The Control of Tillering in the Barley Plant II. The Control of Tiller-Bud Growth During Ear Development

Tho intoraction between grain number and the level of mineral nutrient supply in the control of tiller-bud elongation has been examined in two varieties of barley (cv. Pil'oline, free tillering; cv. CI. 3576, restricted tillering). It was found in Pil'oline that the level of the nutrient supply did not alter the effect of the grains, although a considerable increase in tillering at all levels of grain removal resulted from an increase in the mineral nutrient supply. In CI. 3576, on the other hand, increasing the nutrient supply decreased the influence of the grains although it required an extremely high nutrient supply to completely suppress the grain effect. The hypothesis that tillering in this variety was primarily controlled by competition between the grains and WIer buds for a limited nutrient supply was supported by an examination of the nitrogen contents of the grains and emel'ging tillers.