Utilize este identificador para referenciar este registo: http://hdl.handle.net/10400.1/3324
Título: Effects of water deficit on the activity of nitrate reductase and content of sugars, nitrate and free amino acids in the leaves and roots of sunflower and white lupin plants growing under two nutrient supply regimes
Autor: Correia, Maria João
Fonseca, Filomena
Azedo-Silva, João
Dias, Celeste
Barrote, Isabel
Osório, Maria Leonor
Osório, Júlio
Palavras-chave: Water stress
Drought
Nitrate reductase
Helianthus annuus
Lupinus albus
Nutrient supply
Soluble sugar
Free amino acids
Data: 2005
Editora: Wiley
Citação: Correia M. J., Fonseca F., Azedo-Silva J., Dias C., David M., Barrote I., Osório M. L., Osório J. (2005). Effects of water deficit on the activity of nitrate reductase and content of sugars, nitrate and free amino acids in the leaves and roots of sunflower and white lupin plants growing under two nutrient supply regimes. Physiol. Plant., 124: 61-70
Resumo: The effects of soil drying on the activity of nitrate reductase (NR; EC 1.6.6.6) were studied in Helianthus annuus L. and non-nodulated Lupinus albus L. plants growing under two nutrient supply regimes. NR activity was assessed in leaf and root extracts by measuring the activity of the unphosphorylated active form (NRact), the maximal extractable activity (NRmax) and the activation state. To obtain an insight into potential signalling compounds, nitrate, free amino acids and soluble sugars were also quantified. In both species, foliar NRact and NRmax were negatively affected by soil drying and a decreased supply of nutrients, the observed changes in NR activity being linearly correlated with the depletion of nitrate. Similar results were obtained in the roots of sunflower. Conversely, in white lupin roots, NRmax was found to be independent of tissue nitrate concentration. Regardless of the species and organ, the activation state of the enzyme was unaffected by the nutrient supply regime. In well-watered sunflower roots, only about 50% of the existing NR was unphosphorylated, but the activation state increased significantly in response to drought. In contrast, lupin roots always exhibited NR activation state values close to 80%, or even higher. At the leaf level, the NR activation state was hardly changed in response to soil drying. The observed changes in the concentrations of soluble sugars and free amino acids are discussed in terms of their possible contribution to the variations in NR activity.
Peer review: yes
URI: http://hdl.handle.net/10400.1/3324
DOI: http://dx.doi.org/10.1111/j.1399-3054.2005.00486.x
ISSN: 0031-9317
Versão do Editor: http://onlinelibrary.wiley.com/doi/10.1111/j.1399-3054.2005.00486.x/full
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