Sequence of the S 9-RNase cDNA and PCR-RFLP system for discriminating S 1- to S 9-allele in Japanese pear

A new S ₉-allele was discovered in 6 Japanese pear cultivars, ‘Shinkou’, ‘Shinsei’, ‘Niitaka’, ‘Amanogawa’, ‘Nangetsu’ and ‘Nansui’. cDNA encoding S ₉-RNase, a stylar product of S ₉-allele, was cloned from pistils of ‘Shinkou’ and ‘Shinsei’ by 3' and 5' RACE. The S ₉-RNase gene had an open reading frame of 684 nucleotides encoding 228 amino acid residues. S ₉-RNase had a hypervariable (HV) region different from S ₁- to S ₈-RNase and shared higher similarity (95.2%) with apple S ₃-RNase than with 8 Japanese pear S-RNases (from 61.0% to 70.7%). Genomic PCR with primers ‘FTQQYQ’ and ‘anti-(I/T) IWPNV’ provided S ₁- to S ₉-amplicon (product), but could not discriminate the S ₂ from the S ₉ of ca. 1.3 kb. The S ₂ and S ₉ were distinguished by digestion with AflII and BstBI, respectively. The digestion with nine S-allele-specific restriction endonucleases, SfcI, AflII, PpuMI, NdeI,AlwNI, HincII, AccII, NruI and BstBI, distinguished S ₁ to S ₉, establishing that this PCR-RFLP system is useful for S-genotype assignments in Japanese pear harboring S ₁- to S ₉-allele. ‘Shinkou’, ‘Shinsei’, ‘Nangetsu’ and ‘Nansui’ assigned as S ₄ S ₉ were determined to be cross incompatible. This revised version was published online in July 2006 with corrections to the Cover Date.     

Effects of NO3- availability on NO3- use in seedlings of three woody shrub species

We determined the effects of short-term cultivation with various amounts of available nitrate nitrogen (NO3-) on NO3- use by woody shrub species. Nitrate concentration ([NO3-]) and nitrate reductase activity (NRA) were measured in leaves and roots of seedlings of Hydrangea hirta (Thunb.) Siebold, Lindera triloba (Sieb. et Zucc.) Blume and Pieris japonica (Thunb.) D. Don. Root [NO3-] increased with increasing NO3- supply in all species, whereas leaf [NO3-] remained low. There were significant correlations between [NO3-] in roots and leaves in all species, but no correlation was found between root NRA and leaf NRA. The low proportion of leaf NO3- assimilation to total NO3- assimilation in all species can be ascribed to the lack of NO3- transport from roots to leaves. In all species, root NRA increased with increasing NO3- supply until reaching a plateau. Species ranking based on maximum root NRA was H. hirta > L. triloba > P. japonica. Root NRA in P. japonica was low, even though root [NO3-] increased with NO3- supply, indicating that NO3- was not an effective N source for this species. The ranking also suggested that H. hirta depended more on NO3- as an N source than L. triloba. The increase in root NRA with increasing NO3- supply was greater in H. hirta than in L. triloba, possibly indicating that a change in NO3- availability has a stronger influence on NO3- use in H. hirta than in L. triloba.     

Dissolved inorganic nitrogen cycling in Banzu intertidal sand-flat,Japan

The sediment-water exchange of nitrogen, nitrification, denitrification and sedimentary oxygen production were simultaneously measured in the Banzu intertidal sand-flat, Tokyo Bay, Japan. The exchange flux across the sediment-water interface showed a sink of dissolved inorganic nitrogen (DIN) in the light. However, in the dark, the intertidal sediment acted as a source. The diffusive flux obtained by the ammonium profile explained only 22% of the source flux directly measured in the dark, suggesting that bioturbation or excretion by macrofauna greatly contributed to the exchange flux. The total microphytobenthic uptake of DIN estimated from O2 productivity and the Redfield ratio was 573.4 ± 64.4 mol N m2 h-1, 31% (175.9 ± 64.4 mol N m-2 h-1) of which was assumed to be derived from the overlying water. The release rate of DIN from the sediment to the water column (1.1 mmol N m-2 day-1) was balanced with the removal rate of DIN from the water column by benthic microalgae on a diurnal basis. This result suggests that DIN was recycled within the sediment, and the microalgae on the sediment surface played a significant role in suppressing the release of mineralized DIN from the sediment. The measured denitrification rate using an acetylene inhibition technique was 99.6 ± 23.5 mol N m-2 h-1. Since the direct supply of nitrate or nitrite from the water column only accounted for 27% of the total denitrification at the highest estimate, nitrogenous oxide in the sediment pool was the major contributor to sedimentary denitrification.     

