Occurrence of Alternative Respiratory Pathway in Freshly Excised Apple Root Tissue

in Journal of the American Society for Horticultural Science
Authors:
S.Y. WangFruit Laboratory, Agricultural Research, U.S. Department of Agriculture, Beltsville, MD 20705

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G.L. SteffensFruit Laboratory, Agricultural Research, U.S. Department of Agriculture, Beltsville, MD 20705

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M. FaustFruit Laboratory, Agricultural Research, U.S. Department of Agriculture, Beltsville, MD 20705

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Abstract

A cyanide-resistant alternative pathway was found to exist in root tissue of apple (Malus domestica Borkh.). In the absence of potassium cyanide (KCN), an inhibitor of cytochrome electron transport, the alternative pathway did not contribute to overall root respiration. However, in the presence of KCN or carbonyl cyanide m-chlorophenyl hydrazone (CCCP), an uncoupler, active participation of the alternative pathway was detected. Inhibition of O2 uptake by salicylhydroxamic acid (SHAM) was observed in the presence of antimycin A (AA) or sodium azide (NaN3), but to a lesser degree than when KCN was present. The degree of inhibition by SHAM was greatest in the presence of KCN, followed by AA and then NaN3. The antioxidant n-Propyl gallate (PG) was found to be an effective inhibitor of the alternative pathway. The site of inhibition in apple root tissue by PG is very similar to that of SHAM. Sodium benzoate, another antioxidant and free radical scavenger, and tetraethylthiuram disulfide (disulfiram), a copper chelator, did not inhibit the alternative pathway in apple root tissue.

Contributor Notes

Received for publication May 5, 1983. Use of a company or product name by the department does not imply approval or recommendation of the product to the exclusion of others which also may be suitable. The cost of publishing this paper was defrayed in part by the payment of page charges. Under postal regulations, this paper therefore must be hereby marked advertisement solely to indicate this fact.

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