SEARCH · PubMed Health

Results for “nodulation”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 757 records · Page 42Linked to original sources

PubMed1999

Differential uptake of TI-201 by small-cell lung cancer in a patient with pneumoconiosis-related pulmonary nodules.

A 68-year-old man with pneumoconiosis was thought to have small-cell lung cancer based on the results of a biopsy of a bone tumor. Three pulmonary nodules were observed on a chest radiograph. Compared with a chest radiograph taken 4 months earlier, one of the nodules had grown. It was difficult to differentiate this nodule from pneumoconiosis-related benign pulmonary nodules from the appearance on the chest radiograph and CT. Ga-67 scintigraphy and TI-201 lung SPECT were performed to characterize these nodules. TI-201 SPECT showed differential high uptake in the enlarged nodule, whereas Ga-67 scintigraphy showed equally intense uptake in all these nodules. Transbronchial biopsy of the nodule that showed high TI-201 uptake revealed cancer cell nests against a background of interstitial fibrosis. The pathologic diagnosis was small-cell lung cancer that had developed in lung scar tissue. This case suggests the utility of TI-201 in scintigraphic assessments of pneumoconiosis-related pulmonary nodules when lung cancer is suspected.

Aged↗

PubMedDate not supplied

Subcutaneous nodules at the injection site of low-molecular-weight heparin: a mimic of metastatic disease at CT.

PURPOSE: To describe the appearance and prevalence of subcutaneous nodules in the anterior abdominal wall seen at CT in cancer patients receiving subcutaneous injections of low-molecular-weight heparin (LMWH). METHODS: CT examinations were reviewed in 426 patients receiving subcutaneous abdominal wall injections of LMWH for the presence of nodules. Nodules were evaluated for contour, maximal diameter, CT attenuation, and presence of hazy changes or air in the surrounding fat. RESULTS: Fourteen (3%) of the 426 patients had nodules attributable to subcutaneous injections of LMWH. Findings included poorly defined borders (100%), adjacent hazy soft tissue changes (100%), adjacent air (57%), and a mean CT attenuation of -4.4 HU (range: -50-40 HU). Three (0.7%) of 426 patients had nodules caused by metastatic disease. One (33%) nodule had poorly defined borders, two (67%) had surrounding hazy changes, one (33%) had air in adjacent tissue, and there was a mean CT attenuation of 44 HU (range: 14-140 HU). One (0.2%) patient had a subcutaneous nodule of uncertain etiology. CONCLUSION: Patients receiving subcutaneous injections of LMWH may develop nodules at the injection sites. Such nodules can resemble metastatic tumor deposits at CT, and careful correlation with clinical history and growth trends of metastatic deposits elsewhere in the patient is needed to avoid misdiagnosis.

Abdominal Muscles↗

PubMed1995

Evaluation of thyroid nodules for malignancy using 99Tcm-sestamibi.

99Tcm-sestamibi (99Tcm-MIBI) is used for myocardial perfusion imaging but has also been reported to localize in tumours. The usual thyroid scanning radionuclide is 99Tcm-pertechnetate. Altogether, 161 patients with clinically solitary thyroid nodules had both 99Tcm-MIBI and 99Tcm-pertechnetate thyroid scans, with the nodules being reported as cold, warm or hot. Fine-needle aspiration cytology (FNAC) and surgery were performed in those patients who consented to these procedures. Of 131 patients who had FNAC, only 58 proceeded to surgery. In the surgically treated group, 14 of 58 (24%) were confirmed to have thyroid cancer, whereas 44 of 58 (76%) had benign lesions. The 14 cancerous nodules were cold on the 99Tcm-pertechnetate scan, whereas with 99Tcm-MIBI 11 were warm and 3 were either cold or hot nodules. Of the 44 benign lesions, 18 were cold, 9 were warm and 17 were hot nodules. In those 131 patients who had FNAC, the cytology was reported as benign in 120 of the nodules and malignant in 11. The three false-negative cytologies were reported as follicular adenomas. The benign lesions noted on FNAC and surgery were thyroiditis, adenomas and haemorrhagic or colloid cysts. The results from the 58 surgically treated patients suggest that the warm nodules would need surgery, whereas the cold and hot nodules are unlikely to be malignant. The overall sensitivity of the 99Tcm-MIBI scan was 79% and the specificity 80%, with the warm nodule on 99Tcm-MIBI scan having a positive predictive value of 55% and a negative predictive value of 92%.

