Germination responses to water potential in Bromus sterilis L. under different temperatures and light regimes

Abstract

Barren brome (Bromus sterilis L.) is a troublesome weed of winter cereals in western and central Europe and its control requires an exact estimation of emergence time. The study focused on the germination response of populations from the Czech Republic to water availability at different temperatures and under different light regimes. Seeds were able to germinate even at very low water potential (Ψ) close to the wilting point, but decreasing temperatures below 25°C and exposure to light decreased the germination percentage (GP) and prolonged the time to reach 50% germination (T₅₀). At higher temperatures of 15, 20, and 25°C, seeds germinated up to a Ψ value of–1.5 MPa; however, the GP differed between light (0–3%) and darkness (50–75%). At the highest temperature of 25°C and germination in water, T₅₀ was less than 1 day, but a decrease in Ψ to –1.5 MPa prolonged the T₅₀ to<br /> 5 days; however, this occurred without any significant effect of light regime. With decreasing temperature and Ψ, seeds were more sensitive to the light regime and the disproportion between T₅₀ in light and darkness increased. At a Ψ of less than –1.0 MPa, seeds needed twice as long for germination in light than in darkness when germinating at 20°C or 15°C. The results may be of value for the development of predictive models and for identifying times when weed control may be the most effective.