Contribution of charcoal to short-term nutrient dynamics after surface fire in the humus layer of a dwarf bamboo-dominated forest

Ecological function of charcoal has been mainly investigated by adding charcoal to soil, which is not fully adequate to understand in situ the role in fire-prone forest ecosystem. To determine in situ effects of charcoal on ecosystem functions, such as nutrient availability, we conducted an experimental burning in a Japanese white birch forest with dense coverage of dwarf bamboo in the understory with or without removal of charcoal. Ammonium-N in the remaining humus layer increased immediately after the burning, but decreased to the level of unburnt plots within 1?month of the burning. Removal of charcoal had no significant effect on the NH₄ ⁺-N dynamics. Although burning did not affect NO₃ ^?-N dynamics during the sampling period, charcoal removal led to a slight increase in NO₃ ^?-N. The available P increased immediately after the burning, but then fell at 1?month after burning. Charcoal inhibited the available P depletion and prolonged the high availability of P. Greater availability of P might be due to the adsorption of phosphate in charcoal pores. Exchangeable Ca and Mg increased gradually; charcoal appeared to extend the period of higher concentration of exchangeable Ca and Mg. Charcoal deriving from fire is a key factor in influencing available nutrient in the humus layer of post-fire forests.     

Intensification of arsenic toxicity to paddy rice by hydrogen sulfide and ferrous iron

Abstract

The phytotoxicity of arsenic to paddy rice was examined by the pot culture method using Utsunomiya grey lowland soil which had received nutrient salts including ammonium sulfate with or without additional rice straw powder as a reducing agent.

By treatment with 50 ppm of arsenic and straw, plant growth was retarded from the beginning of culture, and about 6 weeks later, at the middle of July, small reddish black spots emerged near the tips of expanded green leaves. The spots then increased and spread over the whole leaves resulting in bronzing and final dieback in about the mid-August. On treatment with higher concentrations of arsenic and straw, the plants were more severely injured and died through bronzing at earlier stages. All such dead plants were found to have accumulated abnormally high iron in their leaf tissues. On treatment with lower concentrations of arsenic and straw or in the case of higher arsenic without straw, plant growth and grain yield were reduced with the occurrence of partial bronzing or oranging of leaves and the iron content of the plants was somewhat increased.

These results indicate that arsenic may induce ferrous iron toxicity which intensifies the toxicity of arsenic to paddy rice.     

The effect of slag on paddy rice

To raise more rice in Japan we have placed much fertilizers in the fields, thus the soils often have been degraded by the leaching of essential elements including Fe to such a extent as rice roots are injured by the H₂S produced by the reduction of sulphates. It has been encouraged by law to place non-sulphate fertilizers and iron compounds in these fields.     

Effect of rice straw on the composition of volatile soil gas and micro flora in the tropical paddy field

The effect of rice straw on the composition of volatile soil gas and microflora in the tropical paddy field was studied with and without fertilizer application.

The volatile soil gas most abundantly found in plots with rice straw was methane followed by other gases, nitrogen, oxygen and carbon dioxide during the early stage of rice growth, while nitrogen predominated in later stages.

The loss of soil nitrogen through volatilization increased following phosphorus application as well as rice straw application as compared with that in the control plot. In the former case, the enhancement of decomposition of organic-N was assumed to be due to the increase in population of cellulose decomposer.

Rice straw application with or without N-fertilizer increased methane gas formation by 27 to 63 times as compared with the phosphorus plot and the peak of its formation was found 5 to 7 weeks after rice straw application. However methane formation in the control plot was very low and was found only 5 to 9 weeks after flooding.

Rice straw application usually increased the number of various groups of microorganisms along with contributing to the transformation of organic-N to N₂ gas. But the stimulating effect was chiefly observed in the population of Azotobacter.     

