limitation of Alternative Respiratory Pathway Activity in Grapefruit Flavedo Tissue by Oxygen Availability

The capacity of the alternative respiratory pathway increased in the flavedo tissue of ;Marsh' grapefruit (Citrus paradisi Macf.) stored at 5 degrees C for 2 weeks or longer. Elevated O(2) levels during respiratory assays enhanced respiration by the tissue at 20 degrees C but not at 5 degrees C. At 20 degrees C, salicylhydroxamic acid alone was inhibitory to O(2) uptake only in elevated O(2). In conventional Warburg studies, alternative pathway respiration may be limited by the low solubility and/or slow rate of O(2) diffusion into plant tissues, such as grapefruit flavedo, and may be responsible for the apparent low utilization of the alternative pathway potential observed in other studies.