THE EFFECTS OF ELEVATED ATMOSPHERIC CO2 ON LIPID-METABOLISM IN LEAVESFROM MATURE WHEAT (TRITICUM-AESTIVUM CV HEREWARD) PLANTS

Winter wheat (Triticum aestivum L. cv, Hereward) plants were grown for 35 d either at 350 mu mol mol(-1) CO2 or at 650 mu mol mol(-1) CO2. L ipid synthesis was studied in these plants by incubating the 5th leaf on the main stem with [1-C-14]acetate. Increased CO2 concentrations di d not significantly affect the total incorporation of radiolabel into lipids of whole leaf tissue, but altered the distribution for individu al lipid classes. Most noticeable amongst acyl lipids was the reductio n in labelling of diacylglycerol and a corresponding increase in the p roportion of phosphatidylcholine labelling. In the basal regions, ther e were similar changes and, in addition, phosphatidylglycerol labellin g was particularly increased following growth in an enriched CO2 atmos phere. The stimulation of labelling of the mitochondrial-specific lipi d, diphosphatidylglycerol, prompted an examination of the mitochondria l population in wheat plants. Mitochondria were localized in intact wh eat sections by immunolabelling for the mitochondrial-specific chapero nin probe. Growth in elevated CO2 doubled the number of mitochondria c ompared to growth in ambient CO2. Fatty acid labelling was also signif icantly influenced following growth at elevated CO2 concentrations. Mo st noticeable were the changes in 16C:18C ratios for the membrane lipi ds, phosphatidylcholine, phosphatidylglycerol and monogalactosyldiacyl glycerol. These data imply a change in the apportioning of newly synth esized fatty acids between the 'eukaryotic' and 'prokaryotic' pathways of metabolism under elevated CO2.