Three trials were carried out to study the effects of different methods to overcome dormancy, light quality and sowing depth on the germination and emergence of Xanthium strumarim L. (cocklebur). In the first trial, under growth chamber conditions, the treatments consisted of 5 methods of seed scarification: mechanical (sand-paper). Chemical (concentrated sulphuric acid for 10 min), sowing treatment (2 hours soaking in water), physical (thermal shock: 2 min in water at 80oC) and the control, which resulted in germination percentages of 100%, 93%, 93%, 87% and 80%, respectively, without significant differences between the treatments; the sowing treatment caused lower germination speed (IVG). In the second trial, under identical conditions, the light quality treatment consisted of 6 light filters, resulting in the following germination percentages: blue - 450 nm (13%), gree - 500 nm (33%), red - 700 nm (13%), distant red - 760 nm (7%), darkness (26%) and transparency - without absortion at 380 to 760 nm (control, 73%), indicating that this species can be considered a preferencial photoblastic. In the third trial, under greenhouse conditions, the treatments comprised various sowing depths (0 to 20 cm, at 2 cm intervals), with maximum emergence at 0 to 8 cm depth, with 80% of cocklebur emergence and higher speed emergence index (IVE); no emergence was observed below 16 cm.
Cocklebur; physiology