Gross nitrification rates in four Japanese forest soils: heterotrophic versus autotrophic and the regulation factors for the nitrification

Measurements of gross NH ₄ ⁺ and NO ₃ ^? production in forest soils were conducted using the ¹⁵N pool dilution method. Mineral topsoils (0?C10?cm depth) were collected from four forests from northern to southern Japan with a natural climate gradient to elucidate the mechanisms regulating gross nitrification rates in forest soils. Additionally, we attempted to evaluate the relative importance of heterotrophic nitrification in gross total nitrification using acetylene as a specific inhibitor of autotrophic nitrification. Distinct differences were found among sites in the gross rates of NH ₄ ⁺ production (3.1?C11.4?mg?N?kg^?1?day^?1) and gross total nitrification (0.0?C6.1?mg?N?kg^?1?day^?1). The rates of gross heterotrophic nitrification were low in this study, indicating that heterotrophic nitrification is of minor importance in most forest mineral topsoils in Japan. Significant relations were found between gross autotrophic nitrification and gross NH ₄ ⁺ production, soil N, and soil C concentrations, but none was found between gross autotrophic nitrification and soil pH. We determined the critical value of the gross NH ₄ ⁺ production rates for gross autotrophic nitrification under which no gross autotrophic nitrification occurred, as well as the critical soil C/N ratio above which gross autotrophic nitrification ceased. Results show that tight coupling of production and consumption of NH ₄ ⁺ prevents autotrophic nitrifiers from utilizing NH ₄ ⁺ as long as NH ₄ ⁺ availability is low.     

Characterization of compounds that induce symbiosis between sea anemone and anemone fish

The species-specific partnership between the sea anemone and anemone fish in many parts of the Indo-Pacific region is a well-known phenomenon. Chemicals secreted by the sea anemone to elicit symbiotic behavior of the fish have been studied for two host-guest pairs, Radianthus kuekenthali (sea anemone)-Amphiprion perideraion (anemone fish) and Stoichactis kenti-A. ocellaris. A new pyridinium compound, amphikuemin, which induces characteristic attracted swimming (toward the chemical stimulus) in A. perideraion, has been isolated from R. kuekenthali and characterized. Several other chemicals that elicit characteristic symbiotic movements have also been identified.     

Soil Acidification and Decline of Trees in Forests Within the Precincts of Shrines in Kyoto (Japan)

The historical Japanese city of Kyoto boasts a great many old Buddhist temples and Shinto shrines, many of which are surrounded by sizable forests that have long been preserved as sacred forests. However, acidic deposition has been fallen on the forests in Kyoto for many years. For this study, we conducted soil surveys and investigated the extent of decline of the trees in two Shinto shrines as historic monuments of ancient Kyoto. Our study revealed clear decline in two key tree species (Cryptomeria japonica (Japanese cedar) and Chamaecyparis obtusa (Japanese cypress)) in both shrines, with some trees showing signs of mortality. The soil was acidic, with an average pH of 4.35. Nutrient salt content too was only about one tenth the national average, with exchangeable Ca (0.52 cequiv./kg) and Mg (0.23 cequiv./kg) for 0?C20 cm surface soil. The (Ca+Mg+K)/Al molar ratios were also very low, with 80% of all soil samples having a ratio of 10 or below. Such soil conditions are thought to hamper the sound growth of both Japanese cedar and Japanese cypress, and soil acidification is one of the most likely causes of the decline of temple and shrine forests in Kyoto.     

Regional differences in the phase velocity and the quality factor q of mantle rayleigh waves

The phase velocity and the quality factor (Q) of mantle Rayleigh waves from the great Kurile Islands earthquake of 1963 have a close azimuthal correlation with each other and differ considerably among different paths. Serious error may be introduced in the interpretation of observed regionality in phase velocity if regional differences in Q are ignored.     

Chemical characterization of a hormone that promotes cell arrest in g2 in complex tissues

A G(2|)factor in the cotyledons of Pisum sativum, which arrests the growth of cells in both roots and shoots in the G(2) stage of the cell cycle, has been isolated and identified as trigonelline (N-methylnicotinic acid). To our knowledge, trigonelline is the first hormone that effects cell arrest in complex tissues of plants and animals to be chemically identified.     

