COMPARISON OF THE MEASUREMENT OF THE IN-VIVO ACTIVITY OF THE ALTERNATIVE PATHWAY IN AGED POTATO-TUBER SLICES

Recently it was reported that the use of the hydroxamate-inhibiting me thod leads to an underestimation of the in vivo alternative pathway (A P) activity and its contribution to total respiration (V-t) in plants. However, there is still a dispute about the extent of these possible underestimations. In this paper the oxygen-isotope-discrimination (OID ) technique and the hydroxamate-inhibiting method have been compared f or aged potato (Solanum tuberosum L.) tuber slices. As a result, the i n vivo contributions of AP activity to V-t were calculated to be 15.7% and 16.8% with the hydroxamate-inhibiting method, and 30.2% and 34.9% with the OID method in slices aged for 12 and 24 h, respectively. The observed underestimations of about one-fold confirm the suggestions w ith respect to the unsuitability of the hydroxamate-inhibiting method for the determination of the in vivo AP activity.