Evaluation the effects of different factors on the seed germination and dormancy-breaking of Knapweed (Centaurea balsamita Lam.)

Knapweed (Centaurea balsamita Lam.) is an annual winter weed in Asteraceae. It is expanding in winter cereal fields of Iran. During 2015, an experiment was conducted in the Weed Science Laboratory, Department of Agronomy & Plant breeding in the College of Agriculture and Natural Resources, University of Tehran. Different levels of osmotic potential, salinity, PH, KNO3, GA3 and burial depths at 20 ̊C were evaluated. Results showed that C. balsamita has a good tolerance to drought stress (-0.76 MPa), but it is sensitive to soil salinity. The best pH is neutral for germination. C. balsamita seeds reacted to KNO3 and GA3 treatment well. By increasing KNO3 and GA3, germination percentage raised. This weed grows in shallow depths (3 cm). Most germination occurs at the soil surface. Deep plowing is, therefore, recommended to prevent seed germination.