Abstract

Root tissue slices of Beta vulgaris were aged by aerated mixing for 5 d in 0.1 mM CaSO₄ solution with and without 0.5 mM salicylate (pH 7.0). Mitochondria, isolated from treated and fresh beetroot tissue, were investigated, and the activities of the NAD(P)H oxidising pathways of the mitochondrial inner and outer membranes, together with the activity of the alternative pathway, were measured. From these we determined which non-phosphorylating pathways of mitochondrial respiration were induced by the treatments. The presence of salicylate in the ageing treatment was shown to increase the activity of the alternative pathway as well as the level of alternative oxidase protein. This increase was above that seen in the ageing treatment alone. Investigation of the other non-phosphorylating pathways of mitochondrial respiration indicated that while they also increased during ageing, they were not specifically affected by salicylate treatment. The specific induction of the alternative pathway increased activity by almost 4-fold from the fresh tissue and 2-fold from the aged tissue rates.