EFFECT OF LIGHT IN THE GERMINATION OF WEED SEEDS

Seeds of weeds occurring in a cotton culture in Campinas, SP, Brazil, were collected. The sensitivity to light of seeds of 43 species belonging to 13 families was studied: 19 species were positive photoblastic, 6 species did not show photoblastism, 17 species could not have their photoblastic behaviour determined due mainly to low germination, and one species presented variable results. The possible reasons for the variation observed in the photoblastic behaviour of the weed seeds are discussed, as well as their ecological implications.