The relative distribution of 22 mineral elements in the roots, nodules and shoots of the soybean (Glycine max L. Merr. cv. Tsurumusume) at R1 (beginning of the flowering stage) and R7 (beginning of the mature stage) was investigated in response to ammonium and manure N treatment. Plants receiving only atmospheric nitrogen served as the negative control. The addition of ammonium sulfate to the soil caused soil acidification, induced Al and Mn toxicities, and significantly reduced the biomass production in roots and nodules. Ca, Mg, Fe, Mn, Cu, and Zn concentrations were significantly higher in shoots, and those of Mo and Co higher in nodules. The addition of manure to the soil significantly enhanced the levels of Sr, Ba, Cr, and Cd in shoots, whereas the concentration of Cs was decreased at R7. Moreover, when the soybean developed from R1 to R7, the levels of essential elements in nodules decreased, whereas those of nonessential elements increased, irrespective of the nitrogen source. Furthermore, the variation in the concentrations of many elements was not consistent for nodules and roots when soybean developed from R1 to R7. The variation of Mn, Zn, B, and Al concentrations was independent of N treatments. However, Ca, Fe, Cu, Mo, and Se levels were affected strongly by N treatments. This study is the first to document the dynamic variation of the soybean ionome in nodules, roots, and shoots from vegetative to reproductive stage of soybean.

The nitrogen (N) status of a plant determines the composition of its major components (amino acids, proteins, carbohydrates and organic acids) and, directly or indirectly, affects the quality of agricultural products in terms of their calorific value and taste. Although these effects are guided by changes in metabolic pathways, no overall metabolic analysis has previously been conducted to demonstrate such effects. Here, metabolite profiling using gas chromatography-mass spectrometry (GC-MS) was used to evaluate the effect of N levels on spinach tissue, comparing two cultivars that differed in their ability to use N. Wide variation in N content was observed without any distinct inhibition of growth in either cultivar. Principal component analysis (PCA) and self-organizing mapping (SOM) were undertaken to describe changes in the metabolites of mature spinach leaves. In PCA, the first component accounted for 44.5% of the total variance, the scores of which was positively correlated with the plant's N content, and a close relationship between metabolite profiles and N status was observed. Both PCA and SOM revealed that metabolites could be broadly divided into two types, correlating either positively or negatively with plant N content. The simple and co-coordinated metabolic stream, containing both general and spinach-specific aspects of plant N content, will be useful in future research on such topics as the detection of environmental effects on spinach through comprehensive metabolic profiling.

Two field experiments were conducted to investigate the effects of previous cultivation of an arbuscular mycorrhizal (AM) host plant and manure application on the concentration of 19 mineral elements in soybean ( Glycine max L. Merr. cv. Tsurumusume) seeds. Each experiment ran for two years (experiment 1 took place in 2007-2008, and experiment 2 took place in 2008-2009) with a split plot design. Soybeans were cultivated after growing either an AM host plant (maize, Zea mays L. cv. New dental) or a non-AM host plant (buckwheat, Fagopyrum esculentum Moench. cv. Kitawase-soba) in the first year in the main plots, with manure application (0 and 20 t/ha) during the soybean season in split plots from both main plots. On the basis of the two experiments, manure application significantly increased the available potassium (K) and decreased the available iron (Fe) and cesium (Cs) in the soil. However, higher concentrations of cadmium (Cd) and barium (Ba) and lower concentrations of Cs in the seed were induced by the application of manure. Cd levels in the seed were decreased by prior cultivation with the AM host plant. The present study showed that the identity of the prior crop and manure application changed the mineral contents of the soybean seed and suggests a connection between environmental factors and food safety.

In this study, we determined the capacity of soybean (Glycine max L. Merr. cv. Hoyoharuka) and sorghum (Sorghum bicolor L. Moench. cv. Hybrid Sorgo) to utilize different forms of nitrogen (N) in a rhizobox system. Seedlings were grown for 35 days without N or with 130 mg N kg soil as ammonium sulfate or farmyard cattle manure. The soil fractions at different distances from the root were sliced millimeter by millimeter in the rhizobox system. We assessed the distribution of different forms of N and microbial metabolism in different soil fractions in the rhizosphere. There are no treatment-dependent changes in biomass production in the roots and shoots of soybeans, however, the ammonium and manure treatment yielded 1.30 and 1.40 times higher shoot biomass of sorghum than the control. Moreover, the depletion of inorganic N and total amino acids (TAA) in the rhizosphere was largely undetectable at various distances from the soybean roots regardless of the treatments employed. The addition of ammonium sulfate resulted in a decrease in the nitrate concentration gradient as the distance decreased from the sorghum roots. The addition of manure to the soil increased the N content in the sorghum shoots, 1.57 times higher than the control; this increase was negatively correlated with the concentrations of TAA in the soil of the root compartment. In addition, the application of manure simultaneously induced TAA depletion (i.e., the TAA concentration in root compartment was 1.48 times higher than that in bulk soil) and greater microbial activity and diversity in the sorghum rhizosphere, where higher microbial consumption of asparagine, glutamic acid, and phenylalanine were also observed near the roots. Our results are first to present the evidence that sorghum may possess a high capacity for taking up amino acids as a consequence of organic matter application, and microbial metabolism.