This paper outlines a modelling approach which predicts the effect of both continuous and intermittent low
temperature regimes on the ®nal number of leaves in winter wheat. The model takes account of the balance between
the concurrent processes of leaf primordium initiation and rate of saturation of vernalization, and their response to
temperature. The inverse of the time to saturation of vernalization, at which stage ®nal leaf number is set, is modelled
as a linear function of vernalizing temperature, between 0 and 17 °C. The rate of leaf primordium initiation is
modelled using the established linear relationship between rate and temperature above 0 °C. Final leaf number is
hence the product of the number of leaf primordia initiated once vernalization is saturated. In the model, genotypes
are characterized by (1) the slope and intercept of the linear response of the rate of saturation of vernalization to
temperature in the vernalizing range, and (2) by a development rate towards ¯oral transition at on-vernalizing
temperatures (above 17 °C). The model is tested against data from experiments where six cultivars of winter wheat
plants of different ages were exposed to a range of low temperature regimes, including continuous and intermittent
vernalizing temperatures. Overall, the model predicted, with r
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values of 70±90%, the ®nal leaf number across a
range of six to 21 leaves. Prediction of ®nal leaf number for some cultivars was better in continuous than in
intermittent vernalizing regimes. This modelling approach can explain the often-con¯icting reports of the effectiveness
of different temperatures for vernalization, and the interaction of plant age and vernalization effectiveness.