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At least 19 recordsLinked to original sources

PubMed2006

Phytoextraction of cadmium by rice (Oryza sativa L.), soybean (Glycine max (L.) Merr.), and maize (Zea mays L.).

Selecting a phytoextraction plant with high Cd-accumulating ability based on the plant's compatibility with mechanized cultivation techniques may yield more immediately practical results than selection based on high tolerance to Cd. Rice (Oryza sativa L., cv. Nipponbare and Milyang 23), soybean (Glycine max [L.] Merr., cv. Enrei and Suzuyutaka), and maize (Zea mays L., cv. Gold Dent) were grown on one Andosol and two Fluvisols with low concentration of Cd contamination ranging from 0.83 to 4.29 mg Cd kg(-1), during 60 days in pots (550 mL) placed in a greenhouse. Shoot Cd uptake was as follows: Gold Dent<Enrei and Nipponbare<Suzuyutaka and Milyang 23. Several soil Cd fractions after Milyang 23 harvesting decreased most. Milyang 23 accumulated 10-15% of the total soil Cd in its shoot. The Milyang 23 rice is thus promising for phytoextraction of Cd from paddy soils with low contamination level.

Aerobiosis↗

PubMed1988

Haloxyfop Inhibition of the Pyruvate and the alpha-Ketoglutarate Dehydrogenase Complexes of Corn (Zea mays L.) and Soybean (Glycine max [L.] Merr.).

The grass-specific herbicide haloxyfop, ((+/-)-2-[4-((3-chloro-5-(trifluoromethyl)-2-pyridinyl)oxy)-phenoxy] propionic acid) has been shown to inhibit lipid synthesis and respiration, to cause the accumulation of amino acids, and not to affect cellular sugar or ATP levels. Thus studies were carried out with enzyme activities from corn (Zea mays L.) (haloxyfop sensitive) and soybean (Glycine max [L.] Merr.) (haloxyfop tolerant) to locate the possible inhibition sites among the glycolytic and tricarboxylic acid (TCA) cycle enzymes. Following along the oxidative metabolism pathway of sugars, the pyruvate dehydrogenase complex (PDC) was the first enzyme among the glycolytic enzymes that demonstrated noticeable inhibition by 1 millimolar haloxyfop. Kinetic studies with corn and soybean PDC from both purified etioplasts and mitochondria gave K(i) values of from 1 to 10 millimolar. Haloxyfop also inhibited the activity of the TCA cycle enzyme, the alpha-ketoglutarate dehydrogenase complex (alpha-KGDC) which carries out the same reaction as PDC except for the substitution of alpha-ketoglutarate for pyruvate as one of the substrates. The K(i) values were somewhat lower in this case (near 1 millimolar). The relatively high K(i) values for both enzyme complexes would indicate that these may not be the herbicidal sites of inhibition, but it is possible that the herbicide could be concentrated in compartments and/or the substrate concentrations may be well below optimal. Likewise little difference was seen in the haloxyfop inhibition of the enzyme activities from the sensitive species, corn, and from the tolerant species, soybean, so the selectivity of the herbicide is not evident from these results. The inhibition of the PDC and alpha-KGDC as the mode of action of haloxyfop is, however, consistent with the observed physiological effects of the herbicide, and these are the only enzymic activities so far found to be sensitive to haloxyfop.

Journal Article↗

PubMed2004

A comparative study of the role of the major proteinases of germinated common bean (Phaseolus vulgaris L.) and soybean (Glycine max (L.) Merrill) seeds in the degradation of their storage proteins.

