TEMPERATURE EFFECTS ON COMMON COCKLEBUR (XANTHIUM STRUMARIUM L.) SEED GERMINATION

A better understanding of the seed ecology can be helpful for prediction of the potential of weed species to spread, for prediction of their invasiveness, and for development of more effective weed management strategies. In Serbia, in agricultural areas, edges of crop fields, as well as in uncultivated areas, more and more populations of common cocklebur (Xanthium strumarium L.) were detected. Seeds from two populations (P-1 and P-2) of this species were collected for testing temperature effects on germination. Germination tests were conducted in an incubator set to 10, 15, 20, 25, 30 and 35 degrees C, in the dark. The seeds were considered to be germinating at the moment of radicle emergence. The number of germinated seeds was recorded daily (germination rate) during 7 day period and germination rate (sum of germinations per day) was calculated. Final percentage of germination and seedlings length and weight were measured after 7 days of incubation. Seeds of the both common cocklebur populations did not germinate when incubated at 10 degrees C. The lowest germination occurred at 35 degrees C for population PI and at 15 degrees C for population P-2, while the maximum germination occurred at 25 degrees C for both populations. The highest length of seedlings were recorded at 25 degrees C and 30 degrees C for population P-1 and P-2, respectively, while the highest seedlings weight was at 35 degrees C for both populations. The lowest seedlings length, as well as weight, was measured at 15 degrees C for both populations.