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Title: Transport and partitioning of CO/sub 2/ fixed by root nodules of ureide and amide producing legumes. [Vigna angularis; Glycine max; Medicago sativa]

Abstract

Nodulated and denodulated roots of adzuki bean (Vigna angularis), soybean (Glycine max), and alfalfa (Medicago sativa) were exposed to /sup 14/CO/sub 2/ to investigate the contribution of nodule CO/sub 2/ fixation to assimilation and transport of fixed nitrogen. The distribution of radioactivity in xylem sap and partitioning of carbon fixed by nodules to the whole plant were measured. Radioactivity in the xylem sap of nodulated soybean and adzuki bean was located primarily (70 to 87%) in the acid fraction while the basic (amino acid) fraction contained 10 to 22%. In contrast radioactivity in the xylem sap of nodulated alfalfa was primarily in amino acids with about 20% in organic acids. Total ureide concentration was 8.1, 4.7, and 0.0 micromoles per milliliter xylem sap for soybean, adzuki bean, and alfalfa, respectively. While the major nitrogen transport products in soybeans and adzuki beans are ureides, this class of metabolites contained less than 20% of the the total radioactivity. When nodules of plants were removed, radioactivity in xylem sap decreased by 90% or more. Pulse-chase experiments indicated that CO/sub 2/ fixed by nodules was rapidly transported to shoots and incorporated into acid stable constituents. The data are consistent with a role for nodulemore » CO/sub 2/ fixation providing carbon for the assimilation and transport of fixed nitrogen in amide-based legumes. In contrast, CO/sub 2/ fixation by nodules of ureide transporting legumes appears to contribute little to assimilation and transport of fixed nitrogen. 19 references, 2 figures, 5 tables.« less

Authors:
; ; ; ;
Publication Date:
Research Org.:
Univ. of Minnesota, St. Paul
OSTI Identifier:
6830979
Alternate Identifier(s):
OSTI ID: 6830979
Resource Type:
Journal Article
Resource Relation:
Journal Name: Plant Physiol.; (United States); Journal Volume: 78
Country of Publication:
United States
Language:
English
Subject:
59 BASIC BIOLOGICAL SCIENCES; CARBON DIOXIDE; UPTAKE; LEGUMINOSAE; CARBON DIOXIDE FIXATION; PLANT SAP; CHEMICAL COMPOSITION; ALFALFA; BEANS; CARBON 14 COMPOUNDS; EXPERIMENTAL DATA; PHOTOSYNTHESIS; ROOTS; SOYBEANS; TRACER TECHNIQUES; BACTERIA; BIOLOGICAL MATERIALS; CARBON COMPOUNDS; CARBON OXIDES; CHALCOGENIDES; CHEMICAL REACTIONS; DATA; FOOD; INFORMATION; ISOTOPE APPLICATIONS; LABELLED COMPOUNDS; MATERIALS; MICROORGANISMS; NUMERICAL DATA; OXIDES; OXYGEN COMPOUNDS; PHOTOCHEMICAL REACTIONS; PLANTS; RHIZOBIUM; SYNTHESIS; VEGETABLES 550501* -- Metabolism-- Tracer Techniques

