Soybean Plant Tissues Research Articles

Nitrate Inhibits Nodule Nitrogen Fixation by Accumulating Ureide in Soybean Plants.

The mechanism by which nitrate inhibits nitrogen fixation in soybean (Glycine max L.) is not fully understood. Accumulation of ureide in soybean plant tissues may regulate the nitrogen fixation capacity through a feedback pathway. In this study, unilaterally nodulated dual-root soybeans prepared by grafting were grown in sand culture. They were subjected to the removal of the nodulated side roots, and were given either nitrate supply or no supply to the non-nodulated side roots for 3 days (experiment I). Additionally, they received nitrate supply to the non-nodulated side roots for 1-14 days (experiment II). The results showed that nitrate supply increased the levels of asparagine and ureide in soybean shoots (Experiment I). In Experiment II, nodule dry weight, nodule number, nodule nitrogenase activity, and nodule urate oxidase activity decreased significantly after 3, 7, and 14 days of nitrate supply. Ureide content in the shoots and nodules increased after 1, 3, and 7 days of nitrate supply, but decreased after 14 days of nitrate supply. There was a significant positive correlation between urate oxidase activity and nitrogenase activity. Hence, we deduced that nitrate supply increased the asparagine content in soybean shoots, likely inhibiting ureide degradation, which induced the accumulation of ureide in soybean shoots and nodules, and, in turn, feedback inhibited the nodule nitrogen fixation. In addition, urate oxidase activity can be used to assess the nitrogen fixation capacity of nodules.

Valorization of soybean plant wastes in preparation of N-doped biochar for catalytic ozonation of organic contaminants: Atrazine degradation performance and mechanistic considerations

Selecting the biomass source is critical because different plants or tissues may exhibit varying textures and chemical properties. However, few researchers have compared the catalytic activity of different tissues from the same plant after carbonization. Soybean is widely cultivated worldwide and always suffers from pests and diseases. The inappropriate storage of harvested soybeans leads to mildew and its wastage. Herein, soybean biochar (SB), soybean shell biochar (SBS), and soy straw biochar (SS) catalysts were prepared using waste soybean plant tissues as precursors, which drastically improved the degradation efficiency of atrazine in catalytic ozonation. The specific reaction rate constant normalized by the surface area (kobs/SBET) of SB during catalytic ozonation indicated the catalytic performance of biochar was not affected just by SBET. The characterization results showed that the delocalized π-electrons, nitrogen-, and oxygen-containing functional groups played key roles in catalytic ozonation, and contributions of these active sites to the generation of both radical and nonradical reactive oxygen species (ROS) including hydroxyl radicals (•OH), superoxide radicals (O2•−), and singlet oxygen (1O2) contributed to atrazine degradation. Compared with SBS and SS, SB contained the highest pyridine N content, the highest carbonyl group (–C = O) content, the strongest delocalized electron density, and electron donor ability, which was responsible for its superior catalytic performance. Such active sites on biochar enhanced the ozone adsorption and decomposition, accelerated the electron transfer process to produce more ROS, and achieved efficient pollutant elimination. Overall, guided by the “waste treating waste” concept, this study provided a valuable alternative in the recycling and reuse of agricultural waste soybean plants, proving that the derived biochar could be potentially used as a catalyst for advanced oxidation processes-based applications.

