by S.portulacastrum was more delayed and weaker than that of nitrate 
The uptake process of N conformed to the first-order reaction kinetic model, and the absorption rate constant (k=0.023 5 /d) of ammonia was lower than that of nitrate (k=0.069 7 /d) of nitrate. The absorption of phosphorus was 1.87 times higher in the SA group compared to the SN group. The sea purslane has high tolerance to ammonia. The growth traits between the two groups did not showed any significant differences, with an exception of reduced stem biomass in the SA group. By using Eukaryotic Orthologous Groups(KOG) annotation, Kyoto Encyclopedia of Genes and Genomes(KEGG), and Gene Ontology(GO) pathway analyses, differentially expressed genes related to nitrogen metabolism in S. portulacastrum were screened, including nitrate reductase (NR), nitrite reductase (NiR), nitrate transporter (NRT1), chloride channel protein (CLC-c), slow anion channel (SLAH3), amino acid transporters, and aminotransferases. Among them, NR and NiR futher induced corresponding changes in protein expression levels. Compared with the SN group, NR and NiR expression levels in the levels of SA group were downregulated. This suggested that ammonia was assimilation did not occur mostly in the leaves, but the assimilation of nitrate mainly occurred in the leaves. The upregulated expression of aminotransferases (e.g., BCAT2, ALAAT2, AAT) and amino acid transport proteins (e.g., CAT1, Avt1H, BAT1, AATL1) suggests that ammonium from ammonium assimilation might be reallocated and recycled in the leaves. The upregulated gene expression of nitrate transporters such as NPF6.2/NRT1.4, NPF6.4/NRT1.3, and SLAH3, might also play a role in the detoxification of ammonium.
