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

Information is presented on the hierarchical relationship betweenthe stems of Proctor barley grown under controlled conditions.Rates of production of foliar and floral primordia and ratesof leaf unfolding were found to follow the order main-stem >primary tillers > secondary tillers. Apical dome size wasinitially substantially greater for the main-stem than for thetillers due principally to the slower transition of the latterto the reproductive condition; by the time that double ridgesare formed on the tiller apices apical dome sizes are similarto that of the main-stem. Transition to the reproductive conditionoccurs at about the same time for the primary tillers. Thisnear-synchrony results in a smaller number of leaves borne onsuccessive tillers, since these have had less time to initiatefoliar 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-stemand tillers is discussed.