The effect of 100–200 nm ZnO and TiO2 nanoparticles on the in vitro-grown soybean plants

Engineered nanomaterials are increasingly used in everyday life applications and, in consequence, significant amounts are being released into the environment. From soil, water, and air they can reach the organelles of edible plants, potentially impacting the food chain and human health. The potential environmental and health impact of these nanoscale materials is of public concern. TiO2 and ZnO are among the most significant nanomaterials in terms of production amounts. Our study aimed at evaluating the effects of large-scale TiO2 (~100 nm) and ZnO (~200 nm) nanoparticles on soybean plants grown in vitro. The effect of different concentrations of nanoparticles (10, 100, 1000 mg/L) was evaluated regarding plant morphology and metabolic changes. ZnO nanoparticles showed higher toxicity compared to TiO2 in the experimental set-up. Overall, elevated levels of chlorophylls and proteins were observed, as well as increased concentrations of ascorbic and dehydroascorbic acids. Also, the decreasing stomatal conductance to water vapor and net CO2 assimilation rate show higher plant stress levels. In addition, ZnO nanoparticle treatments severely affected plant growth, while TEM analysis revealed ultrastructural changes in chloroplasts and rupture of leaf cell walls. By combining ICP-OES and TEM results, we were able to show that the nanoparticles were metabolized, and their internalization in the soybean plant tissues occurred in ionic forms. This behavior most likely is the main driving force of nanoparticle toxicity.

Response of Corn-Soybean Intercropping to Fertilizer Packages in Dry Land with Dry Climate

Intercropping soybean with corn on dry land with dry climate (DLDC) is an alternative program to expand the soybean cultivation harvested area. This study evaluated the effectiveness of fertilization performance in the intercropping of soybean-corn in DLDC. The experiment in this study was arranged in a randomized block design, consisting of seven fertilizer package treatments with four replications. The spacing between corn (Pertiwi 3) and soybean (Dena 1) was (50 cm x 200 cm) x 40 cm (2 plants/clump) and between soybeans (Dena 1) was 40 cm x 15 cm (2-3 plants/clumps). The observations consisted of soil analysis (pH, organic matter, total N (Kjeldahl), available P, Ca-dd, Mg-dd, K-dd, and Na-dd), soybean leaf chlorophyll index (45 and 60 days after planting/dap), plant height at (45 daps and harvest), number and weight of root nodules (45 daps); Corn: chlorophyll index (56 daps), plant height (harvest), analysis of corn and soybean plant tissue (60 daps), yield, and yield components of dry seeds of soybean and corn per hectare. The results showed that effective fertilization for the intercropped crops was 53 kg N + 1,500 kg of manure per hectare in corn plant and 7 kg N + 22 kg P2O5 + 18 kg K2O + 1,500 kg/ha manure + Rhizobium Iletrisoy/Agrisoy in soybean crops.

Exposure and Transport of Alkaloids and Phytoestrogens from Soybeans to Agricultural Soils and Streams in the Midwestern United States.

Phytotoxins are naturally produced toxins with potencies similar/higher than many anthropogenic micropollutants. Nevertheless, little is known regarding their environmental fate and off-field transport to streams. To fill this research gap, a network of six basins in the Midwestern United States with substantial soybean production was selected for the study. Stream water (n = 110), soybean plant tissues (n = 8), and soil samples (n = 16) were analyzed for 12 phytotoxins (5 alkaloids and 7 phytoestrogens) and 2 widely used herbicides (atrazine and metolachlor). Overall, at least 1 phytotoxin was detected in 82% of the samples, with as many as 11 phytotoxins detected in a single sample (median = 5), with a concentration range from below detection to 37 and 68 ng/L for alkaloids and phytoestrogens, respectively. In contrast, the herbicides were ubiquitously detected at substantially higher concentrations (atrazine: 99% and metolachlor: 83%; the concentrations range from below detection to 150 and 410 ng/L, respectively). There was an apparent seasonal pattern for phytotoxins, where occurrence prior to and during harvest season (September to November) and during the snow melt season (March) was higher than that in December-January. Runoff events increased phytotoxin and herbicide concentrations compared to those in base-flow conditions. Phytotoxin plant concentrations were orders of magnitude higher compared to those measured in soil and streams. These results demonstrate the potential exposure of aquatic and terrestrial organisms to soybean-derived phytotoxins.