Visualization of 15O-water flow in tomato and rice in the light and dark using a positron-emitting tracer imaging system (PETIS)

Abstract

¹⁵P-water flow from the roots to the top in tomato (Lycopersicon esculentum Mill.) and rice (Oryza sativa L.) plants was visualized with time using a positron-emitting tracer imaging system (PETIS). The ¹⁵O-water flow was switched on by light and completely stopped in the dark. The flow rate in the stem of tomato and the shoot of rice at a light intensity of 500 μmol·m^?2·s^?1 was 1.9 and 0.4 cm min^?1, respectively.     

Directed evolution of yeast ferric reductase to produce plants with tolerance to iron deficiency in alkaline soils

One of the most serious problems in agriculture worldwide is low iron (Fe) availability, due to high soil pH. About 30% of arable land is too alkaline for optimal crop production. Non-graminaceous and dicot plants, which use a reduction strategy to uptake Fe, suffer from Fe deficiency under these conditions, because the ferric chalets reductase in the root plasma membrane functions inefficiently at high pH. The refrel (reconstructed yeast ferric reductase) gene was subjected to random mutagenesis to obtain variants with high activity under high pH conditions. A mutant library was screened using a yeast in vivo assay system, and screens at pH 8.0 and 8.5 produced 10 candidates. In vivo ferric reductase activity was analyzed quantitatively. Yeast cells carrying the variant with the highest ferric reductase activity showed 6.0, 8.7, and 38 times greater activity at pH 8.0, 8.5, and 9.0, respectively, than did cells containing the original refrel gene. An amino acid substitution at position 312 was common to most of the high-activity variants. This substitution is believed to play an important role in the increased reductase activity at high pH. Interestingly, this mutation is near a hams-coordinating histidine co on, and the corresponding residue is probably located in the intramembranous region close to the cytoplasm. The variant gene with the highest reductase activity was introduced into tobacco, and transgenic tobacco carrying the gene showed enhanced tolerance to low Fe availability. This result should be useful in the engineering of non-graminaceous and dicot plants tolerant to Fe deficiency in alkaline soils.     

Survival,growth and fertility of gynogenetic diploids induced in the cyprinid loach, Misgurnus anguillicaudatus

Gynogenetic diploids were induced in the loach, Misgurnus anguillicaudatus, by applying cold shock to the egg after fertilization with spermatozoa genetically inactivated by ultraviolet-ray irradiation, to examine their survival, growth and fertility. Eggs were obtained from orange phenotype loach (homozygous for a recessive demelanogenesis gene). Spermatozoa were obtained from black phenotype loach (homozygous for a dominant melanogenesis gene), and from common carp, Cyprinus carpio. All hybrids between loach and carp were inviably abnormal.Eggs fertilized with loach or carp spermatozoa irradiated at doses of 6000 and 12000 erg/mm ² and then treated with cold water (1°C for one hour 4 and 5 min after fertilization developed into embryos with 61–78% survival. About 70–87% of newly-hatched fry were normal in appearance. Gynogenetic fish induced by both loach and carp spermatozoa showed lower rates of survival and growth than did the normal diploid controls. All gynogenetic fish from carp spermatozoa were female and 94.9% of the gynogenetic fish from loach spermatozoa were female. The second gynogenetic offsprings were produced from females selected from both gynogenetic groups.     

Modified resazurin microtiter assay for in vitro and in vivo assessment of sulfamonomethoxine activity against the fish pathogen <Emphasis Type="Italic">Nocardia seriolae</Emphasis>

Resazurin microtiter assay (REMA) was carried out using four sulfonamides, three culture media, and four inoculum sizes as a first screening step to establish an easy-to-interpret sulfonamides susceptibility testing method for Nocardia seriolae. The in vitro activity of sulfamonomethoxine (SMM) against 190 clinical N. seriolae isolates was then examined, and in vivo experimental treatment was performed. When the culture medium and the inoculum size were considered in tandem, a 0.5× the original concentration of cation-adjusted Mueller–Hinton broth and an inoculum size of 10² CFU/well showed the clearest endpoint reading for all tested drugs, and the REMA-generated data were in excellent agreement with those generated by the reference Etest method. SMM activity showed minimum inhibitory concentration (MIC) values of 4–32 μg/ml against all tested N. seriolae isolates. Treatment of amberjack groups experimentally infected with N. seriolae isolates having SMM MICs of 4 and 32 μg/ml, resulted in survival rates of 100% and 87.5% in the two groups, respectively. In this study, we developed a simple visual method to test SMM activity against N. seriolae.