Citation Formats

Vance, C.P., Boylan, K.L.M., Maxwell, C.A., Heichel, G.H., and Hardman, L.L.. Transport and partitioning of CO/sub 2/ fixed by root nodules of ureide and amide producing legumes. [Vigna angularis; Glycine max; Medicago sativa]. United States: N. p., 1985. Web.
Vance, C.P., Boylan, K.L.M., Maxwell, C.A., Heichel, G.H., & Hardman, L.L.. Transport and partitioning of CO/sub 2/ fixed by root nodules of ureide and amide producing legumes. [Vigna angularis; Glycine max; Medicago sativa]. United States.
Vance, C.P., Boylan, K.L.M., Maxwell, C.A., Heichel, G.H., and Hardman, L.L.. Tue . "Transport and partitioning of CO/sub 2/ fixed by root nodules of ureide and amide producing legumes. [Vigna angularis; Glycine max; Medicago sativa]". United States. doi:.
@article{osti_6830979,
title = {Transport and partitioning of CO/sub 2/ fixed by root nodules of ureide and amide producing legumes. [Vigna angularis; Glycine max; Medicago sativa]},
author = {Vance, C.P. and Boylan, K.L.M. and Maxwell, C.A. and Heichel, G.H. and Hardman, L.L.},
abstractNote = {Nodulated and denodulated roots of adzuki bean (Vigna angularis), soybean (Glycine max), and alfalfa (Medicago sativa) were exposed to /sup 14/CO/sub 2/ to investigate the contribution of nodule CO/sub 2/ fixation to assimilation and transport of fixed nitrogen. The distribution of radioactivity in xylem sap and partitioning of carbon fixed by nodules to the whole plant were measured. Radioactivity in the xylem sap of nodulated soybean and adzuki bean was located primarily (70 to 87%) in the acid fraction while the basic (amino acid) fraction contained 10 to 22%. In contrast radioactivity in the xylem sap of nodulated alfalfa was primarily in amino acids with about 20% in organic acids. Total ureide concentration was 8.1, 4.7, and 0.0 micromoles per milliliter xylem sap for soybean, adzuki bean, and alfalfa, respectively. While the major nitrogen transport products in soybeans and adzuki beans are ureides, this class of metabolites contained less than 20% of the the total radioactivity. When nodules of plants were removed, radioactivity in xylem sap decreased by 90% or more. Pulse-chase experiments indicated that CO/sub 2/ fixed by nodules was rapidly transported to shoots and incorporated into acid stable constituents. The data are consistent with a role for nodule CO/sub 2/ fixation providing carbon for the assimilation and transport of fixed nitrogen in amide-based legumes. In contrast, CO/sub 2/ fixation by nodules of ureide transporting legumes appears to contribute little to assimilation and transport of fixed nitrogen. 19 references, 2 figures, 5 tables.},
doi = {},
journal = {Plant Physiol.; (United States)},
number = ,
volume = 78,
place = {United States},
year = {Tue Jan 01 00:00:00 EST 1985},
month = {Tue Jan 01 00:00:00 EST 1985}
}
  • The dependence of alfalfa (Medicago sativa L.) root and nodule nonphotosynthetic CO/sub 2/ fixation on the supply of currently produced photosynthate and nodule nitrogenase activity was examined a various times after phloem-girdling and exposure of nodules to Ar:O/sub 2/. Phloem-girdling was effected 20 hours and exposure to Ar:O/sub 2/ was effected 2 to 3 hours before initiation of experiments. Nodule and root CO/sub 2/ fixation rates of phloem-girdled plants were reduced to 38 and 50%, respectively, of those of control plants. Exposure to Ar:O/sub 2/ decreased nodule CO/sub 2/ fixation rates to 45%, respiration rates to 55%, and nitrogenase activitiesmore » to 51% of those of the controls. The products of nodule CO/sub 2/ fixation were exported through the xylem to the shoot mainly as amino acids within 30 to 60 minutes after exposure to /sup 14/CO/sub 2/. In contrast to nodules, roots exported very little radioactivity, and most of the /sup 14/C was exported as organic acids. The nonphotosynthetic CO/sub 2/ fixation rate of roots and nodules averaged 26% of the gross respiration rate, i.e. the sum of net respiration and nonphotosynthetic CO/sub 2/ assimilation. Nodules fixed CO/sub 2/ at a rate 5.6 times that of roots, but since nodules comprised a small portion of root system mass, roots accounted for 76% of the nodulated roots system CO/sub 2/ fixation. The results indicate that nodule CO/sub 2/ fixation in alfalfa is associated with N assimilation.« less
  • The effects of water stress and CO/sub 2/ enrichment on photosynthesis, assimilate export, and sucrose-P synthase activity were examined in the field grown soybean plants. In general, leaves of plants grown in CO/sub 2/-enriched atmospheres (300 microliters per liter above unenriched control, which was 349 +/- 12 microliters per liter between 0500 and 1900 hours EST over the entire season) had higher carbon exchange rates (CER) compared to plants grown at ambient CO/sub 2/, but similar rates of export and similar activities of sucrose-P synthase. On most sample dates, essentially all of the extra carbon fixed as a result ofmore » CO/sub 2/ enrichment was partitioned into starch. CO/sub 2/-enriched plants had lower transpiration rates and therefore had a higher water use efficiency (milligrams CO/sub 2/ fixed per gram H/sub 2/O transpired) per unit leaf area compared to nonenriched plants. Water stress reduced CER in nonenriched plants to a greater extent than in CO/sub 2/-enriched plants. As CER declined, stomatal resistance increased, but this was not the primary cause of the decrease in assimilation because internal CO/sub 2/ concentration remained relatively constant. Export of assimilates was less affected by water stress than was CER. When CERs were low as a result of the imposed stress, export was supported by mobilization of reserves (mainly starch). Export rate and leaf sucrose concentration were related in a curvilinear manner. When sucrose concentration was above about 12 milligrams per square decimeter, obtained with nonstressed plants at high CO/sub 2/, there was no significant increase in export rate. Assimilate export rate was also correlated positively with SPS activity and the quantitative relationship varied with CER. Thus, export rate was a function of both CER and carbon partitioning. 28 references, 11 figures.« less
