Production of zearalenone,T-2 toxin,and deoxynivalenol by Fusarium spp. isolated from plant materials grown in North Carolina

Fusarium spp. isolated from plant materials grown in the hot, humid climate of North Carolina were tested for production of mycotoxins. Isolates of F. acuminatum, F. graminearum, F. moniliforme, F. oxysporum, and F. solani produced zearalenone while isolates of F. equiseti and F. graminearum produced T-2 toxin and deoxynivalenol, respectively. This is the first report of zearalenone production by F. solani. The toxins were identified by capillary gas chromatography-mass spectrometry. These findings suggest that there are toxigenic strains of Fusarium indigenous to the warmer regions of the USA and that fasariotoxicoses of animals in this region are not necessarily the result of importing toxic grains from the cooler, upper midwestern USA.Paper No. 8953 of the Journal Series of North Carolina Agricultural Research Service, Raleigh, North Carolina. The use of trade names in this publication does not imply endorsement by the North Carolina Agricultural Research Service of the product named nor criticism of similar ones not mentioned.     

Physiological characteristics and competitive ability of plasmid-cured derivatives of Rhizobium fredii USDA 206

Rhizobium fredii USDA 206 carries four plasmids which total more than 1200 MDa of DNA. A series of plasmid-cured mutants of strain USDA 206 were derived and compared to determine possible functions of the plasmids, as well as the effect of the plasmids on growth and competitiveness of their host strains. No functions of plasmid pRj206a or pRj206c were found. Plasmid pRj206b was found to have a higher copy number in the non-mucoid (Muc^–) derivative strain 206CANS. Transfer of pRj206b conferred on two recipient strains a Muc^– phenotype indicating control of exopolysaccharide synthesis by this plasmid. The same plasmid appeared to encode repression of melanin synthesis. Strain 206CANS was also shown to have a shorter generation time than USDA 206 and to out-compete USDA 206 in batch and chemostat culture. Competition for nodulation indicated little difference between USDA 206 and 206CANS, while USDA 206 appeared to be more competitive than two of the other cured derivatives.Paper no. 11886 of the Journal Series of North Carolina Agricultural Research Service, Raleigh, NC 27695-7643. Cooperative investigations of the U.S. Department of Agricultural, Agricultural Research Service and the North Carolina Agricultural Research Service Raleigh, NC 27695-7601, USA     

Jasmonic acid-dependent increases in the level of specific polypeptides in soybean suspension cultures and seedlings

Adding 2–30 M jasmonic acid (JA) to photomixotrophic suspension cultures of soybean increased the level of several soluble polypeptides isolated by SDS-PAGE. The major polypeptides affected by JA treatment were at M_r 31,200 (p31) and M_r 39,000. Spraying leaves of soybean seedlings with 10–50 M JA also increased the level of several soluble polypeptides including p31. The use of Con A affinity chromatography demonstrated that p31 was a glycoprotein and that JA increased the level of three other glycoproteins at M_r 22,000, 33,000, and 52,000. The JA treatment did not alter the growth or morphology of the seedlings. JA at 2–30 M did not significantly inhibit the growth of the cultured cells and did not significantly alter the chlorophyll concentration. However, JA at concentrations above 30 M inhibited growth and chlorophyll levels in cultured cells. The suspension cultured cells could provide a reliable bioassay for jasmonic acid.This paper represents cooperative investigations of the U.S. Department of Agriculture, Agricultural Research Service, and the North Carolina Agricultural Research Service, Raleigh, North Carolina 27695-7601. Paper No. 10997 of the journal series of the North Carolina Agricultural Research Service, Raleigh, NC 27695-7601.Mention of a trademark or proprietary product does not constitute a guarantee or warranty of the product by the U.S. Department of Agriculture or the North Carolina Agricultural Research Service and does not imply its approval to the exclusion of other products that may also be suitable.     

