Ageratum conyzoides is a weed with tropical origin that shows expressive presence in the seedbanks where it occurs. Considering the importance of knowing the factors that affect seed germination in weed species management, the effect of light and KNO3 at constant and alternating temperature on Ageratum conyzoides seed germination was evaluated. Four sub samples of 75 seeds for each treatment were submitted to the factorial combination of light (darkness; 12 hours light) and KNO3 (0% KNO3; 0,2% KNO3) for the assay at 25°C constant and at 15ºC/35ºC for 12h/12h in a randomized complete block design. Germination occurrence was evaluated daily for 21 days. At constant temperature, light promoted the percentage and the speed of germination and KNO3 reduced the germination percentage and speed of A. conyzoides seeds in darkness. The curve of accumulated germination was adjusted to the exponential model at constant temperature. At alternating temperatures, KNO3 with light increased the germination percentage and speed of A. conyzoides seeds. At alternating temperatures, the cumulative germination curve was adjusted to the logistic model, demonstrating higher asynchrony in seeds germination in time than at constant temperature.
curve of accumulated germination; dormancy; whiteweed; KNO3; germination speed
