Physiological and Biochemical Studies in Plant Metabolism: Ii. Respiratory Enzymes in Wheat

Waygood, E. R.

doi:10.1139/cjr50c-002

Cited by 67 publications

(31 citation statements)

References 9 publications

(14 reference statements)

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“…There are strong reasons for believing that the bulk of this oxygen absorption is catalyzed by cytoehrome oxidase and the endogenous cytochrome c. The evidence in favor of this view is: (a) Phenoloxidase, which might be considered to be a possible catalyst for PPD oxidation, is apparently absent from these seedlings (12,20); the feeble oxygen absorption induced by the addition of catechol to the extracts is probably ascribable to the cytochrome system, with catechol acting as a reducing agent (18 Goodwin and Waygood (8).) However, in these cases, and indeed wherever it is feasible, it seems that the spectrophotometric method of measuring cytoehrome oxidase is greatly to be preferred, since not only is it more sensitive and direct, but it is independent of the endogenotis cvtochrome c.…”

Section: Discussionmentioning

confidence: 94%

“…Also Webster's recent survey (21) stressed the widespread distribution of this enzyme in dicotyledonous plants. Even (20) concluded that the oxidase is not present in extracts of wheat seedlings after the third day of development. Butler (4) reported inability to detect cytochrome oxidase in extracts from 5-day wheat roots, although Lundegardh (16), using a specially designed spectrophotometer, was able to observe characteristic cytochrome absorption bands in intact roots of older wheat.…”

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confidence: 99%

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Cytochrome Oxidase Content and Respiratory Rates of Etiolated Wheat and Barley Seedlings.

Fritz

Beevers

1955

Plant Physiol.

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Section: Discussionmentioning

confidence: 94%

mentioning

confidence: 99%

Cytochrome Oxidase Content and Respiratory Rates of Etiolated Wheat and Barley Seedlings.

Fritz

Beevers

1955

Plant Physiol.

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“…A situation similar to that for barley exists for older wheat roots from which Waygood (30) and Butler (4) were not able to extract an active preparation of cytochrome oxidase. The difficulty appears to be one of method since Lundegardh (18) has shown spectrophotometrically the existence of a functioning cytochrome system in intact wheat roots.…”

Section: Methodsmentioning

confidence: 99%

“…Waygood (30) found that dilute salt solutions eluted ascorbic oxidase from the residue of the centrifuged homogenate of wheat seedlings. The Moore roots were presoaked in 1.5 M glucose or in water for 1 hr, rinsed, and then homogenized in water.…”

Section: Methodsmentioning

confidence: 99%

Ascorbic Acid Oxidase in Barley Roots

Honda

1955

Plant Physiol.

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Two possible terminal metallo-oxidases have been found in barley, ascorbic oxidase by James and Cragg (14) and cytochrome oxidase by Merry and Goddard (23). Studies on the intracellular distribution of various ascorbic oxidases by Mandels (21) and Newcomb (25) indicated that the enzymes are localized at the surface. Newcomb (25) has shown that in many higher plants ascorbic oxidase is attached to or situated near the cell wall. According to the reviews of Goddard and Meeuse (7) and Goddard and Stafford (8), cytochrome oxidase is localized in the mitochondria. Thus, it may be possible to distinguish between ascorbic oxidase and cytochrome oxidase by their intracellular distribution. However, there are differing views on the intracellular distribution of cytochrome oxidase in higher plants. Lundeg'ardh (18) postulated a coating of cytochrome oxidase on the inner surface of the cell walls and in the tonoplast membrane of wheat roots, while Butler (3) considered that it is localized both in the tonoplast membrane and in the mitochondria. Lundegardh (18) suggested that the peripheral localization facilitates salt respiration and accumulation which have been found associated with the cytochrome system (17,31). An added complicatio.n raised by James (12) Homogenates of the root segments were prepared essentially by the method of Newcomb (25). Cellfree homogenates (25 % w/w) were obtained after grinding the roots for 3 to 5 minutes in either icechilled water or media initially 0.8 M tonicity and adjusted to 0.4 M final exogenous tonicity.Centrifugal fractionations of the homogenates were carried out in a refrigerated centrifuge at 0 to 20 C. The wall fragments were resuspended three times in the appropriate medium and the fragments resedi- Ascorbic oxidase and cytochrome oxidase were assayed by Warburg manometric procedures. Temperature equilibration was carried out for 30 minutes before the assay. Substrates and other reagents were then tipped into the main vessel compartments which contained 0.5 ml enzyme preparation, unless otherwise specified. Concentrations of reagents before and after substrate addition were maintained constant. Exogenous inorganic ions were usually excluded. For example, ascorbate was added as the acid form and not as the sodium or potassium salt. This accounts for the low pH in experiments completed before trishydroxymethyl-amino-methane (Tris.), an organic base, was available. In later experiments sufficient organic base was added to maintain the pH. The final pH values of the assay solutions after the last manometer readings were determined with glasscalomel electrodes.The activities quoted are corrected for non-enzymatic oxidation of substrates as computed from similar treatments either without the enzyme preparations or with heat inactivated preparations. No effects of tonicity on the activity were found. Consequently, precautions were not taken to assay activity under a given tonicity.Preparations of various ages were employed since the homogenate was relatively stable with more than...

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“…A number of workers have, however, suggested that ascorbic acid is concerned in the transport of hydrogen in respiratory metabolism, and that the two forms of ascorbic acid constitute an oxidation-reduction couple (Szent-Gyorgyi, 1931;Hopkins & Morgan, 1936;Straschitzki & Rubin, 1936;Crook, 1941;James & Cragg, 1943;James, Heard & James, 1944;Crook & Morgan, 1944;Waygood, 1950). Potato tissue does not appear to contain an enzyme system which can oxidize ascorbic acid directly (Johnson & Zilva, 1937), and the rapid oxidation of ascorbic acid to dehydroascorbic in potato extracts under aerobic conditions was presumed to be due to indirect oxidation by polyphenolase.…”

mentioning

confidence: 99%