Effects of chronic acid fog exposure with soil acidification or nitrogen loading on nutrient status in Abies firma seedlings

To clarify the nutrient status in momi fir (Abies firma Sieb. et Zucc.) seedlings under complex stress conditions of acid fog with soil acidification or nitrogen loading, we exposed seedling shoots to simulated acid fog (pH 3) and simultaneously loaded the soil with acid or excess nitrogen for 17 months. Proton and nitrogen loading reduced K concentration in soil, but these treatments had little effect on the nutrient status of fine roots in momi fir seedlings. Acid fog exposure resulted in reduced concentrations of Mg, Al, and Fe in current-year needles and Mg, Al, Cu, Fe, and Zn in 1-year-old needles. The complex effects of acid fog exposure with proton or nitrogen loading on nutrient status were relatively slight. However, elements such as Al and Cu notably reflect the effects of proton loading. These results show that the nutrient status of trace elements, rather than major elements, in needles of momi fir seedlings is sensitive to exposure to acid fog or proton loading.     

The effect of strain, growth stage, and cultivating condition of Ganoderma lucidum on 5α-reductase inhibition

The inhibitory effects of 102 methanol extracts of 40 mycelia, 9 culture fluids, and 53 fruiting bodies of 40 strains of Ganoderma lucidum on 5-reductase were investigated. The methanol extract of the fruiting body of each strain was found to show the strongest 5-reductase inhibitory activity among the extracts tested.     

Structure of xylan from culms of bamboo grass (Sasa senanensis Rehd.)

Xylan prepared from culms of kumaizasa (Sasa senanensis Rehd.), a representative species of bamboo grass, was hydrolyzed with-xylanase ofStreptomyces olivaceoviridis E-86. Four arabinoxylo-oligosaccharides and two glucuronoxylo-oligosaccharides were isolated from the enzymatic hydrolysate of the xylan by chromatography on a charcoal column, a Dowex 1-x8 column, a Toyo-pearl HW-40S column, and a LiChrospher 100 NH₂ column and on preparative paper chromatography. The results of the structural analyses of the saccharides showed that the isolated oligosaccharides had the structures of 3²--l-arabinofuranosyl-xylobiose, 3²--l-arabinofuranosyl-xylotriose, 3²--[-d-xylopyranosyl-(1 2)-l-arabinofuranosyl]-xylobiose, 3³--[-d-xylopyranosyl-(1 2)-l-arabinofuranosyl]-xylotriose, 2³--4-O-methyl-d-glucuronosyl-xylotriose, and 2³--d-glucuronosyl-xylotriose. From the structural analysis of the oligosaccharides derived from the xylan, kumaizasa xylan was concluded to be a kind of arabinoglucuronoxylan having not only stubs of singlel-arabinose and singled-glucuronic acid but also stubs of disaccharide units such as-d-xylopyranosyl-(1 2)-l-arabinofuranose.     

Generation and alteration of norlignans in a transition zone during the drying of a Cryptomeria japonica log

Sugi (Cryptomeria japonica D. Don) produces secondary metabolite norlignans in xylem. Several norlignans are involved in the coloration of heartwood and defense of sapwood against microbial invasion. Their biosynthetic process should be well understood so that their properties can be exploited to improve the quality and utility of C. japonica wood. Unfortunately, information on the norlignan biosynthesis is limited because norlignans are mainly synthesized in a particular season in the transition zone (TZ) along with the heartwood formation, and is difficult to study. Although the generation of two norlignans of C. japonica, agatharesinol and (E)-hinokiresinol, has been reported, systems for producing other norlignans are not yet known. To establish a novel norlignan generating system, we examined the changes occurring in norlignans in a TZ during the process of drying a C. japonica log. On the day of felling, the TZ contained agatharesinol and (E)-hinokiresinol, which increased until they reached a maximum on day 40 after felling. Sequirin-C appeared on day 40 and increased to day 70. The generation of sequirin-C in the TZ can be used to investigate the biosynthetic process of heartwood norlignans. This study describes for the first time the changes that occur in the composition of norlignan during the drying of the TZ.     

Allometric model of the height–diameter curve for even-aged pure stands of Japanese cedar (<Emphasis Type="Italic">Cryptomeria japonica</Emphasis>)

We derived an allometric model of the height–diameter curve for even-aged pure stands, which was a modification of the earlier model proposed by Inoue (2000a). An individual-dependent allometric equation was used as the height–diameter curve. Using the discriminant analysis method, all trees composed of a stand were stratified into upper and lower trees. It was assumed that both relationships between mean tree height H _m and upper tree height H _u and between mean DBH D _m and mean DBH of upper trees D _u could be described by the time-dependent allometric power equations. The height–diameter curve showed an average relationship between tree height and DBH of a given stand at a given time, and hence it could be assumed that the height–diameter curve contained two points (D _m , H _m ) and (D _u , H _u ). With these assumptions, we derived an allometirc model of height–diameter curve, which allowed the coefficients of the curve to be estimated from mean tree height and mean DBH. The proposed model was fitted to Japanese cedar (Cryptomeria japonica D. Don) data. The error ratio of the allometric model ranged from 2.254% to 13.412% (mean = 6.785%), which was significantly smaller than that of the earlier model. When the error of mean tree height was ±1.0 m or less, the effect of the error of mean tree height on the error ratio was comparatively small. This suggested that the error of ±1.0 m in mean tree height could be accepted in the estimation of height–diameter curve using the allometric model. These features enable us to combine the allometric model with Hirata’s vertical angle-count sampling or growth models. In conclusion, the allometric model would be one of the most practical and convenient approaches for estimating the height–diameter relationship of even-aged pure stands.     