Adenocarcinoma, Follicular↗

PubMed2006

Liver transplantation and recurrent hepatocellular carcinoma: predictive value of nodule size in a retrospective and explant study.

BACKGROUND: Recurrence of hepatocellular carcinoma (HCC) after liver transplantation (LT) remains a major cause of post-LT death. METHODS: To assess which preoperative and postoperative variables were related to recurrence of HCC after LT in patients with cirrhosis and HCC, we evaluated 96 patients with cirrhosis (74 with known HCC and 22 with incidental HCC) who survived more than 1 month after LT. RESULTS: The median waiting list time was 36 days (range 1-370 days), and the median interval from detection to transplant was 180 days (range 14-1460 days). The size of largest nodule on imaging was strongly associated with recurrence (odds ratio 1.03; 95% confidence interval 0.99-1.06; P=0.064) when transplantation was performed for known HCC. Among postoperative variables, only the largest nodule diameter (independently of the number of smaller nodules) was multivariately associated with recurrence (odds ratio 1.05; 95% confidence interval 1.01-1.08; P=0.005). The best predictive cutoff was 35 mm in diameter, based on a receiver operating curve with 1-, 3-, and 5-year recurrence-free survival of 90%, 73%, and 49%, respectively, for patients with a nodule 35 mm in diameter or more compared with 96%, 93%, and 89% (P=0.0005), respectively, for patients with smaller nodules. CONCLUSIONS: In our cohort with a short waiting list time, only the largest nodule diameter, especially in the explant, predicted recurrence after LT independently of the number of nodules. New proposals for increasing the diameter of the largest nodule as a selection criteria for LT do not agree with our data, which on the contrary indicate the optimal nodule diameter should be 35 mm or less.

Adult↗

PubMed2002

Genome-wide identification of nodule-specific transcripts in the model legume Medicago truncatula.

The Medicago truncatula expressed sequence tag (EST) database (Gene Index) contains over 140,000 sequences from 30 cDNA libraries. This resource offers the possibility of identifying previously uncharacterized genes and assessing the frequency and tissue specificity of their expression in silico. Because M. truncatula forms symbiotic root nodules, unlike Arabidopsis, this is a particularly important approach in investigating genes specific to nodule development and function in legumes. Our analyses have revealed 340 putative gene products, or tentative consensus sequences (TCs), expressed solely in root nodules. These TCs were represented by two to 379 ESTs. Of these TCs, 3% appear to encode novel proteins, 57% encode proteins with a weak similarity to the GenBank accessions, and 40% encode proteins with strong similarity to the known proteins. Nodule-specific TCs were grouped into nine categories based on the predicted function of their protein products. Besides previously characterized nodulins, other examples of highly abundant nodule-specific transcripts include plantacyanin, agglutinin, embryo-specific protein, and purine permease. Six nodule-specific TCs encode calmodulin-like proteins that possess a unique cleavable transit sequence potentially targeting the protein into the peribacteroid space. Surprisingly, 114 nodule-specific TCs encode small Cys cluster proteins with a cleavable transit peptide. To determine the validity of the in silico analysis, expression of 91 putative nodule-specific TCs was analyzed by macroarray and RNA-blot hybridizations. Nodule-enhanced expression was confirmed experimentally for the TCs composed of five or more ESTs, whereas the results for those TCs containing fewer ESTs were variable.

