-(Seed germination of Dyckia tuberosa (Vell.) Beer (Bromeliaceae) under different temperature in light and darkness). The effects of temperature and light on the germination of seeds of Dyckia tuberosa (Vell.) Beer, a terrestrial bromeliad from "cerrado", were studied. Seeds collected at Estação Ecológica of Itirapina, São Paulo State, were incubated at constant temperatures in the range of 10 to 45 °C, under continuous white light and darkness. The range of temperature with highest germinability under light was from 15 to 40 °C and from 20 to 40 °C in darkness, with no germination at 10 and 45 ºC for light and darkness. For both, light and darkness, the optimum temperature was in the range of 30 to 35 °C. The high germinability at high temperatures shows that D. tuberosa is able to germinate in open areas and the light insensitivity of the seeds indicates that they can also germinate in conditions of completely darkness. Apparently, the germination process is not a limiting factor for this species.

ABSTRACT

Investigations were carried out to study the effect of light, temperature and water stress on the germination of seeds of Jacaranda mimosifolia which showed the minimum and maximum germination temperature at 15 and 40°C, respectively. The optimum temperature was 25°C with high percentage and germination rate. Slight promotive effect of white light was observed. Under water stress conditions the effect of light was high but at optimum temperature no effect of light was observed. At -0.9MPa few seeds germinated.

The effects of the temperature and light on the control of seeds germination in

The aims of this study were to evaluate the effects of light and temperature on seed germination and the effect of light on seedling emergence of Clausena excavata, an invasive exotic species. Seeds were incubated at constant temperatures (10 to 40 ºC), under continuous white light and darkness. Seedling emergence was evaluated under full sun and canopy shade. There was no significant difference between seeds germinated in the presence or absence of light at temperatures between 20 and 35 ºC. Seeds maintained at 20 ºC germinated more slowly than other temperatures. Independent of temperature, seed germination was much more synchronised under white light than under darkness. In the field, emergence occurred in both environments, but a greater percentage was observed under full sun. Seedling emergence occurred at the same rate and synchronisation index under both conditions. C. excavata has a high invader potential in open areas and shaded environments.