Effect of flutianil on the morphology and gene expression of powdery mildew

Flutianil, a fungicide effective only on powdery mildew, was previously reported to affect the host cell''s haustorial formation and nutrient absorption. Studies were conducted to investigate flutianil''s primary site of action on Blumeria graminis morphology using transmission electron microscope (TEM) observation and RNA sequencing (RAN-seq) techniques. TEM observation revealed that flutianil caused the extra-haustorial matrix and fungal cell wall to be obscured, without remarkable changes of other fungal organelles. RNA-seq analysis indicated that, unlike other powdery-mildew fungicides, flutianil did not significantly affect the constantly expressed genes for the survival of B. graminis. Genes whose expression is up- or downregulated by flutianil were found; these are the three sugar transporter genes and various effector genes, mainly expressed in haustoria. These findings indicate that the primary site of action of flutianil might be in the haustoria.     

Effects of Polybrominated Diphenol Ethers from a Marine Sponge Phyllospongia dendyi on IL-8 Production in a PMA-stimulated Promyelocytic Leukemia Cell Line

The effects of five polybrominated diphenol ethers from a Marine Sponge, Phyllospongia dendyi, on the relative plating efficiencies in V79 cells and the cell proliferation and IL-8 production in PMA-stimulated HL-60 cells were examined. Three compounds, possessing two phenol units, were reported to inhibit the assembly of microtubule proteins and showed the inhibition of colony formation of V79 cells and increase in IL-8 production. Interestingly, a monomethoxy compound exhibited the stronger activity than the three active compounds in both bioassays. This compound did not inhibit the assembly of microtubule proteins. A dimethoxy compound was not active in either bioassays. In these experimental conditions, the biological activities were not high, but in future, these compounds will be expected to be made stronger by structural modifications.     

Seasonality of factors controlling N mineralization rates among slope positions and aspects in cool-temperate deciduous natural forests and larch plantations

This study aimed to evaluate the spatial patterns of soil nitrogen (N) transformations in relation to slope aspect and position, and to investigate the main factors controlling N transformation patterns during both the growing and dormant seasons in cool-temperate deciduous natural forests and larch plantations in eastern Hokkaido, northern Japan. Net rates of N mineralization (NR_minN) and of nitrification (NR_nit) in surface soils on north-facing and lower slopes were higher than those on south-facing and upper slopes, whereas the net rate of ammonium-N production (NR_amm) on south-facing and upper slopes was higher than that on north-facing slopes in both the natural forests and larch plantations. Both NR_minN and NR_nit were higher in the growing than in the dormant season, whereas NR_amm was higher in the dormant season. The soil C/N ratio, water content, soil pH and frequency of freeze–thaw cycles were important variables affecting N transformation patterns in any season. In relation to seasonality, the solar radiation index, daily temperature range and earthworm biomass were important controlling factors only during the growing season, and watershed area and soil N concentration only during the dormant season, suggesting that biological control accompanied with wet–dry events were important factors affecting N transformations during the growing season, but that run-off water and chemical controls were important determinants of spatial variation in N transformations during the dormant season.     

Inhibitory Effect of N,N-Didesmethylgrossularine-1 on Inflammatory Cytokine Production in Lipopolysaccharide-Stimulated RAW 264.7 Cells

N,N-Didesmethylgrossularine-1 (DDMG-1), a compound with a rare α-carboline structure, was isolated from an Indonesian ascidian Polycarpa aurata as responsible for the observed inhibitory activity against TNF-α production in lipopolysaccharide-stimulated murine macrophage-like RAW264.7 cells. DDMG-1 inhibited the mRNA level of mTNF-α, IκB-α degradation, and binding of NF-κB to the target DNA site in LPS-stimulated RAW 264.7 cells. Moreover, DDMG-1 had an inhibitory effect on the production of IL-8, which is produced in CD14⁺-THP-1 cells stimulated by LPS. DDMG-1 is thus a promising drug candidate lead compound for the treatment of chronic inflammatory diseases, such as rheumatoid arthritis.