Dinâmica do banco de sementes em uma comunidade de plantas daninhas com aspectos da germinação e dormência de sementes de capim-marmelada (Brachiaria plantaginea (Link) Hitch.)

Abstract

The size, species composition and temporal variation of Lhe seed bank in the soil of four weed fields in Lavras, MG., was evaluated using soil samples collected at 3-monthly intervals during one year. Differences in the soil stored seed niunber were found between the four fields and at each sample time. The emerged seedling number from the soil samples ranged from 10166 to 2 180190/m . A good correspondence was found between the species composition of the plant communities and the species found in the soil seed reserve. The number of seeds promptly germinable was higher than the number found in temperate zones. About 80% of the seeds was found accumulated in the 8 cm upper soil layer, while lower layer were richer on number of species. The seed longevity experiments demonstrated that about 3% of seeds mantained on the surface of soil and buried 10 cm deep, were stili viable after 20 weeks. The seeds of B. plantagxnea were dormants when harvested; they didn't require light to germinate but the seed coat scarification. The most effective treatment in dormancy breaking was the 15 t/o 60 minutes H2 SO4 immersion. GA3 ,KNO and chilling 2 4 3 3 ° treatments were innefficient in dormancy breaking.