AbstractA conceptual basis for modelling leaf tissue dynamics in temperate and tropical forage grasses was developed, identifying the key morphological plant parameters that determine the efficiency of herbage utilization in a grazing system. Topics explored include: the dynamics of leaf tissue production as resulting from morphogenetic responses of plants to environmental and sward state conditions; the temporal links between the dynamics of leaf production and senescence; and the role of the intensity and frequency of defoliation in the optimization of the balance between leaf tissue consumption and senescence.