Agglutinins↗

PubMed2005

Nodulation phenotypes of gibberellin and brassinosteroid mutants of pea.

The initiation and development of legume nodules induced by compatible Rhizobium species requires a complex signal exchange involving both plant and bacterial compounds. Phytohormones have been implicated in this process, although in many cases direct evidence is lacking. Here, we characterize the root and nodulation phenotypes of various mutant lines of pea (Pisum sativum) that display alterations in their phytohormone levels and/or perception. Mutants possessing root systems deficient in gibberellins (GAs) or brassinosteroids (BRs) exhibited a reduction in nodule organogenesis. The question of whether these reductions represent direct or indirect effects of the hormone deficiency is addressed. For example, the application of GA to the roots of a GA-deficient mutant completely restored its number of nodules to that of the wild type. Grafting studies revealed that a wild-type shoot or root also restored the nodule number of a GA-deficient mutant. These findings suggest that GAs are required for nodulation. In contrast, the shoot controlled the number of nodules that formed in graft combinations of a BR-deficient mutant and its wild type. The root levels of auxin and GA were similar among these latter graft combinations. These results suggest that BRs influence a shoot mechanism that controls nodulation and that the root levels of auxin and GA are not part of this process. Interestingly, a strong correlation between nodule and lateral root numbers was observed in all lines assessed, consistent with a possible overlap in the early developmental pathways of the two organs.

Gene Expression Regulation, Plant↗

PubMed2005

Induction of thioredoxin is required for nodule development to reduce reactive oxygen species levels in soybean roots.

Nodules are formed on legume roots as a result of signaling between symbiotic partners and in response to the activities of numerous genes. We cloned fragments of differentially expressed genes in spot-inoculated soybean (Glycine max) roots. Many of the induced clones were similar to known genes related to oxidative stress, such as thioredoxin and beta-carotene hydroxylase. The deduced amino acid sequences of full-length soybean cDNAs for thioredoxin and beta-carotene hydroxylase were similar to those in other species. In situ RNA hybridization revealed that the thioredoxin gene is expressed on the pericycle of 2-d-old nodules and in the infected cells of mature nodules, suggesting that thioredoxin is involved in nodule development. The thioredoxin promoter was found to contain a sequence resembling an antioxidant responsive element. When a thioredoxin mutant of yeast was transformed with the soybean thioredoxin gene it became hydrogen peroxide tolerant. These observations prompted us to measure reactive oxygen species levels. These were decreased by 3- to 5-fold in 7-d-old and 27-d-old nodules, coincident with increases in the expression of thioredoxin and beta-carotene hydroxylase genes. Hydrogen peroxide-producing regions identified with cerium chloride were found in uninoculated roots and 2-d-old nodules, but not in 7-d-old and 27-d-old nodules. RNA interference-mediated repression of the thioredoxin gene severely impaired nodule development. These data indicate that antioxidants such as thioredoxin are essential to lower reactive oxygen species levels during nodule development.

Amino Acid Sequence↗

PubMed2005

Architecture of infection thread networks in developing root nodules induced by the symbiotic bacterium Sinorhizobium meliloti on Medicago truncatula.

During the course of the development of nitrogen-fixing root nodules induced by Sinorhizobium meliloti on the model plant Medicago truncatula, tubules called infection threads are cooperatively constructed to deliver the bacterial symbiont from the root surface to cells in the interior of the root and developing nodule. Three-dimensional reconstructions of infection threads inside M. truncatula nodules showed that the threads formed relatively simple, tree-like networks. Some characteristics of thread networks, such as branch length, branch density, and branch surface-to-volume ratios, were remarkably constant across nodules in different stages of development. The overall direction of growth of the networks changed as nodules developed. In 5-d-old nodules, the overall growth of the network was directed inward toward the root. However, well-defined regions of these young networks displayed an outward growth bias, indicating that they were likely in the process of repolarizing their direction of development in response to the formation of the outward-growing nodule meristem. In 10- and 30-d-old nodules, the branches of the network grew outward toward the meristem and away from the roots on which the nodules developed.

