Influence of putrescine on enzymes of ammonium assimilation in maize seedling

The effect of different concentrations of putrescine on biochemical changes in root and shoot of six days old maize seedlings in terms of enzymes of ammonium assimilation was examined. The results revealed that glutamate dehydrogenase (GDH) activity enhanced at lower concentration of putrescine but at higher concentration, the activity of this enzyme declined. Glutamine synthetase (GS) activity decreased with increase in concentration of putrescine and it was highest at 1000 μM concentration. However, glutamate synthase (GOGAT) activity increased with increase in concentration of putrescine upto 100 μM in root and upto 50 μM in shoot and further increase in concentration resulted in decline of enzymatic activity. Protein and total nitrogen content increased upto 10 μM concentration of putrescine and it decreased further with increase in concentration both in root and shoot of maize seedling, indicating maintenance of NH4⁺ concentration in root and shoot by low concentration of putrescine inducing NADH dependent GDH/GOGAT system. The non-NADH dependent GS continuously goes on detoxifying excess NH 4⁺ in the presence of increasing concentrations of putrescine.