The effects of elevated atmospheric CO2 on lipid metabolism in leaves from mature wheat (Triticum aestivum cv Hereward) plants

Winter wheat (Triticum aestivum L. cv. Hereward) plants were grown for 35 d either at 350 μmol mol–1 CO2 or at 650 μmol mol–1 CO2. Lipid synthesis was studied in these plants by incubating the 5th leaf on the main stem with [1–14C]acetate. Increased CO2 concentrations did not significantly affect the total incorporation of radiolabel into lipids of whole leaf tissue, but altered the distribution for individual lipid classes. Most noticeable amongst acyl lipids was the reduction in labelling of diacylglycerol and a corresponding increase in the proportion of phosphatidylcholine labelling. In the basal regions, there were similar changes and, in addition, phosphatidylglycerol labelling was particularly increased following growth in an enriched CO2 atmosphere. The stimulation of labelling of the mitochondrial‐specific lipid, diphosphatidylglycerol, prompted an examination of the mitochondrial population in wheat plants. Mitochondria were localized in intact wheat sections by immunolabelling for the mitochondrial‐specific chaperonin probe. Growth in elevated CO2 doubled the number of mitochondria compared to growth in ambient CO2. Fatty acid labelling was also significantly influenced following growth at elevated CO2 concentrations. Most noticeable were the changes in 16C:18C ratios for the membrane lipids, phosphatidylcholine, phosphatidylglycerol and monogalactosyldiacylglycerol. These data imply a change in the apportioning of newly synthesized fatty acids between the ‘eukaryotic’ and ‘prokaryotic’ pathways of metabolism under elevated CO2.