Temperature response of vernalization in wheat: Modelling the effect on the final number of mainstem leaves

This paper outlines a modelling approach which predicts the effect of both continuous and intermittent low temperature regimes on the final number of leaves in winter wheat. The model takes account of the balance between the concurrent processes of leaf primordium initiation and rare of saturation of vernalization, and their response to temperature. The inverse of the time to saturation of vernalization, at which stage final leaf number is set, is modelled as a linear Function of vernalizing temperature. between 0 and 17 degrees C. The rate of leaf primordium initiation is modelled using the established linear relationship between rate and temperature above 0 degrees 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 rare towards floral transition at on-vernalizing temperatures (above 17 degrees 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(2) values of 70-90%, the final leaf number across a range of six to 21 leaves. Prediction of final leaf number for some cultivars was better in continuous than in intermittent vernalizing regimes. This modelling approach can explain the often-conflicting reports of the effectiveness of different temperatures for vernalization, and the interaction of plant age and vernalization effectiveness. (C) 1996 Annals of Botany Company.