Computer Simulation↗

PubMed1997

Shoot versus Root Signal Involvement in Nodulation and Vegetative Growth in Wild-Type and Hypernodulating Soybean Genotypes.

Grafting studies involving Williams 82 (normally nodulating) and NOD1-3 (hypernodulating) soybean (Glycine max [L.] Merr.) lines and Lablab purpureus were used to evaluate the effect of shoot and root on nodulation control and plant growth. A single- or double-wedge graft technique, with superimposed partial defoliation, was used to separate signal control from a photosynthate supply effect. Grafting of hypernodulated soybean shoots to roots of Williams 82 or L. purpureus resulted in increased nodule numbers. Grafting of two shoots to one root enhanced root growth in both soybean genotypes, whereas the nodule number was a function of shoot genotype but not of the photosynthetic area. In double-shoot, single-root-grafted plants, removing trifoliolate leaves from either Williams 82 or NOD1-3 shoots decreased root and shoot dry matter, attributable to decreased photosynthetic source. Concurrently, Williams 82 shoot defoliation increased the nodule number, whereas NOD1-3 shoot defoliation decreased the nodule number on both soybean and L. purpureus roots. It was concluded that (a) soybean leaves are the dominant site of autoregulatory signal production, which controls the nodule number; (b) soybean and L. purpureus have a common, translocatable, autoregulatory control signal; (c) seedling vegetative growth and nodule number are independently controlled; and (d) two signals, inhibitor and promoter, may be involved in controlling legume nodule numbers.

Journal Article↗

PubMed1978

Nitrogen metabolism of soybeans: I. Effect of tungstate on nitrate utilization, nodulation, and growth.

The effects of N source (6 mm nitrogen as NO(3) (-) or urea) and tungstate (0, 100, 200, 300, and 400 mum Na(2) WO(4)) on nitrate metabolism, nodulation, and growth of soybean (Glycine max [L.] Merr.) plants were evaluated. Nitrate reductase activity and, to a lesser extent, NO(3) (-) content of leaf tissue decreased with the addition of tungstate to the nutrient growth medium. Concomitantly, nodule mass and acetylene reduction activity of NO(3) (-)-grown plants increased with addition of tungstate to the nutrient solution. In contrast, nodule mass and acetylene reduction activity of urea-grown plants decreased with increased nutrient tungstate levels. The acetylene reduction activity of nodulated roots of NO(3) (-)-grown plants was less than 10% of the activity of nodulated roots of urea-grown plants when no tungstate was added. At 300 and 400 mum tungstate levels, acetylene reduction activity of nodulated roots of NO(3) (-)-grown plants exceeded the activity of comparable urea-grown plants.Addition of tungstate to the nutrient solution decreased plant growth, regardless of the N source, although the effect was more pronounced with NO(3) (-) nutrition. The increased nodulation and decreased nitrate reductase activity noted with plants grown in the presence of tungstate and a high (6 mm) external supply of NO(3) (-) suggests that NO(3) (-) does not directly inhibit nodulation but rather affects nodulation indirectly through subsequent metabolism of NO(3) (-).

Journal Article↗

PubMed1980

Carbohydrates in Soybean Nodules: II. DISTRIBUTION OF COMPOUNDS IN SEEDLINGS DURING THE ONSET OF NITROGEN FIXATION.

During the first few days of nitrogen fixation activity by soybean (Glycine max (L.) Merr) root nodules, d-chiro-inositol, myo-inositol, sucrose, alpha,alpha-trehalose, and maltose accumulate rapidly and reach concentrations several fold greater than concentrations in other plant organs. Concentrations of d-pinitol in nodules (>/=1.0 milligrams per gram fresh weight) were similar to concentrations in leaf blades. The concentration of fructose in nodules was lower than concentrations in other plant organs.Comparison of nonnodulated roots, nodulated roots (after removal of nodules), and nodules indicated that nodules may compete successfully with roots for carbohydrates, especially the disaccharides sucrose, alpha,alpha-trehalose, and maltose. Based on the isolation of protoplasts and bacteroids, it was tentatively concluded that the highest concentrations of cyclitols in soybean nodules are located in the infected region and that, inside infected cells, the highest concentrations of d-pinitol and myo-inositol are outside of bacteroids.Evidence for the identification of d-chiro-inositol and maltose in soybean nodules is presented.