Two types of cysteine proteases, low-specificity enzymes from the papain family and Asn-specific from the legumain family are generally considered to be the major endopeptidases responsible for the degradation of seed storage proteins during early seedling growth. The action of the corresponding enzymes (CPPh1 and LLP, respectively) from common bean (Phaseolus vulgaris L.) on phaseolin (the common bean storage protein), and on the homologous soybean (Glycine max (L.) Merrill) storage protein, beta-conglycinin, was studied. Under the action of LLP, proteolysis of phaseolin was limited to cleavage of its interdomain linker. No cleavage of the interdomain linker occurred in beta-conglycinin with LLP. LLP action was restricted to splitting off the disordered N-terminal extensions of alpha and alpha' subunits. No extensive hydrolysis (degradation to short TCA-soluble peptides) of either protein occurred under the action of LLP. CPPh1 cleaved the phaseolin subunits into roughly half-sized fragments at the onset of proteolysis. The cleavage was accompanied by a small (8-10%) decrease of protein. No decrease of protein occurred with further incubation. Thus the two most active proteinases detected in common bean seedlings individually were incapable of the extensive degradation of phaseolin. Extensive hydrolysis of phaseolin was only achieved by the consecutive action of LLP and CPPh1. Similar cleavages occurred during the action of CPPh1 on beta-conglycinin. However, by contrast with phaseolin, CPPh1 by itself accomplished the extensive hydrolysis of beta-conglycinin. The differences in the course of proteolysis of the proteins studied were determined by their structural peculiarities.

Amino Acid Sequence↗

PubMed2002

NolX of Sinorhizobium fredii USDA257, a type III-secreted protein involved in host range determination, Iis localized in the infection threads of cowpea (Vigna unguiculata [L.] Walp) and soybean (Glycine max [L.] Merr.) nodules.

Sinorhizobium fredii USDA257 forms nitrogen-fixing nodules on soybean (Glycine max [L.] Merr.) in a cultivar-specific manner. This strain forms nodules on primitive soybean cultivars but fails to nodulate agronomically improved North American cultivars. Soybean cultivar specificity is regulated by the nolXWBTUV locus, which encodes part of a type III secretion system (TTSS). NolX, a soybean cultivar specificity protein, is secreted by TTSS and shows homology to HrpF of the plant pathogen Xanthomonas campestris pv. vesicatoria. It is not known whether NolX functions at the bacterium-plant interface or acts inside the host cell. Antibodies raised against S. fredii USDA257 NolX were used in immunocytochemical studies to investigate the subcellular localization of this protein. Immunostaining of paraffin-embedded sections of developing soybean and cowpea (Vigna unguiculata [L.] Walp) nodules revealed localization of NolX in the infection threads. Protein A-gold immunocytochemical localization studies utilizing affinity-purified NolX antibodies revealed specific deposition of gold particles in the fibrillar material inside infection threads. Similar immunogold localization studies failed to detect NolX in thin sections of mature soybean and cowpea nodules. The results from this study indicate that NolX is expressed in planta only during the early stages of nodule development.

Bacterial Proteins↗

PubMed1982

De Novo Purine Synthesis in Nitrogen-Fixing Nodules of Cowpea (Vigna unguiculata [L.] Walp.) and Soybean (Glycine max [L.] Merr.).

Partially purified, cell-free extracts from nodules of cowpea (Vigna unguiculata L. Walp. cv. Caloona) and soybean (Glycine max L. Merr. cv. Bragg) showed high rates of de novo purine nucleotide and purine base synthesis. Activity increased with rates of nitrogen fixation and ureide export during development of cowpea plants; maximum rates (equivalent to 1.2 micromoles N(2) per hour per gram fresh nodule) being similar to those of maximum nitrogen fixation (1-2 micromoles N(2) per hour per gram fresh nodule). Extracts from actively fixing nodules of a symbiosis not producing ureides, Lupinus albus L. cv. Ultra, showed rates of de novo purine synthesis 0.1% to 0.5% those of cowpea and soybean. Most (70-90%) of the activity was associated with the particulate components of the nodule, but up to 50% was released from this fraction by osmotic shock. The accumulated end products with particulate fractions were inosine monophosphate and aminoimidazole carboxamide ribonucleotide. Further metabolism to purine bases and ureides was restricted to the soluble fraction of the nodule extract. High rates of inosine monophosphate synthesis were supported by glutamine as amide donor, lower rates (10-20%) by ammonia, and negligible rates with asparagine as substrate.

