Ecologia da germinação e emergência de capim-amargoso

Abstract

Sourgrass is a species with high invasive capacity in agroecosystems, outstanding for its high germinative power and tolerance to the herbicide glyphosate that are responsible for considerable losses in agricultural productions. Despite its importance, studies on the ecology of germination and species emergence are still scarce. The present work aimed to evaluate the germination behavior in different water and salinity conditions, besides the emergence of the seedlings from the sowing at different depths. Experiments were carried out in the laboratory with seeds collected in the field, recording the effect of treatments on the number of normal and abnormal seedlings, quiescent and dead seeds. The bioassays were conducted in BOD-type germination chambers at alternating temperatures of 20 and 35° C with photoperiod with alternating cycles of day/night of 12/12 hours. Negative osmotic potentials reduced the germination of D. insularis and increased quiescence. There was complete suppression of the germination from the osmotic potential of - 0.80 MPa. The number of normal and abnormal seedlings was also influenced by the osmotic potential of the solution. Salinity had an effect on germination, with reduction of germination from 20 mM NaCl concentrations. Salinity also had effects on the generation of normal and abnormal seedlings and quiescent seeds. It was not possible to establish satisfactory mathematical models for seed mortality. Seed emergence was influenced by sowing depth, and the highest emergence values were observed in seeds placed on the surface of the substrate, while at 8 cm depth there was no emergence of plants. The set of results allows to conclude that the germination of the sourgrass presents resistance to low osmotic potentials and the toxicity of the salinity, and that in addition, despite the seeds of small size and with few reserves, it can emerge from depths of up to 8 cm, justifying its occurrence and difficulty of control in agricultural areas.