Journal Article↗

PubMed1980

Economy of Carbon and Nitrogen in Nodulated and Nonnodulated (NO(3)-grown) Cowpea [Vigna unguiculata (L.) Walp.].

The response of non-nodulated cowpea (Vigna unguiculata (L.) Walp. cv Caloona) to a wide range of NO(3) levels in the rooting medium was studied 40 days after sowing by in vitro assays of plant organs for NO(3) reductase (EC 1.6.6.1) and analyses of root bleeding (xylem) sap for nitrogenous solutes. Plants fed 1, 5, 10, 20, and 40 millimolar NO(3) showed, respectively, 64, 92, 94, and 91% of their total reductase activity in shoots and 34, 30, 66, 62, and 58% of the total N of their xylem sap as NO(3). These data, and the absence in the plants of significant pools of stored NO(3), indicated that shoots were major organs of NO(3) assimilation, especially at levels of NO(3) (10 to 40 millimolar) that maintained plant growth at near maximum rates. Partitioning and utilization of C and N were studied in nodulated, minus NO(3) plants and non-nodulated plants fed 10 or 20 millimolar NO(3), the levels of NO(3) which gave rates of growth and N assimilation closest to those of the symbiotic plants. The conversion of the C of net photosynthate to dry matter was similar in nodulated plants (67%) and NO(3)-grown plants (64%), but greater proportions of photosynthate were translocated to below ground parts of nodulated plants (37%) than of NO(3)-fed plants (23 to 26%). Greater photosynthate consumption by nodulated roots was associated with proportionately greater root growth and respiration and 2-fold greater export of C in xylem than in the NO(3)-fed plants. Theoretical considerations suggest that the elevated CO(2) output of nodulated roots was due not only to CO(2) loss associated with nodule function, but also to a much greater nonassimilatory component of respiration in the supporting root of the nodulated plant compared to roots of the NO(3)-fed plants. Data are compared with previously published information from other legumes.

Journal Article↗

PubMed1983

Reversible dark-induced senescence of soybean root nodules.

Nodule senescence was induced in intact soybean [Glycine max. (L.) Merr., cv Woodworth] plants by an 8-day dark treatment. Dark-induced senescence resulted in the complete loss of acetylene reduction activity, a 67% loss of total soluble protein, and an almost complete loss in total leghemoglobin of nodule extracts. Isoelectric focusing gels demonstrated a preferential loss of certain proteins, which was correlated with an increase in endoprotease specific activity toward azocasein. Nodules were completely green after the 8-day dark treatment. If plants were returned to a normal photoperiod after 8 days in the dark, nodules recovered from the dark treatment in 12 to 16 days. Acetylene reduction activity returned to normal, and both total soluble protein and leghemoglobin were resynthesized while protease activity against azocasein decreased to the level of control nodules. The nodule population that had turned green after 8 days in the dark exhibited a progressive increase in red color starting nearest the exterior of the nodule, and after 16 days of recovery nodules were indistinguishable from control nodules maintained under a normal photoperiod.

Journal Article↗

PubMed1983

Nitrate and Nitrite Reduction in Relation to Nitrogenase Activity in Soybean Nodules and Rhizobium japonicum Bacteroids.

