HERBICIDES THE RELATIVE TOXICITY OF NITROPHENOLS TO VARIOUS ORGANISMS

The effect of increasing degrees of nitration on the toxicity of phenols was assessed by measuring the toxicity of phenol, o - and p -nitro phenols and 2:4-dinitro phenol with several different test organisms. Toxicity levels were determined by the concentration required in each case to bring about the following responses: (i) to halve the rate of radial growth of Trichoderma viride at pH 3, (ii) to halve the respiration rate of yeast at pH 3, (iii) to halve the rate of frond multiplication of Lemna minor at pH 5·4, (iv) to bring about 50% mortality of seedlings of Brassica alba in a spraying test and finally (v) to halve the rate of respiration of leaf disks of B. alba vacuum-infiltrated with the toxic solution at pH 3.