Substrate specificity in hydrocarbon utilizing microorganisms

Three bacteria (designated stram JOB5, 7E4, and 7E1C) isolated from soil by elective culture techniques and capable of growth on a wide variety of hydrocarbons were tested for substrate specificity. Non-proliferating cells of strain JOB5 grown on each of the C₁ to C_N series of normal ahphatic hydrocarbons were assayed for the capacity to oxidize all the alkanes, alcohols, fatty acids, and methyl-ketones in the homologous series of straight chain compounds. Cells of strain 7E4 grown on the gaseous alkanes (C₁ C₄) and strain 7E1C grown on propane were tested for the ability to oxidize the C₁ to C₄ n-alkanes, alcohols, and fatty acids.Contribution from Microbiology, North Carolina Agricultural Experiment Station, Raleigh, North Carolina Published with the approval of the Director of Research as paper No 2395 of the Journal Series.Part of this work was done while the author was associated with the late Dr. Jackson W. Foster, at the University of Texas, Austin.     

Jasmonic acid-dependent increase in vegetative storage protein in soybean tissue cultures

Adding jasmonic acid (JA) to autotrophic, photomixotrophic, or heterotrophic suspension cultures of soybean specifically increased the level of the M_r 30,000 subunit of soybean vegetative storage protein (VSP-30) and a polypeptide at M_r 18,000 that interacted with antibody raised against VSP. Using photomixotrophic cells, the increase was observed at concentrations as low as 10 nM JA and the increase was evident within 2 h following treatment. Below 10 M, JA did not inhibit growth of the cells but did cause browning at higher concentrations. Other plant growth regulators, including abscisic acid (ABA), gibberellic acid, and benzyl adenine, did not alter the level of VSP-30 either in the presence or absence of JA. Methyl jasmonate (JA-Me), 3-oxo-2-butyl-cyclopentane-1-acetate, and 3-oxo-2-pentyl-cyclopentane-1-acetate also increased VSP-30 but at higher concentrations than JA. Altering the level of reduced nitrogen or sucrose in the medium did not alter VSP-30 levels in the cells, but at higher sucrose concentrations, sensitivity to JA was reduced. The dramatic increase in VSP-30 elicited by JA appears to be a specific response to the phytohormone.Cooperative investigations of the United States Department of Agriculture, Agricultural Research Service, and the North Carolina Agricultural Research Service, Raleigh, NC 27695-7643. Paper No. 12474 of the Journal Series of the North Carolina Agricultural Research Service, Raleigh, NC 27695-7643.Mention of a trademark or proprietary product does not constitute a guarantee or warranty of the product by the United States Department of Agriculture or the North Carolina Agricultural Research Service and does not imply its approval to the exclusion of other products that may also be suitable.     

Effects of pH and other factors on the phosphate dependence of photosynthesis in spinach chloroplasts

Chloroplast stromal volume and pH influenced the phosphate (Pi)-dependence of photosynthesis of spinach (Spinacia oleracea L.) chloroplasts. Decreasing the sorbitol concentration in the reaction mixture from 0.35 to 0.25 M, or decreasing the external pH from 8.3 to 7.3, extended the induction period of photosynthesis and decreased both the optimal [Pi] and the minimal [Pi] required to inhibit O₂ evolution completely. At least part of the effect of external pH was attributable to changes in stromal pH on the basis of effects of NH₄Cl and sodium acetate at a constant external pH. When the external pH was increased from 7.3 to 8.3, the stromal pH changed only about 0.6 pH units. Hence, the pH gradient across the envelope was diminished and the efflux of phosphoglycerate relative to dihydroxyacetone phosphate was enhanced.Calvin-cycle activity, varied with light intesity or electron transport inhibitors, affected the rate of photosynthesis but not the induction period or the Pi optimum for photosynthesis. Relatively low Calvin-cycle activity was apparently sufficient to fill metabolite pools and thus terminate the induction period. The results indicate that pH does not affect the Pi dependence of photosynthesis by reducing Calvin-cycle activity. Rather, it is postulated that at low stromal pH, larger metabolic pools are required to maintain maximum rates of photosynthesis because of changes in substrate affinity of some Calvin-cycle enzymes. Consequently, chloroplast photosynthesis would be more sensitive to exogenous Pi.Abbreviations DHAP dihydroxyacetone phosphate - PGA 3-phosphoglycerate - Pi inorganic phosphate Cooperative investigations of the North Carolina Agricultural Research Service and Agricultural Research, Science and Education Administration, U.S. Department of Agriculture, Raleigh, N.C. Paper No. 6391 of the Journal Series of the North Carolina Agricultural Research Service, Raleigh, N.C., USA     