Chromatographic determination of shikimate for identification of conventional soybean and glyphosate resistant soybean

A sensitive and reliable process was established using high-performance liquid chromatography (HPLC) to distinguish conventional varieties of glyphosate-resistant genetically modified crops via shikimate detection in soybean (Glycine max L. Merril) seeds. Glyphosate has a well-defined mechanism of action. It is the only herbicide that specifically inhibits 5-enolpiruvilshikimate-3-phosphate synthase (EPSPS E.C. 2.5.1.19), which catalyzes the condensation of shikimate with phosphoenolpyruvate. This study is based on the concept that shikimate significantly accumulates in soybean plant tissues after EPSPS inhibition by glyphosate. In plants not subjected to glyphosate, shikimate is not easily detected because it quickly metabolizes into shikimate 3-phosphate and subsequently into 5-enolpiruvilshikimate 3-phosphate through the action of EPSPS. Conversely, in non-genetically modified plants subjected to glyphosate, shikimate metabolism is impaired, resulting in its accumulation. This metabolite can be detected in extremely low quantities (in the microgram range), through HPLC. In this study, six different contrasts were analyzed, each being formed by a transgenic cultivation and its parental strain, subject or not subject to the treatment of soaking with a 0.6% glyphosate solution. Chromatographic analyses indicated shikimate accumulation only in conventional cultivars with seeds previously soaked in a 0.6% glyphosate solution. Thus, this shikimate detection method can be used as a rapid and accurate means to distinguish soybeans with glyphosate-resistant qualities.

Effects of endophytic entomopathogenic fungi on soybean aphid and identification of Metarhizium isolates from agricultural fields.

Terrestrial plants can harbor endophytic fungi that may induce changes in plant physiology that in turn affect interactions with herbivorous insects. We evaluated whether the application of entomopathogenic fungi Beauveria bassiana and Metarhizium brunneum to soybean seeds could become endophytic and affect interactions with soybean aphid (Aphis glycines Matsumura). It was found that A. glycines population sizes increased on plants with M. brunneum (strain F52) seed inoculum, but no significant effects were shown with analogous treatments with B. bassiana (strain GHA). Fungi recovered from soybean plant tissues indicate that endophytism was established, and that B. bassiana was more prevalent. Metarhizium brunneum was only recovered from stems, but B. bassiana was recovered from stems and leaves. This work confirms that some entomopathogenic fungi can be endophytic in soybean, however, some of these fungi may have a negative effect on the plants by increasing susceptibility of soybean to A. glycines. We also used DNA sequence data to identify species of Metarhizium obtained from agricultural fields in Iowa. Phylogenetic analyses, based on DNA sequence data, found that all isolates were Metarhizium robertsii, which is consistent with past studies indicating a cosmopolitan distribution and wide host range for this species. These results are important for understanding the dynamics of implementing environmentally sustainable measures for the control of pest insects.

Lipidomic analysis of soybean leaves revealed tissue-dependent difference in lipid remodeling under phosphorus-limited growth conditions.

Lipid remodeling in soybean under phosphorus (P)-limitation stress was investigated via lipidomic analysis. Principle component analysis of lipidome data from plants with 4 unfolded trifoliate leaves revealed that each leaf responded to P-limitation stress differently. Upon P limitation, a substantial decrease in phospholipids was observed particularly in the 1st and 2nd trifoliate leaves, while 3rd, and especially 4th, trifoliate leaves showed lipid profiles similar to those from control plants grown under P sufficiency. Under P-limited conditions, non-phosphorus glycoglycerolipid, glucuronosyldiacylglycerol (GlcADG), significantly increased in the 1st and 2nd trifoliate leaves. The levels of some other non-phosphorus glycoglycerolipids, including monogalactosyldiacylglycerol, digalactosyldiacylglycerol, and sulfoquinovosyldiacylglycerol (SQDG), were elevated under P-limited growth conditions, while there were only slight changes in the total levels of these lipid classes upon P limitation. These results indicate that the lipid metabolic pathway in tissues of soybean plants does not uniformly respond to P-limitation stress, where lipid remodeling is very active in older leaves and phosphate appears to be preferentially remobilized to the younger tissues under P-limited conditions.

