Studies in phytotoxicity. II. Changes in the concentrations of tricarboxylic acid cycle intermediates associated with phytotoxic effects on leaves

Leaves of dwarf bean and blackcurrant were analysed for their content of some of the acids of the tricarboxylic acid (TCA) cycle after treatment with lime sulphur in order to correlate any changes with the increase in respiration previously reported. In the dwarf bean, a rapid initial decrease in succinic acid was followed by a large increase. This suggested that there was some blocking of the succinic dehydrogenase by the toxic agent. However it is probably important to consider the contribution of the hexose monophosphate (HMP) shunt in the increased respiration and associated metabolic changes as it has been shown that many disruptive agents, both chemical and biological, favour respiration by the HMP rather than the TCA route in plants.