Dormancy Breaking of Cocklebur (Xanthium strumarium L.) Seeds

In order to investigate the environmental factors including temperature, moisture, and plant hormones on dormancy breaking of seeds of Xanthium strumarium L. a number of experiments were conducted. X. strumarium seeds were dormant soon after being harvested. Seed germination of cocklebur increased through a combination of cooling, temperature fluctuations following ripening. Most seed germination (82.5%) occurred in buried seeds in 5-7 cm depths of soil in natural conditions for 4 months in addition to keeping them in cool room temperature (5±2) for 3 months, followed by retaining the seeds on the surface of soil (0 cm) in field conditions for 6 months. A combination of cold (5±2?C for 2 months) and GA3 resulted in a slight significant increase in seed germination of X. strumarium L. (p<0.05). Washing of seeds, immersing them in hot water and scarification (crust split of seeds) had no significant effect on seed germination. Sulfuric acid (%98), scarification and Ethephon did not show any effect on seed germination (p<0.05). In all the treatments, between two seeds treated through burring only the larger seeds germinated while none of the treatments resulted in the germination of smaller seeds. Based upon on the experimental treatments in this study, it can be said that dormancy of X. strumarium L. seeds is a physical as well as a physiological dormancy phenomenon.