Optimization and Application of a Quantitative Polymerase Chain Reaction Assay to Detect Diaporthe Species in Soybean Plant Tissue

Diaporthe caulivora and D. longicolla are the causal agents of stem canker of soybean (Glycine max L.). Accurate identification of stem canker pathogens upon isolation from infected soybean plants is difficult and unreliable based on morphology. In this study, two TaqMan probe-based quantitative polymerase chain reaction (qPCR) assays were optimized for detection of D. caulivora and D. longicolla in soybean plants. The assays used previously reported D. caulivora-specific (DPC-3) and D. longicolla-specific (PL-3) probe/primer sets. The sensitivity limit of the two assays was determined to be over a range of 100 pg to 10 fg of pure D. caulivora and D. longicolla genomic DNA. The qPCR assays were validated with plant samples collected from commercial soybean fields. The PL-3 set detected D. longicolla in soybean plants collected from the fields (quantification cycle value <35), which was confirmed by isolation on potato dextrose agar (PDA). D. caulivora was detected only in low levels (quantification cycle value <40) by DPC-3 set in a few of the symptomatic field samples, although the pathogen was not isolated on PDA. The qPCR assays were also useful in quantitatively phenotyping soybean plants for resistance to D. caulivora and D. longicolla under greenhouse conditions.

First Report of Seedborne Fusarium thapsinum and its Pathogenicity on Soybean (Glycine max) in the United States.

A three-year survey from 2010 to 2012 was conducted in Kansas to investigate the identity and diversity of seedborne Fusarium spp. in soybean. A total of 408 soybean seed samples from 10 counties were tested. One hundred arbitrarily selected seeds from each sample were surface-sterilized for 10 min in a 1% sodium hypochlorite solution to avoid contaminants and promote the isolation of internal fusaria. Seeds were rinsed with sterile distilled water and dried overnight at room temperature (RT). Surface-sterilized seeds were plated on modified Nash-Snyder medium and incubated at 23 ± 2°C for 7 days. Fusarium isolates were single-spored and identified by morphological characteristics on carnation leaf agar (CLA) and potato dextrose agar (PDA) (3). From 276 seedborne Fusarium isolates, six were identified as F. thapsinum (2). On CLA, F. thapsinum isolates produced abundant mycelium and numerous chains of non-septate microconidia produced from monophialides. Microconidia were club-shaped and some were napiform. No chlamysdospores were found. On PDA, three of the isolates presented characteristic dark yellow pigmentation and three were light violet. Confirmation of the isolates to species was based on sequencing of an elongation factor gene (EF1-α) segment using primers EF1 and EF2 and the beta-tubulin gene using primers Beta1 and Beta2 (1). Sequence results (~680 bp, EF primers; ~600 bp, beta-tubulin primers) were confirmed by using the FUSARIUM-ID database (1). All isolates matched F. thapsinum for both genes sequenced (Accession No. FD01177) at 99% identity. Koch's postulates were completed for two isolates of F. thapsinum under greenhouse conditions. Soybean seeds (Asgrow AG3039) were imbibed with 2.5 × 105 conidia ml-1 for 48 h. After inoculation, seeds were dried for 48 h at RT. One isolate each of F. equiseti and F. oxysporum were used as the non-pathogenic and pathogenic inoculation controls, respectively. In addition, non-inoculated seeds and seeds imbibed in sterile distilled water (mock) were also used. Twenty-five seeds from each treatment were planted in pots (500 ml) with autoclaved soil and vermiculite (1:1). The experiment was a completely randomized design with three replicates (pots) per isolate. The entire experiment was repeated three times. After 21 days, aggressiveness of both F. thapsinum isolates was assessed using initial stand (%), final stand (%), and seed mortality (% of non-germinated seeds). Both seedborne F. thapsinum isolates caused reduced emergence and final stand, and increased seedling mortality when compared to the non-inoculated and F. equiseti controls (P< 0.0001). No significant difference was observed between F. thapsinum isolates and F. oxysporum. F. thapsinum isolates were re-isolated from wilted seedlings and non-germinated seeds, but not from the control treatments. Typically, F. thapsinum is considered a pathogen of sorghum, but it has also been recovered from bananas, peanuts, maize, and native grasses (3). However, its presence on soybean plant tissues and its pathogenicity has never been reported. To our knowledge, this is the first report of seedborne F. thapsinum and its pathogenicity on soybean in the United States.