Journal Article↗

PubMed1989

Genetic variation in an inbred plant: variation in tissue cultures of soybean [Glycine max (L.) Merrill].

Although soybean [Glycine max (L.) Merrill] grows as an inbreeding, generally homozygous, plant, the germplasm of the species contains large amounts of genetic variation. Analysis of soybean DNA has indicated that variation of RFLP (restriction fragment length polymorphism) markers within the species usually entails only two alleles at any one locus and that mixtures of such dimorphic loci account for virtually all of the restriction fragment variation seen in soybean (G. max), and in its ancestors, G. soja and G. gracilis. We report here that tissue cultures prepared from root tissue of individual soybean plants develop RFLP allelic differences at various loci. However, these newly generated alleles are almost always the same as ones previously found and characterized in other varieties of cultivated soybean (cultivars). This repeated generation of particular alleles suggests that much of the genetic variation seen in soybean could be the consequence of specific, relatively frequently employed, recombinational events. Such a mechanism would allow inbred cultivars to generate genetic variation (in the form of alternative alleles) in a controlled manner, perhaps in response to stress.

DNA Probes↗

PubMed1983

Characterization of Solute Efflux from Dehydration Injured Soybean (Glycine max L. Merr) Seeds.

Soybean (Glycine max L. Merr) seeds lose their tolerance of dehydration between 6 and 36 hours of imbibition. Soybean axes and cotyledons were excised 6 hours (tolerant of dehydration) and 36 hours (susceptible) after commencing imbibition and subsequently dehydrated to 10% moisture. Kinetics of the efflux of potassium, phosphate, amino acid, sugar, protein, and total electrolytes were compared in the four treatments during rehydration. Only slight differences were observed in the kinetics of solute efflux between the two cotyledon treatments dehydrated at 6 and 36 hours suggesting that the cotyledons may retain their tolerance of dehydration at this stage of germination. Several symptoms of injury were observed in the axes dehydrated at 36 hours. An increase in the initial leakage of solutes during rehydration, as quantified by the y-intercept of the linear regression line for solute efflux between 2 and 8 hours suggests an increased incidence of cell rupture. An increase in the rate of solute efflux (slope of regression line between 2 and 8 hours) from fully rehydrated axes was observed in comparison to axes dehydrated at 6 hours. The Arrhenius activation energy for potassium, phosphate, and amino acid efflux decreased and for protein remained unchanged. Both observations indicate an increase in membrane permeability in dehydration-injured tissue. Increasing the H(+) concentration of the external solution increased K(+) efflux from both control and dehydrated/rehydrated samples, increased sugar efflux from axes at 6 hours imbibition but decreased sugar efflux from axes at 36 hours imbibition, indicating changes in membrane properties during germination. The dehydration treatment did not alter the pattern of the pH response of axes dehydrated at 6 or 36 hours but did increase the quantity of potassium and sugar efflux from dehydration injured axes. These results are interpreted as indicating that dehydration of soybean axes at 36 hours of imbibition increased both the incidence of cell rupture during rehydration and altered membrane permeability of the rehydrated tissue.

Journal Article↗

PubMed1994

Detoxification of Formaldehyde by the Spider Plant (Chlorophytum comosum L.) and by Soybean (Glycine max L.) Cell-Suspension Cultures.

