Activity of the Pentose Phosphate and Glycolytic Pathways During Anaerobic Germination ofEchinochloa crus-galli(barnyard grass) Seeds

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Abstract
Changes in the activity of key enzymes in glycolysis and the oxidative pentose phosphate pathway were studied in Echinochloa crus-galli (L.) Beauv. var. oryzicola seeds during germination in air or nitrogen. In addition, the metabolism of specifically labelled [I4C]glucose was followed to evaluate the activity of both pathways during anaerobic germination. During the 7 d time period studied there was no difference between air and nitrogen in phosphofructokinase activity. Under anaerobic conditions, fructose-1, 6-bisphosphate aldolase increased more than two-fold in 7 d; whereas in air, it decreased. The activity of the pentose phosphate pathway enzyme, glucose-6-phosphate dehydrogenase, increased under N2 until day three, when it levelled off, whilst it continued to increase up to day seven in air. Incubation of Echinochloa seedlings with specifically labelled glucose also resulted in differences between anaerobic- and air-grown seedlings. Labelling of phosphorylated sugars and lipids predominated under N2; whereas in air, malate and fumarate were the most heavily labelled compounds. In both air and N2, there was a greater percentage of label in CO2 from [l-14C]glucose, while [6-14C] resulted in a greater percentage label in ethanol. These differences were more pronounced under N2, especially during the first 24 h of imbibition, suggesting increased activity of the pentose phosphate pathway.