Energy Supply and Light-enhanced Chloride Uptake in Wheat Laminae

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The light-supported component of 36Cl uptake from 5 mM K36Cl by green laminae, either chopped or vacuum-infiltrated, of Triticum aestivum L. seedlings has been determined by subtraction of dark uptake values from light uptake values and the energy sources for the uptake elucidated on the basis of the effects of 3-(3,4-dichlorophenyl)-1,1 dimethylurea (DCMU), carbonyl cyanide p-trifluoromethoxy-phenylhydrazone (FCCP), antimycin A1 (AA), and N2 on light and dark uptake. The light-supported Cl−1 uptake is shown to be partially inhibited by DCMU or AA but unaffected or stimulated by FCCP or N2. There is no additive effect on inhibition caused by DCMU + N2 or FCCP + AA but there is an added inhibition caused by DCMU + AA, DCMU + FCCP, and by FCCP or AA in anaerobic conditions. The effect of these inhibitors on photosynthetic gas exchange of chopped tissue has also been determined. On the basis of the results it is concluded that the uptake of Cl−, supported in the dark by oxidative phosphorylation, is enhanced by light and may be supported by cyclic and non-cyclic electron-flow energy. Uptake is not obligatorily linked to any one energetic pathway and there may be switching from one source to another.

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