Temperature sensitivity of soil CO2 production in a tropical hill evergreen forest in northern Thailand

Tropical forests, like boreal forests, are considered key ecosystems with regard to climate change. The temperature sensitivity of soil CO₂ production in tropical forests is unclear, especially in eastern Asia, because of a lack of data. The year-round variation in temperature is very small in tropical forests such that it is difficult to evaluate the temperature sensitivity of soil CO₂ production using field observations, unlike the conditions that occur in temperate and boreal forests. This study examined the temperature sensitivity of soil CO₂ production in the tropical hill evergreen forest that covers northern Thailand, Laos, and Myanmar; this forest has small temperature seasonality. Using an undisturbed soil sample (0.2 m diameter, 0.4 m long), CO₂ production rates were measured at three different temperatures. The CO₂ production (SR, mg CO₂ m⁻² s⁻¹) increased exponentially with temperature (T, °C); the fitted curve was SR = 0.023 e^0.077T, with Q₁₀ = 2.2. Although still limited, our result supports the possibility that even a small increase in the temperature of this region might accelerate carbon release because of the exponential sensitivity and high average temperature.     

Effect of electric impulse on sporocarp formation of ectomycorrhizal fungusLaccaria laccata in Japanese red pine plantation

We examined the effect of electric impulses on sporocarp formations of ectomycorrhizal fungus in a Japanese red pine (Pinus densiflora) plantation.Laccaria laccata was the dominant species in this study plantation. Spatial distribution concentrated in the electric impulse treatment zone, and recorded a markedly larger number of sporocarps compared with untreated control plots. The effect of electric impulses was also recognized onL. laccata fruiting with a mycorrhizal sapling in a pot. Sporocarp production ofL. laccata was strongly promoted by the electric impulse in experiments bothin vivo natural plantation stands andin vitro pot saplings. Our work indicates the possibility of enhancement of sporocarp production of the mycorrhizal fungi with electric impulses in the nursery and plantation. This work was partly supported by a grant from the Kyushu Electric Power Company.     

Cultivation of <Emphasis Type="Italic">Pleurotus eryngii</Emphasis> on umbrella plant (<Emphasis Type="Italic">Cyperus alternifolius</Emphasis>) substrate

Mycelial growth and mushroom yields of three strains of Pleurotus eryngii produced on wheat bran-supplemented umbrella plant (Cyperus alternifolius) substrate were assessed using surface brightness, bromophenol blue color reactions, ergosterol and glucosamine contents, and water potential as indicators of strain performance. Mycelial growth was 31%–46% greater, depending on strain, on the umbrella plant substrate compared with the mushroom industry standard sugi (Cryptomeria japonica) substrate. Mushroom yields on the first flush were 20%–23% higher, depending on strain, on the plastic bottle-contained umbrella plant substrate. However, yields on the second break were lower from the umbrella plant substrate. Because many growers in Japan only harvest one flush, production of P. eryngii on umbrella plant substrate may offer commercial producers an alternative basal ingredient to diminishing supplies of sugi sawdust.Part of this report was presented at the 52nd Annual Meeting of the Japan Wood Research Society, Gifu, April 2002.     

Histological studies of shoot regeneration system in hypocotyl-derived callus of Phellodendron amurense Rupr.

An efficient in vitro plant regeneration was achieved from hypocotyl-derived callus of a medicinal tree Phellodendron amurense. The expected morphogenic response was obtained on the media containing 0.89 µM 6-benzyl aminopurine (BAP) plus 4.52 µM 2.4-dichlorophenoxyacetic acid (2,4-D), 4.44 µM BAP plus 5.37 µM α-naphthaleneacetic acid (NAA), or 2.22 µM BAP plus 4.92 µM indole-3-butyric acid (IBA). A detailed histological study was undertaken to gain a better understanding of cellular changes that take place during the plant regeneration process from callus tissue. This study led to the identification of the cellular origin of shoot regeneration. Histological studies revealed that the new vegetative buds originated from callus that completely altered the morphology of the callus tissues by the 60th day of culture. It also revealed that BAP with NAA or IBA induces plant regeneration through organogenesis whereas BAP with 2,4-D induces embryo-like-structure (ELS) through hypocotyl-derived callus. The presence of ELS lacking root poles was also observed.     