Soybean (Glycine max L. cv Williams) seeds were sown in pots containing a 1:1 perlite-vermiculite mixture and grown under greenhouse conditions. Nodules were initiated with a nitrate reductase expressing strain of Rhizobium japonicum, USDA 110, or with nitrate reductase nonexpressing mutants (NR(-) 108, NR(-) 303) derived from USDA 110. Nodules initiated with either type of strain were normal in appearance and demonstrated nitrogenase activity (acetylene reduction). The in vivo nitrate reductase activity of N(2)-grown nodules initiated with nitrate reductase-negative mutant strains was less than 10% of the activity shown by nodules initiated with the wild-type strain. Regardless of the bacterial strain used for inoculation, the nodule cytosol and the cell-free extracts of the leaves contained both nitrate reductase and nitrite reductase activities. The wild-type bacteroids contained nitrate reductase but not nitrite reductase activity while the bacteroids of strains NR(-) 108 and NR(-) 303 contained neither nitrate reductase nor nitrite reductase activities.Addition of 20 millimolar KNO(3) to bacteroids of the wild-type strain caused a decrease in nitrogenase activity by more than 50%, but the nitrate reductase-negative strains were insensitive to nitrate. The nitrogenase activity of detached nodules initiated with the nitrate reductase-negative mutant strains was less affected by the KNO(3) treatment as compared to the wild-type strain; however, the results were less conclusive than those obtained with the isolated bacteroids.The addition of either KNO(3) or KNO(2) to detached nodules (wild type) suspended in a semisolid agar nutrient medium caused an inhibition of nitrogenase activity of 50% and 65% as compared to the minus N controls, and provided direct evidence for a localized effect of nitrate and nitrite at the nodule level. Addition of 0.1 millimolar sucrose stimulated nitrogenase activity in the presence or absence of nitrate or nitrite. The sucrose treatment also helped to decrease the level of nitrite accumulated within the nodules.

Journal Article↗

PubMed1983

Metabolism of C-labeled photosynthate and distribution of enzymes of glucose metabolism in soybean nodules.

The metabolism of translocated photosynthate by soybean (Glycine max L. Merr.) nodules was investigated by (14)CO(2)-labeling studies and analysis of nodule enzymes. Plants were exposed to (14)CO(2) for 30 minutes, followed by (12)CO(2) for up to 5 hours. The largest amount of radioactivity in nodules was recovered in neutral sugars at all sampling times. The organic acid fraction of the cytosol was labeled rapidly. Although cyclitols and malonate were found in high concentrations in the nodules, they accumulated less than 10% of the radioactivity in the neutral and acidic fractions, respectively. Phosphate esters were found to contain very low levels of total label, which prohibited analysis of the radioactivity in individual compounds. The whole nodule-labeling patterns suggested the utilization of photosynthate for the generation of organic acids (principally malate) and amino acids (principally glutamate).The radioactivity in bacteroids as a percentage of total nodule label increased slightly with time, while the percentage in the cytosol fraction declined. The labeling patterns for the cytosol were essentially the same as whole nodule-labeling patterns, and they suggest a degradation of carbohydrates for the production of organic acids and amino acids. When it was found that most of the radioactivity in bacteroids was in sugars, the enzymes of glucose metabolism were surveyed. Bacteroids from nodules formed by Rhizobium japonicum strain 110 or strain 138 lacked activity for phosphofructokinase and NADP-dependent 6-phosphogluconate dehydrogenase, key enzymes of glycolysis and the oxidative pentose-phosphate pathways. Enzymes of the glycolytic and pentose phosphate pathways were found in the cytosol fraction.In three experiments, bacteroids contained about 10 to 30% of the total radioactivity in nodules 2 to 5 hours after pulse-labeling of plants, and 60 to 65% of the radioactivity in bacteroids was in the neutral sugar fraction at all sampling times. This strongly suggests some absorption and metabolism of sugars by bacteroids in spite of the lack of key enzymes. Bacteroids did possess enzymes for the formation of hexose phosphates from glucose or fructose. Radioactivity in alpha,alpha-trehalose in bacteroids increased until, after 5 hours, trehalose was a major labeled compound in bacteroids. Thus, trehalose synthesis may be a major fate of sugars entering bacteroids.

