Effects of Nonionic Surfactants on Root Growth and Cation Uptake.

1 Revised manuscript received Sept. 9, 1963. 2 Paper 37, Plant Nutrition Laboratory. This work was supported by research grant RG-07339-02 from the National Institutes of Health. :'Present address: Division of Agricultural Developnihnt, Tennessee Valley Authority, VVilson Dam, Alabama. specified (8). In some cases it is known that a, mixture of molecular species may be present, and often the manufacturer may offer a numbered series of chemically-related preparations wvith progressively changing properties (8). Surfactant preparations are commonly solutions, with the percent of the active ingredients not always disclosed. The investigator is therefore often confronted Nwith some (lifficulties in expressing the concentration of surfactant present in a test solution. Frequently he can do no more than state this on a percent v/v basis, with somle unlcertainty that different batches of the product will be identical. Twenty-two nonionic surfactants were obtained from their respective manufacturers together with technical data which varied considerably in extent of detail. Some of the preparations from the sources listed below are believed to be similar with respect to general chemical groupings, and might be identica!. However, their effective concentration and other unspecified components may be different. In these studies surfactants were used in a number of testL systems at concentrations ranging from 0.001 to 0.10 % v/v which gave solutions witlh p1 close to 6.0. Trade names and clhemical types are given in table I.