Importance of rubberwood in wood export of Malaysia and Thailand

We examined the contribution of rubberwood to the timber export markets of Malaysia and Thailand. In Malaysia, rubberwood has grown from 26% of total exported wood products in 1998 to 35% in 2007. A high proportion of furniture products (80%) is rubberwood, whereas the contribution of rubberwood to other wooden products is less than 20%. Only 10% of sawn timber and logs is rubberwood. In Thailand, rubberwood contributes to around 60% of total exported wood products, arising from a high share of not only furniture products (70%) but also other wood products (around 50%) and sawn timber and logs, which have increased in share from 40% in 1998 to 79% in 2007. We conclude that the high proportion of rubberwood products in the wood export markets of these two countries is a result of: (1) scarcity of raw wood materials because of strict controls on the logging of natural forests; and (2) governmental support to rubberwood production, including financial support to rubber planters and technical assistance to downstream timber processors.     

Iodine desorption from rice paddy soil

Laboratory experiments on the desorption phenomena of iodine from rice paddy soil under waterlogged conditions, with a special reference to soil redox potential (Eh) and pH, have been conducted. Radioiodine tracer (1251), added to the soil, was readily sorbed on it. At the beginning of the waterlogging, the iodine desorption was low. However, iodine was desorbed into soil solution with time. The iodine desorption was enhanced markedly by the addition of organic substances such as straw pieces and glucose to the soil. Cultivation of rice plants in soil also affected the iodine desorption, suggesting root exudates and/or root autolysis might be participating in the desorption process. Eh dropped considerably after soil was waterlogged due to microbial metabolisms. Particularly low Eh values were observed in soils with plants and also with added organic substances. A negative correlation was seen between the desorption and soil Eh. High desorption was frequently observed when the Eh dropped to about -100 mV or below. Due to the reducing conditions (low Eh) by waterlogging, iodine in soil was leached into the soil solution; consequently total iodine concentration in paddy soil was considerably lower than forest and upland field soils. These iodine desorption phenomena under anaerobic conditions should be considered in assessing transfer of the long-lived radioiodine (129I) in the environment, especially in rice fields and marshland.     

Protozoan predation of Escherichia coli in hydroponic media of leafy vegetables

Multiple outbreaks of food poisoning associated with fresh vegetable consumptions have occurred in many countries. Numerous reports have described human pathogenic bacteria, such as Escherichia coli O157:H7 and Salmonella spp., that can internalize into fresh vegetables via root or leaf surfaces. While attempting to obtain the threshold concentration of internalization of E. coli inoculated into hydroponic medium during vegetable cultivation, we observed a rapid decrease in E. coli numbers. In the present study, we determined that the rapid decline in E. coli was not due to a physiological change into a viable but non-culturable (VNC) state. The population crash was instead caused by true bacterial death, as the rapid descent was also confirmed by micro-colony fluorescence in situ hybridization, a culture-independent method that can detect VNC cells. We next monitored the number of E. coli inoculated into intact or filter-sterilized hydroponic medium after cultivation of various types of plants. We found that the number of E. coli in intact hydroponic medium decreased markedly, whereas the level in filter-sterilized hydroponic medium was completely unchanged. This result suggests that biotic factors were present that could be eliminated by filtering. Robust predation of E. coli by protozoa (ciliates and flagellates) was observed using fluorescently labeled bacteria incorporated into the hydroponic medium. Finally, morphological identification of flagellates by scanning electron microscopy revealed the presence of a species of Stramenopiles. These findings suggest the importance of protozoa as bacterial feeders in hydroponic systems and hence the use of these organisms as potential control agents of human pathogenic bacteria.     

Reduced immunogenicity of beta-lactoglobulin by conjugation with carboxymethyl dextran differing in molecular weight

To reduce the immunogenicity of beta-lactoglobulin (beta-LG), two beta-LG-carboxymethyl dextran (CMD) conjugates (Conj. 40 and Conj. 162) were prepared by using water-soluble carbodiimide (EDC). The molar ratios of beta-LG to CMD in Conj. 40 and Conj. 162 were 8:1 and 7:1, respectively. Each conjugate maintained approximately 50% of the retinol binding activity of beta-LG. Structural analyses by intrinsic fluorescence, CD spectra, and ELISA with monoclonal antibodies indicated that the surface of beta-LG in each conjugate was covered by CMD without great disruption of native conformation. By conjugation with CMD, the antibody response to beta-LG was reduced in BALB/c, C3H/He, and C57BL/6 mice, which was eminent in Conj. 162. The results of B cell epitope scanning using overlapping synthesized peptides showed that the linear epitope profiles of the conjugates were similar to those of beta-LG, whereas the antibody response to each epitope was reduced, which was eminent in Conj. 162. It was concluded that conjugation with CMD of higher molecular weight is effective in reducing the immunogenicity of beta-LG and that masking of epitopes by CMD is responsible for the reduced immunogenicity.