Biosynthesis of superoxide dismutase and catalase in chemostat culture of Saccharomyces cerevisiae

Summary The effects of oxygen (100%), paraquat (0.5 mM), and copper (0.1 mM) on the growth and the biosynthesis of the antioxidant enzymes, superoxide dismutase (SOD) and catalase, were studied in Saccharomyces cerevisiae grown in glucose-limited chemostat cultures. The effect of dilution rates (D, h⁻¹) on cell mass, glucose consumption, ethanol production, oxygen uptake, and specific activities of SOD and catalase were also investigated at each steady state. SOD was optimally produced at D-values between 0.22 and 0.26 h⁻¹ in the presence of oxygen or paraquat, and at D-values greater than 0.17 h⁻¹ when copper was used. On the other hand, catalase activity decreased with increasing D-values. However, the presence of copper or 100% oxygen repressed catalase activity at low D-values (D<0.1 h⁻¹), and decreased the rate of oxygen uptake at all D-values tested. The presence of paraquat affected the rate of oxygen uptake only at high D-values (D>0.22 h⁻¹). We also studied the effect of oxygen concentration on the biosynthesis of SOD and catalase at D=0.1 h⁻¹. The data clearly show that synthesis of SOD and catalase, though correlated with changes in oxygen tension, are independent of one another. Paper Number 10871 of the Journal Series of North Carolina Agricultural Research Service, Raleigh, NC 27 695. The use of trade names in this publication does not imply endorsement by the North Carolina Agricultural Research Service of the products named, nor criticism of similar ones not mentioned     

Linkage relationships of biochemical markers to Q- and C-band variants in a large black kindred

Summary Lod scores are reported for 86 biochemical to cytogenetic marker comparisons in a Black kindred. Analysis with unconfirmed locus assignments resulted in 12 exclusions of close linkage.This paper is based on a thesis submitted by the senior author in partial fulfillment of the Ph.D. degree at North Carolina State University, Raleigh.Research supported by the National Heart and Lung Institute Grant HLO-3341, National Institute of Mental Health Grant MH 26621, and National Institute of General Medical Sciences Grant GN 16697; paper number 6281 of the Journal Series of the North Carolina Agricultural Research Service, Raleigh, North Carolina.     

Isolation and partial characterization of Fix− mutants from Rhizobium strain 32H1

Summary Eight ineffective mutant strains were isolated from N-methyl-N'-nitro-N-nitrosoguanidine mutagenized cultures of cowpea Rhizobium strain 32H1. Strains CR1, CR2, CR3, CR4, CR5 and CR6 induced more, but smaller, nodules than the wild type. With the exception of strain CR2, these mutant strains reduced less than 1% of the amount of acetylene reduced by the wild type, in both the free-living and symbiotic assays. Strain CR2 reduced acetylene in the free-living assay but not in the symbiotic assay. Strains CR7 and CR8 responded variably (5–20% of the wild type) in free-living and symbiotic acetylene reduction assays. Nodules also varied from small white to normal-sized pink nodules. The phenotypic characteristics of the mutant strains were consistant with all leguminous plants tested and were stable upon reisolation from nodules. Fully effective revertants were selected from 4 of the ineffective mutant strains by the use of the leguminous plant,Macroptilium lathyroides. Serology, patterns of resistance to anti-bacterial agents, phage-typing, and antibiotic resistance markers were used to confirm strain identification.Cooperative investigations of the United States Department of Agriculture, Agricultural Research Service and the North Carolina Agricultural Research Service, Raleigh, North Carolina. Paper no. 8834 of the Journal Series of the North Carolina Agricultural Research Service at Raleigh.     

