PHENOLIC-ACIDS AFFECT PHOTOSYNTHESIS AND PROTEIN-SYNTHESIS BY ISOLATED LEAF-CELLS OF VELVET-LEAF

The effects of p-coumaric, ferulic, chlorogenic, and vanillic acids on photosynthesis and protein synthesis by isolated leaf cells of velvetleaf (Abutilon theophrasti Medik) were investigated. Photosynthesis and protein synthesis were measured in cell suspensions by the incorporation of (CO2)-C-14 and [C-14]leucine, respectively. None of the tested phenolic acids except vanillic reduced photosynthesis by more than 50% at the highest concentration and 30 min of incubation. At 100 muM concentrations and 60-min incubation periods, p-coumaric, ferulic, chlorogenic, and vanillic acids inhibited photosynthesis by 33, 37, 57, and 65 %, respectively. Ferulic acid was the most inhibitory to protein synthesis and reduced the incorporation of [C-14]leucine by 50% at about 1.0 muM after 60 min of incubation. At the highest concentrations tested in this study, vanillic and ferulic acids were inhibitory to photosynthesis and protein synthesis, respectively, whereas chlorogenic and p-coumaric acids did not inhibit either physiological process. The maximum inhibition of protein synthesis by chlorogenic acid was 19% and by vanillic acid was 28% at 100 muM concentrations. Chlorogenic, vanillic, and p-coumaric acids at 0.1 muM caused increased protein synthesis over the untreated control. Overall, photosynthesis was more sensitive than protein synthesis to the four phenolic acids tested.