Effect of vernalization on the development and growth of Alopecurus myosuroides

Alopecurus myosuroides is an annual winter grass weed present in many winter and spring crops. The vernalization responses of three populations of A. myosuroides were assessed using natural exposure during winter in two field experiments and using cold exposure of imbibed seeds in a refrigerator in two greenhouse experiments. It was observed that a period of chilling during the pregermination phase had a marked effect on subsequent phenology. In the greenhouse, the major effect of vernalization was the reduction in the vegetative period because of an early reproductive induction of the apex. Plant morphology was affected by vernalization via a decrease in biomass resulting from a reduced tiller number. In all experiments, the time to panicle emergence and the number of leaves on the main stem were reduced by the chilling treatment in field and greenhouse experiments. Alopecurus myosuroides appears to be a species with a partial (quantitative) requirement for cold vernalization, but polymorphism for vernalization requirement was observed within and between populations. Depending on the sowing date, 850–1200 day–degrees C were required for flowering. The possible existence of different annual life forms within A. myosuroides is discussed.