Journal Article↗

PubMed1984

Rhizobium infection and nodule development in soybean are affected by exposure of the cotyledons to light.

The initiation of Rhizobium infections and the development of nodules on the primary root of soybean Glycine max L. Merr cv Williams seedlings are strongly affected by exposure of the cotyledons/hypocotyls to light. Seedlings in plastic growth pouches were inoculated with R. japonicum in dim light and the position of the root tip of each seedling was marked on the face of the pouch. The pouches were covered and kept in the dark for various times before exposing the upper portions of the plants (cotyledons and hypocotyls) to light. Maximum nodulation occurred if the plants were kept in the dark until 1 day after inoculation. The exposure of plants to light 2 days before inoculation reduced the number of nodules by 50% while the number of nodules was reduced by 70% if the plants were kept in the dark until 7 days after inoculation. Anatomical studies revealed that exposure to light prior to inoculation reduced both the number of infection centers with visible infection threads and the number of infections which developed nodule meristems. Plants kept in the dark for 7 days after inoculation formed a normal number of infection threads above the root tip mark, but very few of these infections developed a nodule meristem. It appears that light stimulates soybean to produce substances which can both inhibit the formation of infection threads and enhance the development of nodules from established infection threads. The effects of light on nodulation appear to be expressed independently of the Rhizobium-induced suppression of nodule formation in younger regions of the root.

Journal Article↗

PubMed1984

Effect of nodulation on assimilate remobilization in soybean.

The objectives of this work were to determine the effect of nodulation on dry matter, reduced-N, and phosphorus accumulation and partitioning in above-ground vegetative parts and pods of field-grown soybean (Glycine max [L.] Merr. cv Harosoy).From comparison of nodulated and nonnodulated isolines, it was estimated that nodulated plants attained 81 and 71% of total-plant (above ground) N from uptake of soil N in 1981 and 1982, respectively. These data, along with visibly greener leaves of nodulated plants, led us to assume that nonnodulated plants were under a moderate N stress relative to nodulated plants. Nonnodulated plants accumulated less total-plant N and partitioned less dry matter and N to the pods, compared with nodulated plants. This occurred even though net photosynthesis, as estimated by rate and amount of dry matter accumulation, was the same for both nonnodulated and nodulated plants. Rate of dry matter and reduced-N accumulation in pods was less for nonnodulated than for nodulated plants while duration of podfill was similar for both isolines. From these data we concluded that moderate N stress affected partitioning of photosynthate rather than net photosynthesis, and that N played a role in translocation of photosynthate to the pods. Total plants (above-ground portion) and pods of both nodulated and nonnodulated plants accumulated similar amounts of phosphorus, which indicated that phosphorus and N accumulation were independent.Remobilization of nitrogen and phosphorus from vegetation to pods preceded dry matter remobilization. It appeared that either more nitrogen accumulation prior to podfill, or continued nitrogen assimilation during podfill would increase nitrogen and dry matter partitioning to pods, but that increasing photosynthesis without concomitantly increasing nitrogen input may not necessarily result in enhanced seed production.

Journal Article↗

PubMed1985

Transport and Partitioning of CO(2) Fixed by Root Nodules of Ureide and Amide Producing Legumes.

Nodulated and denodulated roots of adzuki bean (Vigna angularis), soybean (Glycine max), and alfalfa (Medicago sativa) were exposed to (14)CO(2) to investigate the contribution of nodule CO(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 total radioactivity. When nodules of plants were removed, radioactivity in xylem sap decreased by 90% or more. Pulse-chase experiments indicated that CO(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(2) fixation providing carbon for the assimilation and transport of fixed nitrogen in amide-based legumes. In contrast, CO(2) fixation by nodules of ureide transporting legumes appears to contribute little to assimilation and transport of fixed nitrogen.

Journal Article↗