Laboratory experiments were conducted to determine the effect of light, oxygen, and submergence on bur beggarticks seed germination. Fresh and dry stored seeds exhibited dormancy, requiring thiourea and light for germination. Red light was more effective than far-red or blue light in breaking dormancy. Both an oxygen-saturated and anoxic atmosphere completely inhibited germination. Hypoxic conditions (5 and 10% oxygen) led to an increase in germination compared to normoxia (21% oxygen). Primary dormancy was eliminated by 1 yr of soil burial. Seeds exhumed after soil burial had greater germination percentage than fresh or lab-stored seeds after a brief far-red irradiation, but did not germinate in the dark. The induction of secondary dormancy increased with increasing durations of submergence. Finally, sowing at different soil depths (0 to 8 cm) showed that germination and emergence occurred mainly with shallow burial (0.5 to 1.0 cm).
