In this work, the ammonium-tolerant duckweed Landoltia punctata 0202 was used to study the effect of ammonium stress on carbon and nitrogen metabolism and elucidate the detoxification mechanism. The growth status, protein and starch content, and activity of nitrogen assimilation enzymes were determined and the transcriptional levels of genes involved in ion transport, and carbon and nitrogen metabolism were investigated. Under high ammonium stress, the duckweed growth was inhibited, especially when ammonium was the sole nitrogen source. Ammonium might mainly enter cells via low-affinity transporters. The stimulation of potassium transport genes suggested sufficient potassium acquisition, precluding cation deficiency. In addition, the up-regulation of ammonium assimilation and transamination indicated that excess ammonium could be incorporated into organic nitrogen. Furthermore, the starch content increased from 3.97% to 16.43% and 26.02% in the mixed-nitrogen and ammonium-nitrogen groups, respectively. And the up-regulated starch synthesis, degradation, and glycolysis processes indicated that the accumulated starch could provide sufficient carbon skeletons for excess ammonium assimilation. The findings of this study illustrated that the coordination of carbon and nitrogen metabolism played a vital role in the ammonium detoxification mechanism of duckweeds.

在这项工作中，耐氨性浮萍Landoltia punctata0202被用于研究铵胁迫对碳和氮代谢的影响并阐明解毒机理。测定其生长状况，蛋白质和淀粉含量以及氮同化酶的活性，并研究参与离子迁移，碳和氮代谢的基因的转录水平。在高铵盐胁迫下，浮萍的生长受到抑制，尤其是当铵盐是唯一的氮源时。铵可能主要通过低亲和力转运蛋白进入细胞。钾转运基因的刺激表明足够的钾吸收，排除了阳离子缺乏。此外，铵同化和氨基转移的上调表明过量的铵可掺入有机氮中。此外，在混合氮基和铵氮基中，淀粉含量分别从3.97％增加到16.43％和26.02％。淀粉合成，降解和糖酵解过程的上调表明，积累的淀粉可以为过量的铵同化提供足够的碳骨架。这项研究的结果表明，碳和氮代谢的协调在浮萍的铵盐解毒机理中起着至关重要的作用。