On the effect of dinitrophenol on carbohydrate activation in higher plant tissues. —Previous investigations on the effects of 2,4 dinitrophenol (DNP) on carbohydrate metabolism in isolated pea internodes and in yeast showed that the increased rate of glycolysis induced by the uncoupler corresponds to an increased rate of the conversion of free hexoses and polysaccarides to hexose phosphates. In yeast about 30% of the radioactivity supplied and taken up as14C labelled glucose, and 20% of that supplied and taken up as glycerol is recovered as soluble sugar and glycogen; this phenomenon is almost completely suppressed by 10-4M DNP.