title: Stimulation of h efflux and inhibition of photosynthesis by esters of carboxylic acids.
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 O(2) production. Addition of 0.15 to 1.5 millimolar malathion, alpha-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 alpha-naphthylacetate stimulated the normal rate of H(+) efflux, 0.77 nanomoles H(+) per 10(6) 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% N(2). Oligomycin reduced the ATP level by 70%. Incubation of cells with malathion, alpha-naphthyl acetate, or p-nitrophenyl acetate resulted in the generation of the respective hydrolysis products ethanol, alpha-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.
authors: Agriculture Canada Research Station, Vineland Station, Ontario, Canada L0S 2E0.
authors: D E
authors: DE
authors: Duhaime
authors: A W
authors: AW
authors: Bown