Factors contributing to the regulation of thermoinhibition in Tagetes minuta L

Thermoinhibition in Tagetes minuta achenes is tightly and rapidly regulated with regard to its imposition and release, with both processes occurring within 2-3h. Germination at high temperatures is almost exclusively regulated by the embryo, while the pericarp appears to play only a minor role. Thermoinhibition in T. minuta could not be alleviated by any single plant growth regulator application, but a combination of treatments that both reduced ABA levels and increased ethylene levels were able to restore germination at supraoptimal temperatures. This suggests a role for both ethylene and ABA in the imposition of thermoinhibition in this species.