The Connexion between Respiration and Salt Accumulation I. Preliminary Note

Butler, G. W.

doi:10.1111/j.1399-3054.1953.tb08438.x

Cited by 13 publications

(8 citation statements)

References 30 publications

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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%

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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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Section: Methodsmentioning

confidence: 99%

“…* Additional reagents were K-maleate, 4.6 x 102 M, adjusted to pH 7, and cyt c, 1.0 x 10' M. ** Concentration in 3.5 ml final volume was 6.4 x 10-'M.…”

Section: Methodsmentioning

confidence: 99%

Ascorbic Acid Oxidase in Barley Roots

Honda

1955

Plant Physiol.

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“…The direct demonstration of cytochrome oxidase in older wheat roots has also failed (4,28), although the characteristic absorption bands of the cytochromes have been observed in the intact roots (20); thus suitable procedures for extraction and assay may be difficult to find.…”

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Succinoxidase and Cytochrome Oxidase in Barley Roots

Honda

1955

Plant Physiol.

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“…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. Albaum and Eichel (1) demonstrated that the oxidase was present in extracts from oat seedlings one or two days old, but did not detect the enzyme in extracts from older seedlings (up to 6 days), and concluded that cytochrome oxidase operated only during the embryonic stages.…”

mentioning

confidence: 99%