Relationships between Microsclerotia Content and Hyperspectral Reflectance Data in Soybean Tissue Infected by Macrophomina phaseolina

Alternative methods are needed to assess the severity of charcoal rot disease [Macrophomina phaseolina (Tassi) Goid] in soybean [Glycine max (L.)] plant tissue. The objective of this study was to define the relationship between light reflectance properties and microsclerotia content of soybean stem and root tissue. Understanding that relationship could lead to using spectral reflectance data as a tool to assess the severity of charcoal rot disease in soybean plants, thus reducing human bias associated with qualitative analysis of soybean plant tissue and cost and time issues connected with quantitative analysis. Hyperspectral reflectance measurements (400-2490 nm) were obtained with a non-imaging spectroradiometer of non-diseased and charcoal rot diseased ground stem and root tissue samples of six soybean genotypes (“Clark”, “LD00-3309”, “LG03- 4561-14”, “LG03-4561-19”, “Saline”, and “Y227-1”). Relationships between the reflectance measurements and tissue microsclerotia content were evaluated with Spearman correlation (rs) analysis (p < 0.05). Moderate (rs = ±0.40 to ±0.59), strong (rs = ±0.60 to ±0.79), and very strong (rs = ±0.80 to ±1.00) negative and positive statistically significant (p < 0.05) monotonic relationships were observed between tissue spectral reflectance values and tissue microsclerotia content. Near-infrared and shortwave-infrared wavelengths had the best relationships with microsclerotia content in the ground tissue samples, with consistent results obtained with near-infrared wavelengths in that decreases in near-infrared spectral reflectance values were associated with increases in microsclerotia content in the stem and root tissue of the soybean plants. The findings of this study provided evidence that relationships exist between tissue spectral reflectance and tissue microsclerotia content of soybean plants, supporting spectral reflectance data as a means for assessing variation of microsclerotia content in soybean plants. Future research should focus on the modelling capabilities of the selected wavelengths and on the feasibility of using these wavelengths in machine learning algorithms to differentiate non-diseased from charcoal rot diseased tissue.

First Report of Soybean vein necrosis virus on Soybeans in Michigan.

