ISSN:
1573-5036
Keywords:
amino acids
;
15N
;
phloem sap
;
Prunus dulcis
;
urea
Source:
Springer Online Journal Archives 1860-2000
Topics:
Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
Notes:
Abstract Two treatments were employed to influence the amount of amino nitrogen (N) transport in phloem. In walnut trees (Juglans regia L.), developing fruit significantly reduced the efflux of foliar-applied 15N-enriched urea from treated spurs over a 33-day period in comparison with similarly-treated defruited spurs. Those data suggest that local aboveground demand for N influences vascular transport of amino N. In another experiment, a 1% urea solution was applied foliarly to 5-year old `Mission' almond trees [Prunus dulcis (Mill.) D. A. Webb] to increase the concentration of amino N in the phloem. The effect of foliar N treatments on a) the transport and distribution of labelled urea N within the trees over the experimental period and b) the uptake of soil-applied labelled N were determined by replicated whole tree excavation, fractionation into various tree components and mass spectrometric analyses of the 14N/15N ratios. Concentrations and composition of amino acids in the phloem and xylem saps of control trees and trees receiving foliar-applied urea were also determined. In foliar urea-treated trees, the amino acid concentrations increased significantly in leaf and bark phloem exudate, within 24 and 96 h, respectively. Foliar-applied urea N was translocated to the roots of almond trees over the experimental period and decreased soil N uptake. The results of these experiments are consistent with the hypothesis that aboveground N demand affects the amount of amino N cycling between shoots and roots, and may be involved in the regulation of soil N uptake.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1023/A:1026572615441
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