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KMID : 0903519900330040358
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Journal of the Korean Society of Agricultural Chemistry and Biotechnology
1990 Volume.33 No. 4 p.358 ~ p.358
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Effect of phosphorus deficiency on transport and utilization of nitrogen in nodulated , N2 fixing soybean plants
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Daniel W Israel
Tongmin Sa
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Abstract
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The present study was undertaken to examine the effect of phosphorus deficiency on transport and utilization of fixed nitrogen in soybean plants totally dependent on symbiotic N₂fixation. Phosphorus deficiency decreased ureide-N concentraion in the xylem sap and ureide flux in xylem sap by 50% and 89%, respectively, but the percentage of total nitrogen as ureide-N in the sap was not affected. The total amino acid-N concentration of the sap was 30 and 25 % of the total ureide-N concentration in the xylem sap of control plants and phosphorus deficient plants, respectively. The ureide-N and soluble reduced-N concentrations in leaf and stem tissue were significantly decreased by phosphorus deficiency but those in root tissue were not affected. Ureide-N concentration in nodules and proportion of whole plant ureide in root tissue were higher in phosphorus-deficient plants than in control plants. Sucrose concentration in nodules was reduced by 50 % by phosphorus deficiency, but starch concentration in nodules of phosphorus-deficient plants was significantly higher than in nodules of control plants. Starch comprised more than 75 % of total non-structural carbohydrate in nodules of phosphorus-deficient plants. These results suggested that phosphorus deficiency did not alter the relative allocation of fixed N to the ureide synthesis pathway or the loading of ureides into the xylem. Phosphorus deficiency may have caused restriction of translocation of nitrogenous compounds from nodules and roots to shoots.
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