Metabolite profiling of shoot extract,root extract,and root exudate of rice under nitrogen and phosphorus deficiency

ABSTRACT

Root exudate is derived from plant metabolites and its composition is affected by plant nutrient status. A deficiency of mineral nutrients, such as nitrogen (N) and phosphorus (P), strongly affects the type and amount of plant metabolites. We applied a metabolite profiling technique to investigate root exudates of rice plants under N and P deficiency. Oryza sativa was grown in culture solution containing two N levels (0 and 60 mg N L^?1) or two P levels (0 and 8 mg P L^?1). Shoot extracts, root extracts, and root exudates were obtained from the rice plants 5 and 15 days after transplanting and their metabolites were determined by capillary electrophoresis/time-of-flight mass spectrometry. Shoot N concentration and dry weight of rice plants grown at ?N level were lower than those of plants grown at +N level. Shoot P concentration and dry weight of rice plants grown at ?P level were lower than those of plants grown at +P level. One hundred and thirty-two, 127, and 98 metabolites were identified in shoot extracts, root extracts, and root exudates, respectively, at the two N levels. One hundred and thirty-two, 128, and 99 metabolites were identified in shoot extracts, root extracts, and root exudates, respectively, at the two P levels. Seventy-seven percent of the metabolites were exuded to the rhizosphere. The concentrations of betaine, gamma-aminobutyric acid, and glutarate in root exudates were higher at both ?N and ?P levels than at their respective high levels. The concentration of spermidine in root exudates was lower at both ?N and ?P levels than at their respective high levels. The concentrations of the other metabolites in root exudates were affected differently by plant N or P status. These results suggest that rice roots actively release many metabolites in response to N and P deficiency.     

Use of soil color meter for aqueous iron and ammonium measurements

Abstract

In this paper, we proposed a new approach for on-site colorimetric analysis of ferrous ions (Fe²⁺) and ammonium-nitrogen (NH₄ ⁺-N) using a soil color meter as an alternative method to conventional spectrophotometry. The soil color meter we used can express solution color numerically on the basis of L*a*b* color space. After coloring of water by the 1, 10 phenanthroline method and the Indophenol blue method, the color of solution was measured by the soil color meter. A linear relationship between Fe²⁺ and a* or b* values, and systematic change of NH₄ ⁺-N with L* value, enable us to make a calibration curve. The Fe²⁺ and NH₄ ⁺-N concentrations in groundwater samples (Fe²⁺: 0.3–1.3 mg L^?1; NH₄ ⁺-N: 0.02–0.62 mg L^?1) determined by the proposed method agreed well with those determined by conventional spectrophotometry with the difference being ± 0.05 mg L^?1 and ± 0.02 mg L^?1, respectively. Since a similar apparatus is widely used in the soil science field, this technique would facilitate field surveys.     

Analysis of 46-kDa protein in the perivitelline membrane of Japanese quail (Coturnix japonica)

The extracellular matrix surrounding the oocyte before ovulation is called the perivitelline membrane (PL) in avian species. The PL is constructed with two major glycoproteins, ZPC and ZP1, which are synthesized in the ovarian granulosa cells and the liver, respectively. Although the properties of the major components in the PL have been examined, knowledge about the nature of its minor constituents is lacking. In this study we focused on PL protein, which migrates at 46‐kDa in the gel of SDS‐PAGE. N‐terminal sequence analysis demonstrated that the 46‐kDa protein is the C‐terminal fragment of ZP1. Analysis of lysylendopeptidase digests or cyanogens bromide‐degraded fragments of ZP1 confirmed this postulate. Western blot analysis using antiserum against 46‐kDa protein indicated the absence of 46‐kDa protein in the serum. Moreover, small immunoreactive bands, thought to be cleaved fragments of ZP1, were detected in the PL lysate by western blot analysis using antiserum against the N‐terminal peptide of ZP1. These results indicated that the N‐terminal proteolytic processing of ZP1 might take place after the arrival of ZP1 at the ovary, and the resulting product, 46‐kDa protein, is incorporated into the PL.     

Perception and valuation of Paddy Field Dam functions by rural communities: a CVM approach

Paddy and Water Environment - In recent years, Paddy Field Dams have received recognition as a measure to alleviate flooding due to torrential rains. Paddy Field Dams have been in practice in...     

Fire resistance of thick wood-based boards

Thick wood-based boards are used as construction materials for walls and floors in Japan. In this study, fire resistance tests (ISO 834-1) and cone calorimeter tests (ISO 5660-1) were conducted for thick plywood, particleboard, and medium density fiberboard with sample thicknesses of about 28–30mm, and their suitabilities for quasi-fireproof or fire-preventive structures were evaluated. In the ISO 834-1 fire resistance test, the heat-shielding performance (insulation criterion) for walls was evaluated and the results showed that the larger the apparent density of a woodbased board, the higher its insulation performance. The insulation performance of thick wood-based boards in the fire resistance test could be forecast from the results of the cone calorimeter test, especially when the second peak of heat release rate appeared. In the cone calorimeter tests, the surface layer density of the plywood, particleboard, and medium density fiberboard was the dominant parameter for the time to ignition and initial heat release rate. These results indicate that thick wood-based board is a suitable fire-preventive construction material. Part of this study was presented at the Annual Meeting of the Architectural Institute of Japan, Hokkaido, Japan, August 2004