Further studies on autoclaved‐induced toxicity in tissue culture media: gauging sugar breakdown by spectrophotometry

Fructose and sucrose were used to investigate cyanide‐induced absorption changes after high temperature treatment. By comparing the time‐resolved absorbance difference spectra obtained under aerobic conditions with those under aerobic conditions, absorbance changes that are associated with the process of oxygen consumption were identified. The rates of absorbance changes of autoclaved sucrose solution or of autoclaved MS medium (Murashige and Skoog 1962. Physiol. Plant. 15: 473–497) were correlated with those of oxygen consumption measured by polarography and used for determining the toxicity of culture media (Hsiao and Bornman 1991. Physiol. Plant. 81: 55–58). When autoclaved together with sucrose, FeNa‐EDTA promotes its degradation. Absorbance change, therefore, is a convenient parameter for measuring not only the extent of carbohydrate breakdown at high temperature but also the relative toxicity of culture media autoclaved under different conditions.