The phytotoxicity of formaldehyde for spider plants (Chlorophytum comosum L.), tobacco plants (Nicotiana tabacum L. cv Bel B and Bel W3), and soybean (Glycine max L.) cell-suspension cultures was found to be low enough to allow metabolic studies. Spider plant shoots were exposed to 7.1 [mu]L L-1 (8.5 mg m-3) gaseous [14C]-formaldehyde over 24 h. Approximately 88% of the recovered radioactivity was plant associated and was found to be incorporated into organic acids, amino acids, free sugars, and lipids as well as cell-wall components. Similar results were obtained upon feeding [14C]formaldehyde from aqueous solution to aseptic soybean cell-suspension cultures. Serine and phosphatidylcholine were identified as major metabolic products. Spider plant enzyme extracts contained two NAS+-dependent formaldehyde dehydrogenase activities with molecular mass values of about 129 and 79 kD. Only the latter enzyme activity required glutathione as an obligatory second cofactor. It had an apparent Km value of 30 [mu]M for formaldehyde and an isoelectric point at pH 5.4. Total cell-free dehydrogenase activity corresponded to 13 [mu]g formaldehyde oxidized h-1 g-1 leaf fresh weight. Glutathione-dependent formaldehyde dehydrogenases were also isolated from shoots and leaves of Equisetum telmateia and from cell-suspension cultures of wheat (Triticum aestivum L.) and maize (Zea mays L.). The results obtained are consistent with the concept of indoor air decontamination with common room plants such as the spider plant. Formaldehyde appears to be efficiently detoxified by oxidation and subsequent C1 metabolism.

Journal Article↗

PubMed1982

Identification and Quantitative Analysis of Indole-3-Acetyl-l-Aspartate from Seeds of Glycine max L.

Indole-3-acetyl-l-aspartate (IAAsp) was isolated from seeds of Glycine max L. cv. Hark and its identity established by its chromatographic performance and its mass spectral fragmentation. Following acid hydrolysis, the aspartate moiety was shown to be the l-enantiomer by reverse phase high performance liquid chromatographic retention time of the bisethyl ester derivatized with 2,3,4,6-tetra-O-acetyl-beta-d-glycopyranosyl isothiocyanate. Isotope dilution analysis using [(14)C]IAAsp as internal standard showed that soybean seed contained 10 mumol/kg IAAsp and this accounted for one-half of the total indoleacetic acid of the seed.

Journal Article↗

PubMed1981

Enzymic synthesis of lignin precursors. Comparison of cinnamoyl-CoA reductase and cinnamyl alcohol:NADP+ dehydrogenase from spruce (Picea abies L.) and soybean (Glycine max L.).

Cambial sap of spruce (Picea abies) proved to be a good source for isolation of cinnamoyl-CoA reductase and cinnamyl alcohol:NADP+ dehydrogenase. Apparently homogeneous enzymes were obtained by a multistep procedure including dye-ligand chromatography and for the reductase also affinity chromatography on (coenzyme A)-agarose. An improved purification procedure for the reductase from soybean cell cultures is also reported. Molecular weights and subunit composition of reductase and dehydrogenase from spruce are very similar to those of the corresponding enzymes from soybean. Reduction of feruloyl-CoA to coniferaldehyde catalysed by the reductase is a freely reversible reaction with an equilibrium constant of 5.6 x 10(-4) M at pH 6.25. A strong dependence of the Michaelis constants on the type of buffer was found. For reductase the Km-value of feruloyl-CoA in phosphate buffer (5.2 microM) is about 14-times similar than in citrate buffer (73 microM). Pronounced differences in substrate specificities between the enzymes from spruce and soybean were found, which reflect the different lignin composition of gymnosperms and dicotyledenous angiosperms. From the kinetic constants of the enzymes it can be concluded that under physiological conditions feruloyl-CoA is the preferred substrate for the reductase from both sources whereas sinapoyl-CoA is a substrate only for the soybean reductase and sinapyldehyde a substrate only for the soybean dehydrogenase. 4-Coumaroyl-CoA is a poor substrate for the reductase from both spruce and soybean. This result is consistent with the low content of 4-coumaryl alcohol units in gymnosperm and angiosperm lignin.

Alcohol Oxidoreductases↗

PubMed1993

Subcellular Localization of Oxygen Defense Enzymes in Soybean (Glycine max [L.] Merr.) Root Nodules.

