Characteristics of seeds and seedlings from weeds treated with sublethal herbicide doses

Size, germination and viability of seeds as well as growth of seedlings derived from three weed species were studied in a pot trial. Fallopia convolvulus (L.) A. Loeve, Galium spurium L. and Thlaspi arvense L. were treated with MCPA or tribenuron-methyl at four doses and at five growth stages, from seedling stage to flowering. In G. spurium subnormal doses of tribenuronmethyl, applied at intermediate growth stages, greatly reduced seed weight, germination, viability, seedling shoot biomass and root biomass. Germination and viability, as well as the shoot biomass and root biomass of seedlings, were highly correlated with seed weight. In addition, but to a smaller extent, seed weight was reduced in F. convolvulus and T. arvense by tribenuron-methyl and in G. spurium by MCPA. Germination was reduced in F. convolvulus by MCPA and in T. arvense by tribenuron-methyl. However, the effects varied greatly depending on the growth stage at application.