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Stimulation of H⁺ Efflux and Inhibition of Photosynthesis by Esters of Carboxylic Acids

Donna E. Duhaime and Alan W. Bown
Plant Physiology
Vol. 73, No. 3 (Nov., 1983), pp. 828-833
Stable URL: http://www.jstor.org/stable/4268342
Page Count: 6
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Since scans are not currently available to screen readers, please contact JSTOR User Support for access. We'll provide a PDF copy for your screen reader.
Stimulation of H⁺ Efflux and Inhibition of Photosynthesis by Esters of Carboxylic Acids
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Abstract

Suspensions of mechanically isolated Asparagus sprengeri Regel mesophyll cells were used to investigate the influence of various carboxyester compounds on rates of net H+ efflux in the dark or light and photosynthetic O2 production. Addition of 0.15 to 1.5 millimolar malathion, α-naphthyl acetate, phenyl acetate, or p-nitrophenyl acetate stimulated H+ efflux and inhibited photosynthesis within 1 minute. In contrast, the more polar esters methyl acetoacetate or ethyl p-aminobenzoate had little or no effect on either of these two processes. A 0.15 millimolar concentration of α-naphthylacetate stimulated the normal rate of H+ efflux, 0.77 nanomoles H+ per 106 cells per minute by 750% and inhibited photosynthesis by 100%. The four active carboxyester compounds also stimulated H+ efflux after the normal rate of H+ efflux was eliminated with 0.01 milligrams per milliliter oligomycin or 100% N2. Oligomycin reduced the ATP level by 70%. Incubation of cells with malathion, α-naphthyl acetate, or p-nitrophenyl acetate resulted in the generation of the respective hydrolysis products ethanol, α-naphthol, and p-nitrophenol. It is proposed that inhibition of photosynthesis and stimulation of H+ efflux result when nonpolar carboxyester compounds enter the cell and generate acidic carboxyl groups when hydrolyzed by esterase enzymes.

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