Abstract

To further investigate the recently observed invasion of a new weed in the São Paulo areas, Brazil, we studied the germination performance and emergence characteristics of Bidens sulphurea. We measured the seed germination under different fixed temperatures (15, 20, 25, 30 and 35°C), photoperiods (18h/6h, 12h/12h, 6h/18h and 0h/24h [light/dark], respectively), light quality (white, blue, yellow, green, red and dark condition); and emergence in two seasons (winter and spring) in different sowing depths (0, 1, 3, 5, 7 and 9 cm). This species has the ability to germinate and emerge above 90% in a range of conditions of light, but it is very sensitive to variations in temperature, and several reductions on its germination and emergence are found bellow 20°C. The emergence of this species is severely controlled by seasonality and could occur up to 9 cm depth in Brazilian spring.

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