A Comparison of Main-stem and Tiller Growth in Barley; Apical Development and Leaf-unfolding Rates

Abstract

Information is presented on the hierarchical relationship between the stems of Proctor barley grown under controlled conditions. Rates of production of foliar and floral primordia and rates of leaf unfolding were found to follow the order main-stem > primary tillers > secondary tillers. Apical dome size was initially substantially greater for the main-stem than for the tillers due principally to the slower transition of the latter to the reproductive condition; by the time that double ridges are formed on the tiller apices apical dome sizes are similar to that of the main-stem. Transition to the reproductive condition occurs at about the same time for the primary tillers. This near-synchrony results in a smaller number of leaves borne on successive tillers, since these have had less time to initiate foliar primordia, and a measure of synchrony in awn appearance, since rates of car development are similar for these stems. The nature of the hierarchical relationship between main-stem and tillers is discussed.