John Wiley & Sons, Ltd.

The effect of ammonia stress on nitrogen metabolism of Ceratophyllum demersum

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The objective of this paper was to determine the effect of total ammonia N concentration and pH on the N metabolism of Ceratophyllum demersum and to evaluate the stress caused by inorganic N enrichment in the water column on submersed macrophytes. In this experiment, pH values were carefully controlled to distinguish between the effects of un‐ionized NH3 and ionized NH4+. The results showed that the most obvious consequence of ammonia addition was an overall increase in ammonia content and decrease in nitrate content in all tissues of fertilized plants. The activities of nitrate reductase and glutamine synthetase were inhibited by long‐term ammonia addition. At the same time, ammonia addition significantly decreased soluble protein content and increased free amino acid content in all treatments. Another clear effect of ammonia addition was a decrease in carbon reserves. Therefore, the authors concluded that increased ammonia availability could affect plant survival and lead to a decline of C. demersum proliferation through a decrease in their carbon reserves. This interaction between N and C metabolism helps to explain changes in benthic vegetation due to steadily increasing coastal water eutrophication. This article is protected by copyright. All rights reserved

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