Effects of herbicides on the light-activated,magnesium-dependent ATPase of isolated spinach (Spinacia oleracea L.) chloroplasts |
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| Authors: | William R Alsop Donald E Moreland |
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| Institution: | 1. Southern Region Agricultural Research Service, United States Department of Agriculture, Botany Department, North Carolina State University, Raleigh, North Carolina 27607 USA;2. Southern Region Agricultural Research Service, United States Department of Agriculture, Crop Science Department, North Carolina State University, Raleigh, North Carolina 27607 USA |
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| Abstract: | Isolated spinach (Spinacia oleracea L.) chloroplasts contain a Mg+2-dependent ATPase that is activated by light in the presence of dithiothreitol (DTT) and phenazine methosulfate (PMS). Effects of 11 herbicides, known to affect photophosphorylation in isolated chloroplasts, were measured on ATPase activity when added prior to illumination, on the postillumination dark activity of the ATPase, and on the light-induced synthesis of ATP mediated by DTT and PMS.When added prior to illumination, activity of the ATPase was stimulated by low, and inhibited by high, molar concentrations of chlorpropham, dicryl, dinoseb, ioxynil, oryzalin, perfluidone, propanil, and 4,6,7-trichloro-2-(trifluoromethyl)benzimidazole (TCTFB). The light activation of the ATPase was not affected by diuron, bromacil, or atrazine. Perfluidone, dinoseb, ioxynil, and TCTFB stimulated, whereas chlorpropham, dicryl, oryzalin, propanil, atrazine, bromacil, and diuron had no effect on postillumination hydrolytic activity. The light-induced synthesis of ATP mediated by DTT and PMS was inhibited strongly by chlorpropham, dicryl, dinoseb, ioxynil, oryzalin, perfluidone, propanil, and TCTFB.Because the ATPase reactions are considered to represent the reversal of the terminal reactions of photophosphorylation, inhibition of these reactions implies that the compounds tested, except for diuron, atrazine, and bromacil, have a site of action on the ATP-generating pathway that is separate from the site involved in the inhibition of the Hill reaction. |
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