Order of the ilv genes of Salmonella montevideo

Summary Ilv mutants of aSalmonella typhimurium-Salmonella montevideo hybrid were used in cotransduction studies to obtain evidence for the order of theilv genes ofS. montevideo. The following order, which is the same as that previously reported forS. typhimurium, is derived:ilvE-ilvD-ilvA-ilvC.From the Departments of Genetics and Biochemistry, School of Agriculture and Life Sciences, and School of Physical and Mathematical Sciences, North Carolina State University, Raleigh, North Carolina 27607. Paper No. 3300 of the Journal Series of the North Carolina State University Agricultural Experiment Station, Raleigh, North Carolina. Supported by Research Grant GM 14184-04 from the Public Health Service.     

Resolution of two molecular forms of sucrose-phosphate synthase from maize,soybean and spinach leaves

Two forms of sucrose-phosphate synthase (EC 2.4.1.14) were resolved from leaves of three species, maize (Zea mays L. cv. Pioneer 3184), soybean (Glycine max (L.) Merr., cv. Ransom) and spinach (Spinacia oleracea L. cv. Resistoflay) by hydroxyapatite Ultrogel chromatography, using a 75-mM (designated peak 1) and 250-mM (peak 2) K-phosphate discontinuous-gradient elution. Rechromatography of the two forms showed that they were not readily interconvertible. The distribution of activity between the two forms differed among species and changed during purification of the enzyme. Recovery of peak-1 activity was specifically lowered when maize leaf extracts were prepared in the absence of magnesium, indicating that the two forms may differ in stability. In addition, the forms of the enzyme from maize differed in the extent of glucose-6-phosphate activation. These results provide evidence for the existence of multiple forms of sucrose-phosphate synthase in leaves of different species and that the forms differ in regulatory properties.Abbreviations Fru6P fructose 6-phosphate - Glc6P glucose 6-phosphate - HAU hydroxyapatite Ultrogel - Pi inorganic phosphate - SPS sucrose-phosphate synthase - UDP uridine 5-diphosphate - UDPG uridinediphosphate glucose Cooperative investigations of the United States Department of Agriculture, Agricultural Research Service, and the North Carolina Agricultural Research Service, Raleigh. Paper No. 10511 of the Journal Series of the North Carolina Agricultural Research Service, Raleigh. Supported in part by USDA Competitive Research Grant No. 85-CRCR-1-1568     

Selection for components related to body composition in mice: direct responses

Summary Replicated within full-sib family single-trait selection was conducted for 10 generations in mice for (1) high or low 12-week epididymal fat pad percentage (100 x epididymal fat pad weight/body weight) or (2) high or low 12-week hind carcass percentage (100 x hind carcass weight/body weight). Pooled realized heritabilities based on high, low and divergent selection were 0.66±0.09, 0.65±0.13 and 0.66±0.05 for epididymal fat pad percentage and 0.48±0.08, 0.33±0.08 and 0.40±0.04 for hind carcass percentage. The pooled realized genetic correlation (r_{G R}) between epididymal fat pad percentage and hind carcass percentage based on divergence was –0.67±0.04. Other estimates of (r_{G R}) were: epididymal fat pad percentage with body weight (0.57±0.05); epididymal fat pad percentage with epididymal fat pad weight (1.17±0.05); hind carcass percentage with body weight (–0.61±0.09); hind carcass percentage with hind carcass weight (–0.05±0.11). Indirect measures of fat and lean tissue percentages were highly heritable, and (r_{G R}) between them would be desirable from the standpoint of analogous types of traits in livestock. In the same context, undesirable (r_{G R})'s were found between epididymal fat pad percentage and body weight and between hind carcass percentage and body weight.Paper No. 10957 of the Journal Series of the North Carolina Agricultural Research Service, Raleigh, North Carolina 27695-7601, USA. The use of trade names in this publication does not imply endorsement by the North Carolina Agricultural Research Service of the products named, nor criticism of similar ones not mentioned     

