DIFFERENTIAL CARBON-MONOXIDE SENSITIVITY OF CYTOCHROME-OXIDASE IN THELEAVES OF TALL AND DWARF WHEAT CULTIVARS

Differential response in the leaves of tall and dwarf wheat to CO, an inhibitor of cytochrome oxidase and to SHAM, an inhibitor of alternati ve oxidase appears to be correlated with presence of Rht dwarfing gene s. This was detected by in vivo nitrate reductase assay after CO treat ment and direct O-2 uptake in presence of SHAM. Pretreatment of the le aves with Triton X-100 at a concentration which specifically inhibits the accessibility of exogenous NAD(P)H to alternative oxidase, signifi cantly enhanced the CO response as assessed by in vivo NR assay. This supports the hypothesis that the competition for NADH between NR and m itochondrial respiration is regulated by NADH-dehydrogenase located on the outer surface of inner mitochondrial membrane.