Topographical differences in soil N transformation using15N dilution method along a slope in a conifer plantation forest in Japan

Soil N transformation was investigated using¹⁵N dilution method along a slope on a conifer plantation forest. Although there was no significant difference in the net N mineralization rates by laboratory incubation, net nitrification rates increased downslope. Gross N transformation by¹⁵N dilution method showed a distinct difference not only on the rates, but also on the main process between the lower and the upper of the slope. Half of minelarized N was immobilized and the other half was left in NH ₄ ⁺ pool at the upper part of the slope, while all of mineralized N was used for immobilization or nitrification and NH ₄ ⁺ pool decreased at the lower of the slope. Soil N transformations were classified into two groups: one was shown below 773 m and the other was shown above 782 m. The incubation with nitrification inhibitor showed that nitrification was mainly conducted by autotrophs irrespective of the position of the slope. Microbial biomass and microbial C/N were similar among the sites. However, the gross mineralization rate was higher below 773 m than above 782 m under similar respiration rates. This suggests that the substrate quality may be one of the controlling factors for soil N transformation. Extractable organic C/N was similar to microbial C/N at the lower of the slope. It indicated that the substrate was more decomposable below 773 m. It is considered that soil N transformation is affected by topographical gradient of moisture and nutrient which makes plant growth and decomposition rate different.     

Soil nitrogen dynamics during stand development after clear-cutting of Japanese cedar (<Emphasis Type="Italic">Cryptomeria japonica</Emphasis>) plantations

We examined soil N dynamics, including inorganic N concentration, net N transformation rates, and estimated plant N uptake (EPNU) from soil N budgets, and litterfall inputs, in five Japanese cedar plantation stands of different ages (5, 16, 31, 42, and 89 years) in the Mt Gomadan Experimental Forest (GEF). Net soil N mineralization and nitrification rates did not differ significantly between the youngest and oldest stands; soil moisture and inorganic N concentration were higher in the youngest stand. The EPNU was highest in the 16-year-old stand and lowest in the 31-year-old stand, and had a significant negative correlation with litter C:N ratio. The oldest (89-year-old) stand had a higher soil C:N ratio, lower proportion of nitrification rate to mineralization rate (%NIT), and higher estimated plant NH₄ ⁺ uptake than did the other stands, indicating that changes of soil organic matter quality can alter soil N dynamics. These results suggest that as a Japanese cedar plantation develops, soil N dynamics can be altered by the quantity and quality of input litter and soil organic matter, and can generate the imbalance between N supply from soil and N demand by plant.     

A device in the determination of si in dithionite-citrate-bicarbonate extract

In the determination of Si in dithionite-citrate-bicarbonate (DCB) extract (2) by the molybdenum blue heteropply method, the color develppment, is interfered by the presence of dithionite and citrate. Weaver el al. (4) have eliminated the interference by introducing air-bubbling for oxidation of the former and by the use of a large excess of molybdate solution as a complexing agent of the latter. This method, while,giving satisfactory results, has a disadvantage that air-bubbling is time-consuming. Moreover it often occurs that the analysis is delayed also due to the limitation of bubbling facilities particularly when many samples are treated at a time.     

Adsorption of polyphosphates by allophane

Although many investigations have been carried out on the reaction of phosphates with allophane as well as with crystalline clays, they have been almost with the orthophosphates (2, 13, 19, 21). Recent investigations have revealed that certain condensed phosphates (polyphosphates) have a considerable promise as a long-term, slow-release source of phosphorus for plants (3, 7, 9, 10. 14, 17. 18, 20. 25). Relatively little information is available, however, on the reaction of those substances with soil clay minerals (8. 15).     

Arsenic extractability with phosphate and citrate from peat collected in Bangladesh

Abstract

Arsenic extractability with various solutions from peat samples collected in Deuli Village, Bangladesh, was investigated to reveal the leaching mechanisms of arsenic in sediments to groundwater. Peat layer was distributed at the depth of 7–8 m in the sediments, and the peat samples collected and used in this experiment contained 137 mg kg^?1 arsenic. A wide range of pH values and concentrations of phosphoric acid and trisodium citrate was used for the extracting solutions. Arsenic extractability with Hel (25–1,000 mM) or NaOH (20–500 mM) at different pH values ranged for 30 to 60% in strong acid or alkali, while was less than 0.1% in the neutral pH range against the total content. Extraction of arsenic with 100 mM phosphoric acid and 100 mM trisodium citrate was about 20% even at a neutral pH, while the extractability with these solutions at concentrations below 1 mM was similar to that with distilled water. These results suggest that competitive exchange and / or chelating action are / is the prior possible mechanism for arsenic leaching from peat. However, the experimental conditions such as pH value or phosphate anion concentration differed from those in the study area where the pH of groundwater was almost neutral and the phosphate anion concentration was only 0.01 mM. Moreover, since the experiment was conducted using a batch system under oxidative conditions and not using a continuous flow system, the importance of the oxidation-reduction potential in the sediments and organic matter content in the groundwater should be investigated.     

Upregulation of the genes for ferritin,RNase, and DnaJ in leaves of rice plants in response to sulfur deficiency

Microarray analysis was carried out with mRNAs isolated from aerial portions of rice plants subjected to sulfur deficiency. Among the candidate clones regulated by sulfur deficiency, three genes were identified by northern analysis that showed altered levels of mRNA accumulation. Genes similar to those for ferritin, S-like ribonuclease, and DnaJ-like protein were down-, down-, and upregulated by sulfate deficiency, respectively. These genes were found for the first time to be responsive to sulfur nutrition in the present study.