Transformation of Acetobacter polyoxogenes with Plasmid DNA by Electroporation

Acetobacter polyoxogenes was transformed with plasmid DNA by electroporation. The following points were essential for transformation: (i) dilution of the culture broth with cold water and air bubbling of the culture broth for transformation at discharging from a jar fermentor, and (ii) selection of transformants by liquid cultivation. For shortening of the lag time in cultivation for selection of transformants, the following treatments were useful: (i) addition of sucrose to the cell suspension during transformation and to the broth for cultivation, and (ii) addition of 1 mm MgCl₂ to a mixture of cells and DNA during electroporation.     

Genetically defined peptidases of maize I. Biochemical characterization of allelic and nonallelic forms

A number of biochemical properties have been investigated for both allelic and nonallelic forms of maize peptidases. Four aminopeptidases exist in maize (LAP-A, LAP-B, LAP-C, and LAP-D) and are the products of four diallelic loci. The aminopeptidases fall into two biochemical groups on the basis of these studies. LAP-A and LAP-D have comparatively low apparent K _m (K _app) values for arginine-naphthylamide derivatives and high velocities for arginine-naphthylamide and lysine-naphthylamide. LAP-B and LAP-C, on the other hand, have lower K _app values for leucine-naphthylamide and higher velocities for nonpolar amino acid-naphthylamides than for arginine-naphthylamide. LAP-A and LAP-D are also relatively more heat stable than LAP-B and LAP-C and have somewhat higher molecular weights (71,500) than LAP-B and LAP-C (63,500). In determining molecular weights of the peptidases, use was made of their differential substrate specificities toward amino acid-naphthylamides. Some properties of genetically defined maize endopeptidase are also presented. Maize endopeptidase is inhibited by the sulfhydryl reagents N-ethylmaleimide and p-chloromercuribenzoate (pCMB), and by tosyl lysine chloromethyl ketone. Maize aminopeptidase activity is inhibited by N-ethylmaleimide, pCMB, and EDTA (ethylenediamine tetraacetic acid).This research was supported by U.S. Atomic Energy Commission Contract AT(38-1)-770, and in part by Grant No. GM-22733 from the National Institute of General Medical Sciences, U.S. Public Health Service, to J. G. S.Paper No. 4740 of the Journal Series of the North Carolina Agricultural Experiment Station, Raleigh, North Carolina.     

Oxygen-Poor Microzones as Potential Sites of Microbial N2 Fixation in Nitrogen-Depleted Aerobic Marine Waters

The nitrogen-deficient coastal waters of North Carolina contain suspended bacteria potentially able to fix N₂. Bioassays aimed at identifying environmental factors controlling the development and proliferation of N₂ fixation showed that dissolved organic carbon (as simple sugars and sugar alcohols) and particulate organic carbon (derived from Spartina alterniflora) additions elicited and enhanced N₂ fixation (nitrogenase activity) in these waters. Nitrogenase activity occurred in samples containing flocculent, mucilage-covered bacterial aggregates. Cyanobacterium-bacterium aggregates also revealed N₂ fixation. In all cases bacterial N₂ fixation occurred in association with surficial microenvironments or microzones. Since nitrogenase is oxygen labile, we hypothesized that the aggregates themselves protected their constituent microbes from O₂. Microelectrode O₂ profiles revealed that aggregates had lower internal O₂ tensions than surrounding waters. Tetrazolium salt (2,3,5-triphenyl-3-tetrazolium chloride) reduction revealed that patchy zones existed both within microbes and extracellularly in the mucilage surrounding microbes where free O₂ was excluded. Triphenyltetrazolium chloride reduction also strongly inhibited nitrogenase activity. These findings suggest that N₂ fixation is mediated by the availability of the appropriate types of reduced microzones. Organic carbon enrichment appears to serve as an energy and structural source for aggregate formation, both of which were required for eliciting N₂ fixation responses of these waters.     