Rainfall-runoff responses and roles of soil moisture variations to the response in tropical rain forest, bukit tarek, peninsular Malaysia

Field observations were conducted at Bukit Tarek Experimental Watershed in Peninsular Malaysia to investigate the relationship between rainfall-runoff responses and variation in soil moisture in a tropical rain forest. Stormflow depended strongly on the antecedent wetness as represented by the initial runoff rate. Though heavy rains fell in almost every month, the soil moisture decreased when fair weather was sustained. The soil moisture depleted and became dry at 160 cm depth during occasional dry spells. During dry conditions, streamflow responded quickly to rain events but declined rapidly after the rain stopped, and the soil moisture of surface soil (≤20 cm) increased but remained dry at lower depths (≽80 cm). This suggests that the rain water was mostly retained in the soil and only small proportions appeared as stormflow. As soil moisture conditions became wetter, the recession limb of the storm hydrograph was more gradual. Stormflow volume increased with increasing soil moisture. During wet conditions, the soil profile was moist at all parts of the slope. The hydraulic gradient was around 1.0 and there was downward soil water flux, which followed the pressure gradient. This suggests that subsurface flow from the upper part of the slope might also be important for stream-flow production. Positive pressures were observed at 10 cm and 160 cm depths during large storms. The behavior of the subsurface flow might be an important determinant of stormflow.     

Soil respiration and soil CO<Subscript>2</Subscript> concentration in a tropical forest,Thailand

Soil respiration and soil carbon dioxide (CO₂) concentration were investigated in a tropical monsoon forest in northern Thailand, from 1998 to 2000. Soil respiration was relatively high during the rainy season and low during the dry season, although interannual fluctuations were large. Soil moisture was widely different between the dry and wet seasons, while soil temperature changed little throughout the year. As a result, the rate of soil respiration is determined predominantly by soil moisture, not by soil temperature. The roughly estimated annual soil respiration rate was 2560gCm^–2year^–1. The soil CO₂ concentration also increased in the rainy season and decreased in the dry season, and showed clearer seasonality than soil respiration did.     

Development of an in vitro model for the analysis of bovine endometrium using simple techniques

This study aimed to develop an in vitro model for the analysis of the bovine endometrium. Immunofluorescent staining revealed that the hetero‐spheroids and the cultured explants showed almost similar structure in the localization of bovine endometrial epithelial cells and endometrial stromal cells, except the glandular‐like structure of the epithelial cells inside the explants. Gelatin zymography revealed that the hetero‐spheroids did not express matrix metalloproteinases (MMPs) after 4 days of culture, but strong MMP expressions were observed in the cultured explants until 7 days of culture. Additionally, expression of progesterone receptor (PR), estrogen receptor alpha (ERα), type I interferon receptor 1 (IFNAR1) and 2 (IFNAR2) messenger RNA was observed both in the homo‐ and hetero‐spheroids. The expression of oxytocin receptor (OTR) mRNA in E2 and E2+P4 (1,3,5(10)‐Estratrien‐3, 17β‐diol + 4‐Pregnen‐3, 20‐dinone) treated groups were significantly (P < 0.05) higher than that of the control group of spheroids. In case of cultured explants, the expression of PR and OTR mRNA were significantly (P < 0.05) higher in E2 treated groups compared to the control groups. Hepatocyte growth factor (HGF) mRNA expression was also higher in P4 treated groups at 10 days in culture (P < 0.05). In a nutshell, the in vitro model developed in this study for the analysis of the endometrium may provide a new platform for extensive research on bovine endometrial function.     