Soybean (Glycine max [L.] Merr.) root nodules contain the enzymes of the ascorbate-glutathione pathway to minimize oxidative damage. In the present study, fractionation and immunocytochemistry were used to determine the subcellular location of the enzymes of this pathway. All four enzymes (ascorbate peroxidase, monodehydroascorbate reductase, dehydroascorbate reductase, and glutathione reductase) were present in the soluble fraction from nodule plant cells and in isolated mitochondria. No activity was detected in peroxisomes. Bacteroids contained glutathione reductase but not the other enzymes of this pathway. Immunogold localization indicated that ascorbate peroxidase was present in the cytosol of infected and uninfected cells but not in the peribacteroid space. Results of immunogold and immunofluorescence studies indicated that monodehydroascorbate reductase was located primarily in the cell wall, suggesting that ascorbate regeneration in the cytoplasm may proceed primarily through the action of dehydroascorbate reductase. The possible roles of monodehydroascorbate reductase in cell wall metabolism are discussed.

Journal Article↗

PubMed1985

Use of N-Bromoacetyl-l-ornithine to Study l-Ornithine and l-Arginine Biosynthesis in Soybean (Glycine max L.) Cell Cultures.

The effect of the inhibitor N(2)-bromoacetyl-l-ornithine (NBAO) on the biosynthesis of ornithine in higher plants, was investigated using soybean cells (Glycine max L. var Mandarin), grown in suspension culture. The NBAO was found to reduce the specific activity of the enzyme N(2)-acetyl-l-ornithine: l-glutamate N-acetyltransferase (EC 2.3.1.35). In contrast, the specific activity of the enzyme acetyl coenzyme A:L-glutamate N-acetyltransferase (EC 2.3.1.1), which is also involved in N-acetylglutamate biosynthesis, was not significantly changed. Estimation of the concentrations of free amino acids in the soluble fraction of the cells showed that while ornithine levels were decreased, glutamic acid levels were increased in the presence of NBAO. While arginine levels initially increased in the presence of NBAO, they finally decreased near the end of the growth period. Evidence was obtained that the initial increase in arginine levels was due to the inhibition of arginase (EC 3.5.3.1) by N(2)-bromoacetyl l-ornithine. We conclude that the reaction catalyzed by N(2)-acetyl-l-ornithine:l-glutamate N-acetyl transferase is a rate limiting reaction in vivo.

Journal Article↗

PubMed1988

Translocation of Sulfate in Soybean (Glycine max L. Merr).

Sulfate translocation in soybean (Glycine max L. Merr) was investigated. More than 90% of the sulfate entering the shoot system was recoverable in one or two developing trifoliate leaves. In young plants, the first trifoliate leaf contained between 10 to 20 times as much sulfate as the primary leaves, even though both types of leaf had similar rates of transpiration and photosynthesis. We conclude that most of the sulfate entering mature leaves is rapidly loaded into the phloem and translocated to sinks elsewhere in the plant. This loading was inhibited by carbonylcyanide m-chlorophenylhydrazone and selenate. At sulfate concentrations below 0.1 millimolar, more than 95% of the sulfate entering primary leaves was exported. At higher concentrations the rate of export increased but so did the amount of sulfate remaining in the leaves. Removal of the first trifoliate leaf increased two-fold the transport of sulfate to the apex, indicating that these are competing sinks for sulfate translocated from the primary leaves. The small amount of sulfate transported into the mesophyll cells of primary leaves is a result of feedback regulation by the intracellular sulfate pool, not a consequence of their metabolic inactivity. For example, treatment of plants with 2 millimolar aminotriazole caused a 700 nanomoles per gram fresh weight increase in the glutathione content of primary leaves, but had no effect on sulfate aquisition.

Journal Article↗

PubMed1983

l-Arginine and l-Canavanine Metabolism in Jack Bean, Canavalia ensiformis (L.) DC. and Soybean, Glycine max (L.) Merr.

