Primordium initiation at the stem apex as the primary event controlling plant development: preliminary evidence from wheat for the regulation of leaf development


*Correspondence and present address: R. K. M. Hay, Director, Agricultural Scientific Services. Department of Agriculture and Fisheries for Scotland, East Craigs, Edinburgh EH12 8NJ, U.K.


Abstract. The results from field studies of 12 crops of winter wheat (two seasons, four sites in the U.K., four cultivars), in which leaf appearance and events at the mainstem apex were fully documented, were used to investigate the inter-relationship between leaf initiation and appearance. It was shown that the progress of leaf appearance could be divided into two phases around collar initiation. During the first phase, which was common to all crops examined, leaf appearance was linearly related to leaf initiation, indicating that leaf appearance was not independently regulated by the environment but dependent on initiation. The slope of the second phase relationship varied between crops, indicating the intervention of an additional controlling factor. This shows that, for the first phase at least, the time course of leaf appearance was predetermined by the rate of leaf initiation at the stem apex.