Preincubation with green tea polyphenol extract is beneficial for attenuating sperm injury caused by freezing‐thawing in swine

Polyphenols (PFs) extracted from green tea, known to be potent anti‐oxidants, have been reported to be effective in increasing the motility and viability of mammalian sperm, preserved in a liquid form. Therefore, we tested whether PFs might also be effective for maintaining the integrity of frozen‐thawed boar spermatozoa. Ejaculates, collected from Clawn miniature pigs, were diluted in a semen extender containing various amounts of PFs (0, 0.01, 0.05, 0.1 and 0.2% w/v) and then stored at 15°C overnight. The semen samples were processed, using the straw freezing procedure, and then frozen in liquid nitrogen. After rapid thawing at 40°C, the spermatozoa were subjected to several assays to evaluate semen quality. Spermatozoa frozen in a medium containing 0.01% w/v PFs exhibited significantly (P < 0.05) higher degrees of post‐thawed viability and acrosomal integrity than those stored in the absence of PFs. However, no change in the mitochondrial activity was noted between the two groups. The inclusion of 0.01% PFs in the semen extender was significantly (P < 0.05) effective in increasing both the rates of monospermic oocyte formation and of blastocyst formation. These findings indicate that preincubation with the semen extender, containing 0.01% PFs prior to freezing, exerts a protective effect on boar sperm by preventing injuries associated with freezing‐thawing.     

A new rolling culture‐based in vitro fertilization system capable of reducing polyspermy in porcine oocytes

The high incidence of polyspermy is one of the major obstacles during in vitro fertilization (IVF) in pigs. To overcome this, we developed a novel IVF method, which involves constant rotation. Oocytes matured in vitro were mixed with spermatozoa (0.2 × 10⁵ sperm/mL) in an IVF medium (200 μL) using a 200 μL PCR tube. This tube was then rotated at 1 rpm for 6 h at 38.5°C in a rotation mixer (experimental group). A second PCR tube was simultaneously cultured without rotation (control group). The rate of polyspermy was evaluated 12 h after insemination and was significantly (P < 0.05; 21.0% vs. 48.3%) lower in the experimental group than in the control group. Sperm penetration rate was similar in oocytes from the experimental and control groups (75.2% vs. 83.1%). However, monospermic fertilization rate of the oocytes was significantly (P < 0.05; 44.8% vs. 21.2%) higher in the experimental group than in the control group. Furthermore, the rate of blastocyst formation (30.1% vs. 20.8%) increased in the experimental group, as compared to the control group. This present system will contribute to increase the efficacy of blastocyst production through reduction of polyspermic penetration.     

Stimulatory effect of plasma samples from fattening cattle on adipogenesis‐related gene expression in preadipocyte cells

It is desirable to produce beef with high levels of monounsaturated fatty acids (MUFA), as this is related to fat softness and palatability. However, the physiology of MUFA synthesis in bovine fat during the fattening process remains to be established. In this study, in order to elucidate the relationship between plasma components and the fatty acid composition of intramuscular fat, we investigated the effect of plasma obtained from fattening cattle on the messenger RNA (mRNA) expressions of the adipogenesis‐related gene in a clonal bovine intramuscular preadipocyte line (BIP cells). The mRNA expressions of stearoyl‐CoA desaturase, adipocyte Protein 2, peroxisome proliferator‐activated receptor gamma and sterol regulatory element‐binding protein 1 in BIP cells were significantly higher following treatment with those plasma samples collected from the cattle with the highest diaphragmatic unsaturated fatty acids to saturated fatty acids ratio (US/S). Furthermore, the concentration of nonesterified fatty acid (NEFA) in the plasma samples had an inverse correlation with carcass diaphragmatic US/S. These results indicate that cattle with a low ratio of US/S in fat may be discriminated from the population of fattening cattle before slaughter by measuring the effect of their plasma on gene expression in BIP cells as well as their plasma concentration and composition of NEFA.