Soybean vein necrosis virus (SVNV) is associated with an emerging disease in soybean producing regions of the United States. Soybean leaves with necrotic vein symptoms were initially noted in 2008 or 2009 in fields across Arkansas, Kansas, Missouri, Illinois, Mississippi, Tennessee, and Kentucky and SVNV was determined to be the causal agent (2). In 2012, widespread reports of SVNV were made across most soybean (Glycine max) producing states including the recent confirmation of SVNV in Iowa and Wisconsin (1). Foliar symptoms similar to those reported for SVNV were observed at approximately 1 to 10% incidence in soybean fields across Michigan in late August and September of 2012, including fields located in Cass, Ingham, Midland, Saginaw, and Van Buren counties. Symptoms included chlorosis and necrosis which initiated on the veins with subsequent spread across the leaf. An initial sample collected from the East Lansing Agricultural Research Station was confirmed to have SVNV with a polyclonal antibody using double antibody sandwich (DAS)-ELISA at AC Diagnostics, Inc. (Fayetteville, AR) and with reverse transcription PCR by Ioannis Tzanetakis, University of Arkansas, Fayetteville. Additional samples from five fields were subsequently collected from Cass, Ingham, and Van Buren counties. Duplicate leaf tissue samples were tested with DAS-ELISA using the SVNV test kit (AC Diagnostics). All symptomatic leaf samples exhibited a strong positive reaction based on the optical density reading at 405 nm. Absorbance reading that exceeded the healthy soybean tissue by a standard deviation of +3× were considered positive. Total RNA was also extracted from each sample using the RNeasy Plant Mini Kit (Qiagen, Germantown, MD). Complementary DNA (cDNA) was generated using virus-specific LdetR and SdetR primers (2) with the High Capacity RT cDNA kit (Life Technologies; Carlsbad, CA). The cDNA was used as template for PCR with the SVNV-specific primers that amplify regions of the L (LdetF/LdetR) and the S (SdetF/SdetR) RNAs (1). Amplification products of the expected 297 and 861 bp size, respectively, were detected in all symptomatic samples while no amplification products were generated from healthy soybean plant tissues grown under greenhouse conditions. Significantly, this is the first documentation and confirmation of the widespread prevalence of SVNV across the state of Michigan in 2012.

생활하수 및 산업폐수 슬러지 처리에 따른 콩의 중금속 및 아미노산 함량

본 연구는 생활하수 및 산업폐수 슬러지를 연차적으로 경작지에 처리한 후, 재배된 콩 식물체의 중금속 흡수 정도와 영양성분에 미치는 영향을 조사하였다. 처리량은 무처리, 11.25, 22.50 및 45.00 Mg/ha로 하였으며, 재배된 콩 식물체의 부위별 Cd, Pb, Ni, Cu 및 Zn 함량과 콩 종실의 수확량, 단백질 및 아미노산 함량을 조사하였다. 콩 종실 중의 Cd 함량은 0.02～0.05 mg/kg으로 기준치에 안전한 수준이었고, Pb 함량은 산업폐수 슬러지 45 Mg/ha를 제외하고 0.02～0.15 mg/kg으로 기준치에 적합하였다. 또한, 모든 중금속축적률은 잎 또는 뿌리보다 식용부위인 콩 종실에서 상대적으로 낮았고, 슬러지 처리량의 증가에도 함량 변화는 적어 식용으로서 안전함을 확인하였다. 종실의 수확량은 1년차에 슬러지 처리군이 무처리군보다 높았지만 2년차에는 생활하수 슬러지의 경우 낮은 수확량을 보였고, 산업폐수 슬러지의 경우 유사한 수준 또는 감소하는 경향이었다. 생활하수 슬러지 처리에 따른 아미노산 함량은 glutamate 경우에만 슬러지 처리군이 무처리군보다 증가하는 경향이었다. 하지만 연용에 따른 변화는 12종에서만 무처리군보다 증가하고 있었다. 산업폐수 슬러지는 1년차의 경우 15종이 무처리군에서 가장 높았고, 2년차에서는 11.25 Mg/ha에서 17종 모두가 가장 높은 결과를 나타내었다. 결론적으로 콩 종실 중 중금속 축적량은 문제가 되지 않았으나 수량이 감소되는 점을 감안할 때 가장 적합한 슬러지 처리 수준은 11.25 Mg/ha임을 확인하였다.

Differential gene expression in soybean leaf tissues at late developmental stages under drought stress revealed by genome-wide transcriptome analysis.

