Zilkah, S., Department of Plant Genetics, Weizmann Institute of Science, Rehovot, Israel
Gressel, J., Department of Plant Genetics, Weizmann Institute of Science, Rehovot, Israel

Callus tissue has been isolated from 11 species, of 8 which are 'weeds' from which callus isolation has not been previously described. Continuous suspension cultures of four species have been started. Growth conditions were optimized for high yield. Logarithmic phase and stationary phase cells react differently to some inhibitors. The larger the inoculum size, the greater the concentration of inhibitor that must be used to achieve equal inhibition. Hormonal constitution of the medium affects inhibition by 'auxin' type herbicides. Growth kinetics, delayed response and recovery must be considered in assessing phytotoxicity. Highly uniform and controlled procedures are required for interspecific comparisons of many compounds. © 1977 Oxford University Press.