Effects of TIBA, 2,4-D, Flurenol and CCC upon growth, root formation, membrane permeability, content of nucleic acids and stability of the chromatin were investigated. The four substances showed little or no effect on growth of isolated plant segments, but TIBA, 2,4-D and CCC caused 25–30 inhibition of growth of whole pea seedlings even at low concentrations. Root formation is inhibited by TIBA, Flurenol and 2,4-D, but not by CCC. At concentrations>10-4mol/l all the substances reduced the permeability of the plasma lemma, at lower concentrations only CCC and Flurenol still reduced permeability of the plasma lemma. The ratio RNA/DNA was decreased by TIBA, 2,4-D and Flurenol but it was increased by CCC. The Tm-value of isolated pea-chromatin was lowered by treatment with CCC and elevated by treatment with TIBA, 2,4-D and Flurenol can decrease or increase the Tm of isolated chromatin depending on their concentration. The results have shown that even very low concentrations of herbicides and growth retardants are able to induce metabolic alterations with partly unknown consequence
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