The availability of complete genome sequence of soybean has allowed research community to design the 66 K Affymetrix Soybean Array GeneChip for genome-wide expression profiling of soybean. In this study, we carried out microarray analysis of leaf tissues of soybean plants, which were subjected to drought stress from late vegetative V6 and from full bloom reproductive R2 stages. Our data analyses showed that out of 46093 soybean genes, which were predicted with high confidence among approximately 66000 putative genes, 41059 genes could be assigned with a known function. Using the criteria of a ratio change > = 2 and a q-value<0.05, we identified 1458 and 1818 upregulated and 1582 and 1688 downregulated genes in drought-stressed V6 and R2 leaves, respectively. These datasets were classified into 19 most abundant biological categories with similar proportions. There were only 612 and 463 genes that were overlapped among the upregulated and downregulated genes, respectively, in both stages, suggesting that both conserved and unconserved pathways might be involved in regulation of drought response in different stages of plant development. A comparative expression analysis using our datasets and that of drought stressed Arabidopsis leaves revealed the existence of both conserved and species-specific mechanisms that regulate drought responses. Many upregulated genes encode either regulatory proteins, such as transcription factors, including those with high homology to Arabidopsis DREB, NAC, AREB and ZAT/STZ transcription factors, kinases and two-component system members, or functional proteins, e.g. late embryogenesis-abundant proteins, glycosyltransferases, glycoside hydrolases, defensins and glyoxalase I family proteins. A detailed analysis of the GmNAC family and the hormone-related gene category showed that expression of many GmNAC and hormone-related genes was altered by drought in V6 and/or R2 leaves. Additionally, the downregulation of many photosynthesis-related genes, which contribute to growth retardation under drought stress, may serve as an adaptive mechanism for plant survival. This study has identified excellent drought-responsive candidate genes for in-depth characterization and future development of improved drought-tolerant transgenic soybeans.

Molecular characterization of GmNHX2, a Na+/H+ antiporter gene homolog from soybean, and its heterologous expression to improve salt tolerance in Arabidopsis

Na+/H+ antiporters have been well documented to enhance plant salt tolerance by regulating cellular ion homeostasis. Here, a putative Na+/H+ antiporter gene homolog GmNHX2 from soybean was cloned and predicted to encode a protein of 534 amino acids with 10 putative transmembrane domains. GmNHX2 was expressed in all soybean plant tissues but enriched in roots and its expression was induced by NaCl and polyethylene glycol (PEG) treatments. GmNHX2 exhibits greater sequence similarity with LeNHX2 and AtNHX6 than that of AtNHX1 and AtSOS1. Although phylogenetic analysis clustered GmNHX2 with organellar (tonoplast and vesicles) antiporters, the GmNHX2-EGFP (enhanced green fluorescent protein) fusion protein was possibly localized in the plasma membrane or organelle membrane of transgenic plant cells. Furthermore, transgenic Arabidopsis plants expressing GmNHX2 were more tolerant to high NaCl concentrations during germination and seedling stages when compared with wild-type plants. These results suggest that GmNHX2 is a membrane Na+/H+ antiporter and may function to regulate ion homeostasis under salt stress.

Real-time imaging of radioisotope labeled compounds in a living plant

We developed a quantitative, real-time imaging system of labeled compounds in a living plant. The system was composed of CsI scintillator to convert β-rays to visible light and an image intensifier unit (composed of GaAsP semiconductor and MCP; micro channel plate) to detect extremely weak light. When the sensitivity and resolution of the image of our system was compared with that of an imaging plate (IP), the sensitivity of our system (with 20 minutes) was higher than that of an IP, with similar quality to that of an IP. Using this system, the translocation of 32P in a soybean plant tissue was shown in successive images.

