The objective of this work was to evaluate the effect of light and temperature on the germination of three common Brazilian weed species: Alternathera tenella, Conyza bonariensis and Digitaria ciliaris. The influence of four temperature variations (15/25, 20/30, 20/35 and 30/40 ºC) with and without light was tested on germination percentage and germination velocity rate (GVR). The seeds were collected in experimental seedbeds to allow sample homogenization. Fifty seeds of each species were placed in gerbox type boxes, previously prepared with humidified "germitest" germination double layer paper. The boxes were stored in temperature-controlled BOD type vertical germinators. The temperatures were maintained at the ratio of 16/8 hours day and night, respectively. Evaluations started three days after incubation, with the seeds displaying roots equal or over 1 mm being considered to have germinated. A significant light effect on germination was confirmed fort all the species, mainly D. ciliaris. A. tenella, presented high germination at all temperatures tested, even though 30/40 ºC restricted C. bonariensis germination. The treatments also affected GVR, whose behavior was similar to the germination percentage, with the highest effect being confirmed in D. ciliaris.
photoblastic seeds; germination velocity; weeds