THE EFFECTS OF OXYGEN,CARBON DIOXIDE,AND PRESSURE ON GROWTH IN CHILOMONAS PARAMECIUM AND TETRAHYMENA GELEII FURGASON

1. The effects of O₂, CO₂, and pressure were studied in two very different species of protozoa, a flagellate, Chilomonas paramecium, grown in acetate-ammonium solution and a ciliate, Tetrahymena geleii, grown in 2 per cent proteose-peptone solution. 2. Chilomonas and Tetrahymena live and reproduce in solutions exposed to a wide range of O₂ concentrations, but Chilomonas is killed at high O₂ tensions in which Tetrahymena grows best. The optimum O₂ concentration for Chilomonas is about 75 mm. pressure but it lives and reproduces in O₂ tensions as low as 0.5 mm. while Tetrahymena fails to grow in concentrations below 10 mm. O₂ pressure. 3. With a constant O₂ tension of 50 mm. pressure, it was found that there is no significant variation in growth in Chilomonas between 50 mm. and 740 mm. total pressure. In Tetrahymena, however, under the same conditions, an optimum total pressure was found at about 500 mm. and growth is comparatively poor at 50 mm. total pressure. 4. Tetrahymena does not live very long in CO₂ tensions over 122 mm., although Chilomonas grows as well at 400 mm. CO₂ as in air at atmospheric pressure (0.2 mm. CO₂). Tetrahymena grows best in an environment minus CO₂, but the optimum for Chilomonas is 100 mm. CO₂ at which pressure an average of 668,600 ± 30,000 organisms per ml. was produced (temperature, 25 ± 1° C.). 5. Chilomonads grown in high CO₂ concentrations (e.g., 122 mm.) produce larger starch granules and more starch than those grown in ordinary air at atmospheric pressure. 6. In solutions exposed to 75 mm. O₂ tension (optimum) and 122 mm. CO₂ plus 540 mm. N₂ pressure, chilomonads contain very little, if any, fat. This phenomenon seems to be due to the action of CO₂ on the mechanisms concerned with fat production. 7. In Tetrahymena exposed to pure O₂, there is very little fat compared to those grown in atmospheric air. This may be due to the greater oxidation of fat in the higher O₂ concentrations. 8. Further evidence is presented in support of the contention that Chilomonas utilizes CO₂ in the production of starch.     

Nitrogen Fixation and Hydrogen Metabolism in Relation to the Dissolved Oxygen Tension in Chemostat Cultures of the Wild Type and a Hydrogenase-Negative Mutant of Azorhizobium caulinodans

Both the wild type and an isogenic hydrogenase-negative mutant of Azorhizobium caulinodans growing ex planta on N₂ as the N source were studied in succinate-limited steady-state chemostat cultures under 0.2 to 3.0% dissolved O₂ tension. Production or consumption of O₂, H₂, and CO₂ was measured with an on-line-connected mass spectrometer. In the range of 0.2 to 3.0%, growth of both the wild type and the mutant was equally dependent on the dissolved O₂ tension: the growth yield decreased, and the specific O₂ consumption and CO₂ production increased. A similar dependency on the dissolved O₂ tension was found for the mutant with 2.5% H₂ in the influent gas. The H₂/N₂ ratio (moles of H₂ evolved per mole of N₂ consumed via nitrogenase) of the mutant, growing with or without 2.5% H₂, increased with increasing dissolved O₂ tensions. This increase in the H₂/N₂ ratio was small but significant. The dependencies of the ATP/N₂ ratio (moles of ATP consumed per mole of N₂ fixed) and the ATP/2e^- ratio [moles of ATP consumed per mole of electron pairs transferred from NAD(P)H to nitrogenase] on the dissolved O₂ tension were estimated. These dependencies were interpreted in terms of the physiological concepts of respiratory protection and autoprotection.     