Studies have been conducted with the arginase (l-arginine amidinohydrolase, EC 3.5.3.1) of two legumes: jack bean, Canavalia ensiformis (L.) DC., a l-canavanine-containing plant and soybean, Glycine max, a canavanine-free species. Analyses of the arginase obtained from gradient-purified mitochondria of these legumes revealed that the arginine-dependent (ADA) and canavanine-dependent activities (CDA) were localized within this organelle.Kinetic analyses of affinity-purified mitochondrial arginase revealed an apparent K(m) of 7 to 8 millimolar for arginine with both the jack bean and soybean arginases. Comparable determinations with canavanine revealed an apparent K(m) of 38 millimolar with the jack bean enzyme; the affinity for this arginine analog with the soybean enzyme is so poor that product formation remained linear even with a canavanine concentration of 890 millimolar.A single macromolecule appears to be responsible for both the ADA and CDA of jack bean arginase. Ion-exchange chromatography of mitochondrial arginase revealed that the ADA and CDA eluted as a single, discrete peak from DEAE-cellulose. Analyses with arginine- and canavanine-linked Sepharose failed to reveal more than one enzyme. Both the ADA and CDA increased by nearly identical amounts following elution from arginine- and canavanine-linked cyanogen bromide-activated sepharose. Neither ADA nor CDA increased preferentially over the other.

Journal Article↗

PubMed1991

Induced plant responses to pathogen attack. Analysis and heterologous expression of the key enzyme in the biosynthesis of phytoalexins in soybean (Glycine max L. Merr. cv. Harosoy 63).

In soybean (Glycine max L.), pathogen attack induces the formation of glyceollin-type phytoalexins. The biosynthetic key enzyme is a reductase which synthesizes 4,2', 4'-trihydroxychalcone in co-action with chalcone synthase. Screening of a soybean cDNA library from elicitor-induced RNA in lambda gt11 yielded two classes of reductase-specific clones. The deduced proteins match to 100% and 95%, respectively, with 229 amino acids sequenced in the purified plant protein. Four clones of class A were expressed in Escherichia coli, and the proteins were tested for enzyme activity in extracts supplemented with chalcone synthase. All were active in 4,2',4'-trihydroxychalcone formation, and the quantification showed that shorter lengths of the cDNAs at the 5' end correlated with progressively decreasing enzyme activities. Genomic blots with DNA from plants capable of 4,2',4'-trihydroxychalcone synthesis revealed related sequences in bean (Phaseolus vulgaris L.) and peanut (Arachis hypogaea L.), but not in pea (Pisum sativum L.). No hybridization was observed with parsley (Petroselinum crispum) and carrot (Daucus carota) which synthesize other phytoalexins. The reductase protein contains a leucine-zipper motif and reveals a marked similarity with other oxidoreductases most of which are involved in carbohydrate metabolism.

Acyltransferases↗

PubMed2006

LDL-antioxidant pterocarpans from roots of Glycine max (L.) Merr.

The methanolic root extract of Glycine max (L.) Merr. was chromatographed, which yielded 10 flavonoids, including three isoflavones 1-3, five pterocarpans 4-8, one flavonol 9, and one anthocyanidin 10. All isolated compounds were examined for LDL-antioxidant activities using four different assay systems on the basis of Cu2+-mediated oxidation. Among them, seven compounds showed potent LDL-antioxidant activities in the thiobarbituric acid reactive substances (TBARS) assay, the lag time of conjugated diene formation, relative electrophoretic mobility (REM), and fragmentation of apoB-100 on copper-mediated LDL oxidation. Three pterocarpans 4, 6, and 7, never reported as LDL-antioxidant, showed potent activities with IC50 values of 19.8, 0.9, 45.0 microM, respectively, in comparison with probucol (IC50 = 5.6 microM) as positive control. Interestingly, coumestrol 6 (IC50 = 0.9 microM) showed 20 times more activity in the TBARS assay than genistein (IC50 = 30.1 microM) and daidzein (IC50 = 21.6 microM), representative antioxidants in soybean. Moreover, coumestrol 6 had an extended lag time of 190 min at 3.0 microM in measuring conjugated diene formation, while both genistein (120 min) and daidzein (93 min) lag times were extended to less than 120 min at the same concentration.

