Effects of several chemicals and burial of seeds into the soil on dormancy-breaking of weed species.
Dormant seeds of 52 weed species were treated with chemicals, including KNO3, KOH, thiourea, H2O2 and gibberellin (GA3). The germination percentages of Setaria glauca [S. pumila], Ambrosia trifida and Ranunculus sceleratus were increased by KNO3. S. pumila and R. sceleratus germination percentages were also increased by thiourea. Germination of S. viridis and S. pumila was promoted by H2O2. S. viridis, S. pumila and Cyperus sanguinolentus germination percentages were increased by pectinase [polygalacturonase] treatment. Gibberellin treatment enhanced the germination of Eleusine indica and R. sceleratus, and had slight effects on other species. E. indica germination percentage had a linear relationship with gibberellin concentration. The dormancy of seeds buried in soil for longer than 1 month during winter was drastically decreased, and germination was increased under alternating temperatures (25 and 15°C). The germination rates of Chenopodium ficifolium and C. album were increased by approximately 50% under alternating temperatures after burial for 7 weeks.