Induction of secondary dormancy in Amaranthus caudatus seeds

Nondormant A. caudatus seeds germinated in the dark at temperatures between 20 and 35degrees but not at 45 degreesC. Incubation at this temperature for at least 10 h inhibited seed germination over the temperature range 20 to 35 degreesC, temperatures previously suitable for germination. Thus incubation at 45 degreesC induced secondary dormancy. Mechanical or chemical scarification or exposure to pure oxygen caused complete or almost complete germination of dormant seeds although more slowly in comparison to nondormant seeds. Secondary dormant scarified seeds required a lower concentration of ABA than nondormant seeds to inhibit germination. The high temperature, which induced dormancy, 45 degreesC, caused the seed coat to be partially responsible for secondary dormancy. Involvement of ABA (synthesis or sensitivity) in the induction and/or maintenance of this dormancy should be considered.