Title: Effect of Glyoxylate on the Sensitivity of Net Photosynthesis to Oxygen (the Warburg Effect) in Tobacco
Abstract:The addition of glyoxylate to tobacco (Nicotiana tabacum) leaf discs inhibited glycolate synthesis and photorespiration and increased net photosynthetic 14CO2 fixation. This inhibition of photorespira...The addition of glyoxylate to tobacco (Nicotiana tabacum) leaf discs inhibited glycolate synthesis and photorespiration and increased net photosynthetic 14CO2 fixation. This inhibition of photorespiration was investigated further by studying the effect of glyoxylate on the stimulation of photosynthesis that occurs when the atmospheric O2 level was decreased from 21 to 3% (the Warburg effect). The Warburg effect is usually ascribed to the increased glycolate synthesis and metabolism that occurs at higher O2 concentrations. Photosynthesis in control discs increased from 59.1 to 94.7 micromoles of CO2 per gram fresh weight per hour (a 60% increase) when the O2 level was lowered from 21 to 3%, while the rate for discs floated on 15 millimolar glyoxylate increased only from 82.0 to 99.7 micromoles of CO2 per gram fresh weight per hour (a 22% increase). The decrease in the O2 sensitivity of photosynthesis in the presence of glyoxylate was explained by changes in the rate of glycolate synthesis under the same conditions.Read More