Synthesis, Storage, and Utilization of Amino Compounds in White Lupin (Lupinus albus L.) 1
AUTOR(ES)
Pate, John S.
RESUMO
Changes in total N and in free amino compounds were followed during growth of nodulated white lupin. Leaflets contained the greatest fraction of plant N but had lower proportions (1 to 4%) of their N in soluble amino form than stem + petioles (10 to 27%) and reproductive parts (15 to 33%). Mobilization of free amino compounds from plant parts to fruits contributed at most only 7% of the total N intake of fruits, compared with 50% in mobilization of other forms of N and 43% from fixation during fruiting. Asparagine was usually the most abundant free amino compound in plant parts, followed by glutamine and alanine. Valine, glycine, isoleucine, aspartic acid and γ-aminobutyric acid comprised the bulk of the remaining soluble amino N. Composition of tissue pools of amino-N closely resembled that of xylem and phloem exudates. Data on N flow and utilization were combined with information on composition of transport fluids to quantify syntheses, exchanges, and consumptions of asparagine, glutamine, aspartic acid, and valine by organs of the 51- to 58-day plant. These amino compounds carried 56, 29, 5, and 2%, respectively, of the N exported from nodules and contributed in roughly commensurate proportions to transport exchanges and N increments of plant parts. There were, however, more than expected involvements of glutamine and valine in mobilization of N from lower leaves, of asparagine in xylem to phloem transfer, and of aspartic acid in cycling of N through the root, and there was a less than expected participation of aspartic acid in xylem to phloem transfer and in phloem translocation to the shoot apex. The significance of these differences is discussed.
ACESSO AO ARTIGO
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=425617Documentos Relacionados
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