Effects of plant growth regulators on tiller bud outgrowth in uniculm cereals

Plant growth regulators were applied either to seeds or to leaves of uniculm selections of barley and wheat. None of the treatments stimulated the growth and development of tiller buds in the barley selection. In contrast, in wheat the development of tiller buds was readily stimulated and tillers were produced following treatment with Terpal, Cerone, TIBA or nitrate. In Terpal and Cerone treated plants, the stimulation of tiller bud outgrowth and tillering was accompanied by a marked retardation of growth in the main shoot. The growth of the tillers was however not sustained in any of the treatments, and so at maturity all plants were virtually uniculm. The results are discussed in relation to the different overall response of the two species, the death of tillers, and the hormonal regulation of tiller bud development.