Effect of nitrogen supply on nitrogen metabolism in the citrus cultivar ‘Huangguogan’

Abstract

Nitrogen metabolism in citrus has received increased attention due to its effects on plant growth and productivity. However, little is known about the effects of nitrogen fertilization on nitrogen metabolism in young trees of citrus cultivar ‘Huangguogan’ (Citrus reticulata × Citrus sinensis). Here, genes encoding nitrate reductase (NR), nitrite reductase (NiR), glutamine synthetase (GS), glutamate dehydrogenase (GDH), and asparagine synthetase (AS), represented as HgNR, HgNiR, HgGS, HgGDH, and HgAS, respectively, were cloned from Huangguogan. Deduced protein sequences were analyzed and proteins were confirmed to be localized in their respective cellular organelles. Moreover, pot-cultured ‘Huangguogan’ seedlings were fertilized with 0 (N1), 1.36 (N2), 1.81 (N3), 2.26 (N4), or 2.72 (N5) kg N/year, for 12 months. Enzyme activity and enzyme-gene expression were studied in roots, leaves, and fruits at different stages. Finally, the effects of N application rate on root activity, leaf N, soluble protein, yield, and fruit quality at the ripening stage were measured. The results showed that: 1) HgNR, HgNiR, HgGDH, and HgAS gene products were found mainly in the cytoplasm and plasma membrane, while HgGS gene product was found mainly in cytoplasm and mitochondria. 2) Gene expression and enzyme activity differed among plant organs. As the root is in permanent direct contact with the soil we suggest that root gene expression and enzyme activity can be used as reference to determine N application rate. 3) Yield, fruit quality, enzyme activity, and enzyme-related gene expression were considerably lower at low than at high-N supply. However, they were all inhibited by excess nitrogen (i.e., 2.72 kg/year). Therefore, we recommend 1.81 kg N/year as the optimal N application rate for young ‘Huangguogan’ trees.

Suprimento de nitrogênio, estado nutricional, produção e qualidade da borracha de árvores de Hevea brasiliensis

“…O efeito detrimental observado para a fertilização excessiva com N sobre a performance produtiva da seringueira estaria associado, ao menos em parte, ao estresse nutricional causado diretamente pela concentração elevada de N no tecido foliar e subsequentes danos ao metabolismo das folhas (Marschner, 1995;Liao Tabela 2. Concentração de nutrientes em folhas de árvores de Hevea brasiliensis com 12 anos, em função da aplicação de N. Table 2.…”

Hydrogen sulfide and rhizobia synergistically regulate nitrogen (N) assimilation and remobilization during N deficiency‐induced senescence in soybean

“…In contrast, the gene expression and protein level of NR in roots were decreased by the interaction of H 2 S and rhizobia, ultimately causing a reduction in NR functional activity. Similarly, N fertilizer application increased the transcriptional level and enzyme activity of NR in roots by 220.0% and 5.0%, respectively, and that in leaves by 51.5% and 13.8%, respectively (Liao et al, ). In addition, it is possible that the activity or molecular regulation of different N metabolic enzymes differed in shoots and roots under salt stress (Teh, Shaharuddin, Ho, & Mahmood, ).…”

Enhancement of nitrogen use efficiency through agronomic and molecular based approaches in cotton

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