed to ethylene increased upon imbibition to reach a peak on the third day, followed by a steady decline. Consequently, the greatest promotion of germination occurred when ethylene was administered during the first 3 to 4 days of imbibition. The loss of seed sensitivity was neither preempted nor overcome by an exogenous supply of KNO3, and may imply that the seed had passed into secondary dormancy. The present findings could form the basis for the use of ethylene to accomplish commercially significant promotion of germination in the field and thus improve the efficiency of the control of common lambsquarters.