Significant Stages of Ear Development in Winter Wheat

Abstract

Wheat growth and yield simulation models often have an element which traces plant development, generally by taking a few selected development stages and estimating the time which elapses between them. The criteria which are used to select these stages, and thus the phases of development which they demarcate, are considered in this paper. Specific stages may be selected because they have some fundamental importance in the physiology of the plant and may signal a change from one phase of growth to another; for example, the onset of stem elongation, which may affect the partitioning of resources to other organs in the plant. Specifying stages that define the duration of a particular process allows numbers of parts formed to be estimated if a prediction of the rate of the process can also be made; for example, Rahman and Wilson (1978) have analysed numbers of spikelets per ear in terms of rate and duration between specified morphological stages (double ridge and terminal spikelet). It may also be necessary to identify developmental stages when there is a change in the response of development or growth to certain environmental factors; for example, after anthesis, development depends only on temperature and it does not respond to daylength, which affects the preceding phases of the life cycle.