  • The acidity of ambient rainfall and its effect on soil and plants is a growing concern. Glass microelectrodes were used to investigate the effect of soil pH and foliar application of acid rain on the rhizosphere pH of alfalfa (Medicago sativa L. cv. Arrow), corn (Zea mays L. cv. B72 {times} MO17), and soybean (Glycine max (L.) Merr. cv. Williams 82). Plant roots were grown in minirhizotrons containing a reformed sample of Seymour silt loam A horizon over a silty clay loam Bt horizon. Low and high pH levels of 4.9 and 6.2 in the A horizon and 4.0 andmore » 5.7 in the Bt horizon were established using dilute sulfuric acid or calcium ozide, respectively. Palnts received daily applications of simulated rain, which was either acid (pH 3.1) or non-acid (pH 5.6). After 5,6, or 15 d of foliar applications to corn, soybean, or alfalfa, respectively, the rhizosphere pH was measured using a glass microelectrode. The pH values for corn and soybean increased with distance from the root while the pH values for alfalfa decreased with distance. As the soil pH increased from 4 to near 6, the difference between the pH at the root surface and the bulk soil increased from 0 to near 1. A trend for lateral root pH values at all distances to be slightly higher than main roots was observed. Increasing the pH of the A horizon had no significant effect on the rhizospehre pH of corn roots growing in the Bt horizon, but significantly increased soybean rhizosphere pH in the Bt horizon. Acid rain applications caused foliar damage, and tended to decrease rhizosphere pH, but few effects were significant.« less
  • Roots of alfalfa (Medicago sativa L.), white clover (Trifolium repens L.), and soybean (Glycine max (L.) Merr.) seedlings are frequently contaminated with bacteria even after surface sterilization of the seeds and germination under aspetic conditions. Several seed-sterilization procedures were compared for their ability to minimize or eliminate such contamination without damaging the plant. Mercuric chloride proved the best seed disinfectant for alfalfa and white clover. Calcium hypochlorite was the best for soybean. For alfalfa seeds, treatment with 95% ethanol (v/v) for 60 min followed by 0.2% HgCl{sub 2} (v/v) for 15 min prior to rinsing and imbibition resulted in amore » low frequency (< 5%) of seed and root contamination. This treatment resulted in no measurable damage to alfalfa seedlings with respect to root growth, nodulation efficiency, or rate of nodule emergence following inoculation with Rhizobium meliloti. Longer exposures to HgCl{sub 2} further reduced bacterial contamination, but also caused modest reductions in seed germination. None of the surface-sterilization techniques tested completely eliminated bacterial contaminants. It appears that these sterilization-resistant contaminants are borne within the seed and proliferate on plant surfaces after germination, with possible effects on plant health.« less
  • The objectives of this study were to determine if nonphotosynthetic CO/sub 2/ fixation by root nodules contributes carbon for the assimilation of fixed N/sub 2/ in alfalfa (Medicago sativa L.) and birdsfoot trefoil (Lotus corniculatus L.) and if assimilation products are partitioned to different plant organs. Effective alfalfa nodules excised from or attached to roots had apparent /sup 14/CO/sub 2/ fixation rates of 50 to 80 ..mu..g CO/sub 2/ kg/sup -1/s/sup -1/ (dry weight) at 0.0012 to 0.0038 mole fraction CO/sub 2/. Nodule CO/sub 2/ fixation rates increased six- to seven-fold as ambient CO/sub 2/ was raised from 0.0038 tomore » 0.0663 mole fraction. Respiration rates of nodules (3 to 4 mg CO/sub 2/ kg/sup -1/s/sup -1/) were 10 to 100-fold higher than /sup 14/CO/sub 2/ fixation rates of nodules. Pulse chase experiments with /sup 14/CO/sub 2/ combined with nodule and xylem sap analysis demonstrated the initial products of root and nodule CO/sub 2/ fixation were organic acids. However, the export of fixed /sup 14/C from effective nodules was primarily in the form of amino acids. In contrast, nodule and/or root fixed /sup 14/C in ineffectively nodulated alfalfa and denodulated effective alfalfa and birdsfoot trefoil was transported primarily as organic acids. Aspartate, asparagine, alanine, glutamate, and glutamine were the most heavily labeled compounds in the amino acid fraction of both effective alfalfa and birdsfoot trefoil nodules exposed to /sup 14/CO/sub 2/. By contrast, asparate, asparagine, and glutamine were the predominantly labeled amino acids in xylem sap collected from nodulated effective roots exposed to /sup 14/CO/sub 2/. The occurrence of nodule CO/sub 2/ fixation in alfalfa and birdsfoot trefoil and the export of fixed carbon as asparagine and aspartate to roots and shoots is consistent with a role for CO/sub 2/ fixation by nodules in providing carbon skeletons for assimilation and transport of symbiotically fixed N/sub 2/.« less