Arbuscular Mycorrhizal Fungi Enhance Zinc and Nickel Uptake from Contaminated Soil by Soybean and Lentil

ABSTRACT Generally, soils in Pakistan are deficient in P and N. Due to intensive cropping and irrigation, Pakistani soils have also become deficient in micronutrients such as Zn, Fe, Cu, and Mn. Arbuscular mycorrhizal fungi, which form symbiotic associations with roots of most land plants, are known to enhance uptake of P and trace elements such as Cu, Ni, Pb, and Zn. The present study was conducted to investigate the role of arbuscular mycorrhizae (AM) in uptake of nickel (Ni) and zinc (Zn) by crops viz. soybean (Glycine max (L.) Merrill) and lentil (Lens culinaris Medic). Zn and Ni were applied as ZnSO4 7H2O and NiCl2 respectively, in four concentrations (0.0, 1.0, 3.0, and 5.0 g kg-1 soil). AM inoculum consisted of sand containing sporocarps, spores, and AMF infected root pieces from a pot culture of Glomus mosseae. Control plants received pot culture filtrate containing soil microflora minus AM fungal propagules. A significant difference (p < 0.05) was observed in the dry weights of roots and shoots of the mycorrhizal (M) and nonmycorrhizal (NM) cereal plants. The sievate-amended treatments did not stimulate plant growth to the same extent as the AM fungal amended treatments. Trace metals inhibited the extent of mycorrhizal colonization of the cereal roots. The concentrations of the trace metals in the plant tissues of 12-week old cereal plants were found significantly (p < 0.05) higher in M than NM plants. These results indicate that mycorrhize can be used as effective tools to supply sufficient Zn in generally Zn-deficient Pakistani soils and to ameliorate the toxicity of trace metals in polluted soils. The contents of Ni in mycorrhizal soybean plant tissues were higher than those in the mycorrhizal lentil plant tissues. The implications of these results in mycorrhizo remediation of agricultural soils are discussed.

Immunodetection ofPhomopsisSpecies in Asymptomatic Soybean Plants

An immunodiagnostic assay was developed for early detection of Phomopsis phaseoli, cause of pod and stem blight, and P. longicolla, cause of seed decay of soybeans (Glycine max), in asymptomatic soybean plant tissue using polyclonal antibodies developed against P. longicolla. Immunoblot analysis of the immunogen and cross-reactive fungal antigens showed a broad smear above 50 kDa. Analyses of P. longicalla and 17 other common soybean parasitic or saprophytic fungi resulted in strong reactions with all Phomopsis spp. and Colletotrichum truncatum (.)

Studies on the Multiplication and Movement of Soybean Mosaic Virus within Soybean Plant Tissues

Studies on the Multiplication and Movement of Soybean Mosaic Virus within Soybean Plant Tissues

Ureide Catabolism by Soybean [ Glycine max (L.) Merrill] Cell Suspension Cultures II: Assimilation of Allantoin

Summary Ureide catabolism was studied in a soybean [Glycine max (L.) Merrill] cell suspension culture growing on the ureide, allantoin, as sole nitrogen source. When enzymes for ureide catabolism were compared between cells grown on allantoin or inorganic nitrogen salts as the sole nitrogen source, allantoinase activity levels were similar while allantoate amidohydrolase activity was lower in cells grown on NH4+/NO3−. This latter activity could be increased to higher levels by the addition of allantoin or ureide precursors to the culture medium. Glutamate dehydrogenase and glutamate synthase activities of NH4+/NO3−-grown cells were higher than allantoin-grown cells while glutamine synthetase and several aminotransferases showed little difference in cells grown on the different nitrogen sources. Studies utilizing [7-14C] and [4,5-14C]allantoin showed that label in the urea moiety was released as CO2 while label from the [4,5-14C]allantoin glyoxylate moiety was incorporated into glycine and serine. The exact pathway from allantoic acid to glyoxylate was not determined due to our inability to detect intermediate compounds. The ureide analog, hydantoic acid, was found to be an excellent nitrogen source for soybean cell suspension growth and an alternate substrate to allantoic acid for in vitro enzymic ammonium release. The data indicates that the entire allantoic acid molecule may be catabolized by the enzyme allantoate amidohydrolase or possibly, a separate amidohydrolase. The ureide catabolism pathway of soybean cell suspensions was similar to the pathway recently reported for tissues of soybean plants.