‘Compartmentation’ of acids in plant tissues

The cells of higher plants, in contrast with those of other organisms, contain relatively large amounts of organic acids. Krebs & Lowenstein (1960) calcu- lated that the concentrations of individual organic acids in Escherichia coli are about 0-01 mM, in liver or kidney cells 0 1 mm, and in yeast cells 1 mm. By using the same type of calculation it can be esti- mated that many plant tissues contain citrate and malate at concentrations of 10 mm, and some contain aconitate or isocitrate at this concen- tration. Succinate and fumarate are often present at a concentration of 1 mm, but other acids occur at lower concentrations.