Exploring the ammonium detoxification mechanism of young and mature leaves of the macrophyte Potamogeton lucens.

Toxicity in aquatic plants, caused by excess ammonium in the environment, is an important ecological problem and active research topic. Recent studies showed the importance of the enzyme Glutamate Dehydrogenase (GDH) in detoxifying ammonium. However, these results mainly derived from species comparisons, hence some mechanisms may have been obscured due to species differences. Our recent finding that young leaves of Potamogeton lucens were less sensitive to ammonium enrichment, than mature leaves allowed us to study ammonium detoxification within a species. We found that, unlike mature leaves, ammonium-tolerant young leaves of P. lucens could assimilate ammonium mainly through GDH. There was a 38% increase of NADH-dependent GDH in 50 mg/L ammonium concentration compared with 0.1 mg/L. Therefore, this study confirms the hypothesis that the GDH pathway plays a major role in the detoxification of ammonium in freshwater macrophytes.