Developmental Regulation of Respiratory Activity in Pea Leaves.

The developmental pattern of mitochondrial respiratory activity in pea (Pisum sativum) leaves has been investigated in an attempt to determine changes in mitochondrial function as plant cells mature. NADH and succinate dehydrogenase and cytochrome c oxidase activities remained relatively constant during cell maturation (from d 0 to d 14). Alternative oxidase and glycine decarboxylase activity, however, were low in young leaf tissue (d 0-6) but increased substantially as the tissue matured (d 7-14) and gained photorespiratory activity. Western blot analysis of the alternative oxidase protein revealed that it was primarily in an oxidized state in young leaves (d 0-6) but switched dramatically to the reduced form of the protein as the pea cells matured (d 7-14). The switch to the reduced form of the protein correlated with an increase in alternative oxidase activity. Results are discussed in terms of the changing function of plant mitochondria during leaf development.