Changes in Enzyme Levels of EMP and Pentose Phosphate Pathways during Germination of Cottonseed

Abstract

Changes in the levels of key enzymes in the two carbohydrate oxidative pathways were studied in cotyledons and radicles of germinating cottonseed. Prior to radicle emergence, PFK activity exceeded G6P dehydrogenase activity. Following radicle emergence, G6P dehydrogenase activity increased more than twofold, whereas PFK activity remained the same in cotyledons but apparently decreased in the radicles. The seemingly decreased levels of the EMP enzymes in radicles were due to a dilution of protein content during elongation. Enzymes of the EMP pathway were demonstrated only in radicle tips, while enzymes of the pentose pathway were demonstrable in both tips and elongating segments. We suggest that during the initial phases of germination, especially when oxygen diffusion may be restricted by the intact testa, the early and high requirement for ATP is met by substrate level phosphorylation from enhanced EMP activity. Differentiation in both elongating radicles and cotyledons, which in cotton become photosynth...