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Glycolytic and pentose phosphate pathway activity of Erythrina caffra seeds during anaerobic germination

J. Pretorius,K. Kemp,J. Small

Published 2002 in South African Journal of Botany

ABSTRACT

Seeds from only six species are known to germinate under anoxia of which Erythrina caffra Thunb. is the only dicot species found on dry land. It has been suggested in the past that seeds displaying a Pasteur effect are usually intolerant of anaerobic conditions. Although a Pasteur effect has been reported for Erythrina caffra seeds, the present study precludes this effect. In contrast, Pisum sativum seeds exhibit a strong Pasteur effect but are unable to germinate under anoxia. Anaerobic pre-treatment of Erythrina seeds enhanced the capacity of the oxidative pentose phosphate (OPP) pathway of axes. Glycolytic rates under aerobic and anaerobic conditions were similar. However, the amounts of glycolytic intermediates such as G-6-P, F-6- P, F-1,6-bisP, DHAP and GlycAld-3-P, in axes excised from air and N 2 treated E . caffra seeds, differed sufficiently to indicate that glycolysis occurs faster in axes under aerobic than anaerobic conditions. The release of 14 CO 2 by axes and cotyledons from air-treated E . caffra seeds, after labelling with [U- 14 C]-glucose, was also much higher than that from N 2 -treated seeds. In P sativum seeds, however, the opposite was true. Under anaerobic conditions it is expected that substrate level phosphorylation would be the main or only source of ATP production. Yet, increased activities were measured for phosphoenolpyruvate (PEP) phosphatase and phosphofructokinase (PFK), which bypass pyruvate kinase (PK) and PPi-dependent phosphofructokinase (PFP), respectively, in the glycolytic pathway. Collectively this data indicated that Erythrina caffra axes are able to utilise an alternative route for ATP production.

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