Activities of phosphofructokinase (PFK), fructose-1,6-bisphosphate aldolase (FBP aldolase) and pyruvate kinase (PK) increased progressively in the roots of flood-tolerant SSG-59-3 cultivar during flooding. In contrast, only a slight change in activities of PFK and FBP aldolase was discerned in the roots of flood-sensitive S-308 cultivar during initial stages of flooding followed by a decline in the activities of these enzymes. Although the activity of hexokinase (HK) was transiently elevated in roots of both the cultivars during flooding, the magnitude of increase was much more in SSG-59-3 than in the S-308. In leaves of SSG-59-3, HK activity increased during 12 h of flooding whereas only a minor change occurred in the case of S-308. Flooding resulted in depressed activities of PFK and PK in leaves of S-308 but that in SSG-59-3 rose following imposition of waterlogged conditions. Activity of FBP aldolase in leaves of tolerant cultivar also showed a steady enhancement during flooding. The total and reducing sugars content decreased in leaves and roots of the S-308 during flooding but in SSG-59-3 the amount was more or less comparable to that in corresponding non-flooded plants.

Flooding evoked a differential response in the activities of enzymes of fermentation pathway in leaves and roots of flood sensitive (S-308) and flood-tolerant (SSG-59-3) cultivars of sorghum. Activities of alcohol dehydrogenase (ADH), lactate dehydrogenase (LDH) and alanine aminotransferase (AlaAT) enhanced in roots of SSG-59-3 during 72 h of flooding. In contrast, a transient increase in the activities was discerned in roots of S-308 up to 24 h flooding followed by a decline in activities of these enzymes. In leaves of SSG-59-3, the activities of ADH and LDH increased to about three fold during flooding stress as compared to that in the non-flooded control plants. Though elevation in activities of these enzymes was observed in leaves of S-308 up to 48 h of flooding, the magnitude of enhancement was much lower than that in SSG-59-3. Alanine aminotranferase activity depressed in leaves of both the cultivars but the level of decline was more pronounced in sensitive cultivar S-308 as compare to tolerant SSG-59-3. The amount of alcohol, lactic acid and alanine were higher in both roots and leaves of SSG-59-3 than that in S-308 during flooding stress. It is thus apparent that roots and leaves of flood tolerant variety tends to attain greater capacity to perform reactions of various fermentation pathways to sustain production of ATP under flooded conditions.