The Effects of 2:4-Dichlorophenoxyacetic Acid, 2:3:5-Tri-Iodobenzoic Acid, and Thiourea on the Vegetative and Reproductive Growth of Avena sativa

The effects of 2:4-dichlorophenoxyacetic acid (2:4-D), 2:3:s-tri-iodobenzoicacid (TIBA), and thiourea on the growth of Avena sativa havebeen studied in relation to subsequent leaf development, tillerproduction, and apical growth of the seedlings. Treatments with2:4-D and TIBA depressed the emergence of each successive shootingleaf, but thiourea, at the concentration used, proved to belethal. Subsequent observations on the tillering capacity ofthe seedlings show that treatment with 2I4-D significantly increasesthe rate of tiller production, but that TIBA fails to do so. Longitudinal sections through the apices of the treated seedlingsshow that both treatments have inhibited the development ofthe apex. 2I4-D inhibition is the greater. In the concentrationsapplied, neither treatment caused any obvious abnormalitiesin respect of mature leaves.