Copper↗

PubMed2005

[Identification of drought tolerant germplasm and inheritance and QTL mapping of related root traits in soybean (Glycine max (L.) Merr.)].

Fifty nine accessions of soybean (Glycine max (L.) Merr.) selected from 301 ones in Huang-Huai-Hai and Middle-Lower Changjiang Valleys were tested in two years for their tolerance to drought by using the mean membership index value averaged over those of plant height,leave number,dry root weight and dry stem and leaf weight. Four most tolerant accessions (Rank 1) and two most sensitive ones (Rank 5) were identified. There existed very significant correlations between drought tolerance and relative values of dry root weight,total root length, and root volume (per plant dry weight basis), respectively,which could be used as root indicators of drought tolerance. The RIL population derived from Kefeng 1 x Nannong 1138-2 was used to analyze the inheritance of the three related root traits by using the segregation analysis of quantitative traits under the major gene plus polygene mixed inheritance model. The results showed that between the two parents (Rank 1 x Rank 4), the relative values of dry root weight,total root length and root volume were respectively controlled by two major genes (linked together for the latter two traits, recombination value being 4.30% and 1.93%, respectively) plus polygenes with their major gene heritability values of 62.26%-91.81% and polygene heritability values 2.99%-24.75%, indicating that the major genes,especially the one with larger effect,accounted for a major part of the genetic variation between the two parents. It was identified that five, three, and five QTLs located on N6-C2, N8-D1b + W, N11-E, and N18-K linkage groups for relative dry root weight, total root length and root volume, respectively. Each of the traits appeared to have one locus (Dw1, R/1, and Rv1) with relatively large effect in comparison with their other loci, and those major ones were located near the same site of the same linkage group N6-C2. The results of segregation analysis and QTL mapping appeared pretty consistent with each other, which could be used as a demonstration of each other.

Adaptation, Physiological↗

PubMed1972

Canopy and Seasonal Profiles of Nitrate Reductase in Soybeans (Glycine max L. Merr.).

Nitrate reductase activity of soybeans (Glycine max L. Merr.) was evaluated in soil plots and outdoor hydroponic gravel culture systems throughout the growing season. Nitrate reductase profiles within the plant canopy were also established. Mean activity per gram fresh weight per hour of the entire plant canopy was highest in the seedling stage while total activity (activity per gram fresh weight per hour times the total leaf weight) reached a maximum when plants were in the full bloom to midpod fill stage. Nitrate reductase activity per gram fresh weight per hour was highest in the uppermost leaf just prior to full expansion and declined with leaf position lower in the canopy. Total nitrate reductase activity per leaf was also highest in the upper-most fully expanded leaf during early growth stages. Maximum total activity shifted to leaf positions lower in the plant canopy with later growth stages.Nitrate reductase activity of soybeans grown in hydroponic systems was significantly higher than activity of adjacent soil grown plants at later growth stages, which suggested that under normal field conditions the potential for nitrate utilization may not be realized. Nitrate reductase activity per gram fresh weight per hour and nitrate content were positively correlated over the growing season with plants grown in either soil or solution culture. Computations based upon the nitrate reductase assay of plants grown in hydroponics indicated that from 1.7 to 1.8 grams N could have been supplied to the plant via the nitrate reductase process. The harvested seed contained 1.1 to 1.2 grams N per plant. Thus, based on previous estimates of approximately 32% of the final N distribution being in the vegetative plant parts, the estimated input of reduced nitrogen via the enzyme assay was in agreement with the actual N accumulation.The amount of calculated N(2)-fixation by nodules per season with plants grown in hydroponics was less than 2% of the computed nitrate reduced via leaf nitrate reductase. Thus, the level of nitrate in the nutrient solution appeared to be quite inhibitory to N(2)-fixation.

Journal Article↗