Rhizobium meliloti distribution in the soil following alfalfa inoculation

Summary Alfalfa seeds, inoculated with an antibiotic-resistantRhizobium meliloti strain, were planted in three replicated field plots at Clayton, N.C. Core samples were taken three times in the next year at 0, 10, and 20 cm from the edge of each plot. Soil subsamples were taken from within each core sample at 0, 6, 12, and 18 cm depths. The numbers of the inoculum Rhizobium strain in each soil subsample were determined by inoculation of alfalfa plants with diluted soil samples. In general the distribution of rhizobia showed some movement outward and downward in the soil. Lower counts were obtained at the surface during summer. The Rhizobium persistence pattern in the soil differed in the three plots which is consistent with the variability in Rhizobium numbers often observed in established alfalfa stands. Cooperative investigation of the United States Department of Agriculture, Science and Education Administration, Agricultural Research and the North Carolina Agricultural Research Service, Raleigh, North Carolina. Paper No. 6818 of the Journal Series of the North Carolina Agricultural Research Service at Raleigh.     

Regulation of sucrose-phosphate-synthase activity in spinach leaves by protein level and covalent modification

A dot-blot technique was developed using monoclonal antibodies to measure, rapidly and accurately, the amount of sucrose-phosphate synthase (SPS; EC 2.4.1.14) protein present in a crude extract from spinach (Spinacia oleracea L. cv. Dark Green Bloomsdale) leaves; this was compared with SPS activity in this material. During leaf development, increased SPS activity followed closely the increase in enzyme-protein level, indicating denovo synthesis or altered turn-over rates for SPS. In contrast, activation of SPS by illumination of leaves or by mannose treatment of leaf discs in the dark (M. Stitt et al. Planta 174, 217–230) occurred without a significant change in the level of enzyme protein. Since conditions which altered SPS activity did not affect immunoprecipitation or mobility of the 120-kilodalton (kDa) subunit of the enzyme during denaturing gel electrophoresis, some form of protein modification other than proteolysis must be involved. Overall, the results indicate that regulation of SPS activity can involve changes in the level of enzyme protein and-or covalent modification.Abbreviations kDa kilodalton - SDS-PAGE sodium dodecylsulfate polyacrylamide gel electrophoresis - SPS sucrosephosphate synthase Cooperative investigations of the U.S. Department of Agriculture, Agricultural Research Service, and the North Carolina Agricultural Reseach Service, Raleigh. Paper No. 11789 of the Journal Series of the North Carolina Agricultural Research Service, Raleigh, NC 27695-7643, USA     

The influence of temperature and nitrate on vegetative growth and nitrogen accumulation by nodulated soybeans

Summary Inoculated soybeans [Glycine max (L.) Merrill] were grown in controlled environments to evaluate the relationship between temperature and applied NO₃−N on growth rates, N accumulation, and acetylene reduction activity during the vegetative growth stage. Soybeans were grown at day/night temperatures of 22/18 and 26/22°C in sand culture with daily applications of 21.4 mM (high) and 2.1 mM (low) NO₃−N in a complete nutrient solution for durations of 14, 21, and 42 days after emergence and with an N-free solution. Dry matter and N accumulation were greater at 26/22 than 22/18°C. In general, both increased as the level and duration of applied NO₃−N was increased. These increases were attributable to an abbreviation in the interval between emergence and onset of rapid growth. The presence and assimilation of NO₃−N, even at the high level, did not inhibit development of functional nodules. Neither mass nor acetylene reduction activity of nodules was reduced by high NO₃−N; however, the root mass was increased by NO₃−N more than the nodule mass. There was an interaction between temperature and NO₃−N on specific nodule activity as measured by acetylene reduction. The specific nodule activity was unaffected by NO₃−N at 22/18°C, but at 26/22°C the specific activity was lower in the absence of NO₃−N than when NO₃−N was present. Apparently, rapid early growth at 26/22°C depleted cotyledonary reserves of N before nodules became active and, thereafter, the plants were unable to develop adequate leaf area to support nodule development and functioning. This result has implications in N fertilization of late-planted soybeans. Paper number 6637 of the Journal Series of the North Carolina Agricultural Research Service, Raleigh, North Carolina, 27650. The research was supported in part by a grant from the North Carolina Soybean Producers Association and by USDA-SEA-CR grant 701-15-26.