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1.  Morning reduction of photosynthetic capacity before midday depression 
Scientific Reports  2014;4:4389.
Midday depression of photosynthesis has important consequences for ecosystem carbon exchange. Recent studies of forest trees have demonstrated that latent reduction of photosynthetic capacity can begin in the early morning, preceding the midday depression. We investigated whether such early morning reduction also occurs in an herbaceous species, Oenothera biennis. Diurnal changes of the photosynthetic light response curve (measured using a light-emitting diode) and incident sunlight intensity were measured under field conditions. The following results were obtained: (1) the light-saturated photosynthetic rate decreased beginning at sunrise; (2) the incident sunlight intensity on the leaves increased from sunrise; and (3) combining (1) and (2), the net photosynthetic rate under natural sunlight intensity increased from sunrise, reached a maximum at mid-morning, and then showed midday depression. Our results demonstrate that the latent morning reduction of photosynthetic capacity begins at sunrise, preceding the apparent midday depression, in agreement with previous studies of forest trees.
PMCID: PMC3955906  PMID: 24633128
2.  Combined Analyses of Bacterial, Fungal and Nematode Communities in Andosolic Agricultural Soils in Japan 
Microbes and Environments  2012;27(1):72-79.
We simultaneously examined the bacteria, fungi and nematode communities in Andosols from four agro-geographical sites in Japan using polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE) and statistical analyses to test the effects of environmental factors including soil properties on these communities depending on geographical sites. Statistical analyses such as Principal component analysis (PCA) and Redundancy analysis (RDA) revealed that the compositions of the three soil biota communities were strongly affected by geographical sites, which were in turn strongly associated with soil characteristics such as total C (TC), total N (TN), C/N ratio and annual mean soil temperature (ST). In particular, the TC, TN and C/N ratio had stronger effects on bacterial and fungal communities than on the nematode community. Additionally, two-way cluster analysis using the combined DGGE profile also indicated that all soil samples were classified into four clusters corresponding to the four sites, showing high site specificity of soil samples, and all DNA bands were classified into four clusters, showing the coexistence of specific DGGE bands of bacteria, fungi and nematodes in Andosol fields. The results of this study suggest that geography relative to soil properties has a simultaneous impact on soil microbial and nematode community compositions. This is the first combined profile analysis of bacteria, fungi and nematodes at different sites with agricultural Andosols.
PMCID: PMC4036027  PMID: 22223474
bacteria-fungi-nematode community; andosols; PCR-DGGE; two-way cluster analysis
3.  Effect of Storage Temperature on Soil Nematode Community Structures as Revealed by PCR-DGGE 
Journal of Nematology  2010;42(4):324-331.
The optimal duration and conditions for storage of soils collected for nematode community analyses are unknown. To study this issue, three types of soils with different geographical origins from the subarctic to cool-temperate Japan were kept at three temperature levels (5, 10, and 20°C) for up to 8 wk following collection. During the storage period, nematode population density was measured, and community structure was assessed by polymerase chain reaction denaturing gradient gel electrophoresis (PCR-DGGE). No significant changes in the population density or diversity of nematodes (Shannon-Wiener Diversity Index) were observed during storage compared to initial states, except that density in an andosol collected from Tsukuba, Central Japan decreased significantly after 28 d of storage at 5°C. However, a regression analysis showed a declining trend in nematode density in the latter half of the storage period when soils were stored at 5 or 20°C, depending on the geographic origin of the soil. These results indicate that soils can be stored for 14 d at 5–20°C, with 10°C as optimal. This is the first study to experimentally determine the optimal preservation conditions for nematode assemblages in soils that are to be analyzed using PCR-DGGE.
PMCID: PMC3380525  PMID: 22736866
biodiversity; ecology; method; soil fauna
4.  Comparative Studies between Portuguese and Japanese Isolates of the Pinewood Nematode, Bursaphelenchus xylophilus  
Journal of nematology  2006;38(4):429-433.
Comparative studies between Portuguese (T and HF) and Japanese (S10, T4, C14-5 and OKD-1) isolates of the pinewood nematode Bursaphelenchus xylophilus have been made in order to provide information to better understand the possible origin of the Portuguese isolates, recently introduced in the European Union. The main comparative aspects investigated were pathogenicity (seedling mortality ratio), sexual compatibility, and DNA sequences of the rDNA region. Four-year-old Japanese black pine (Pinus thunbergii) seedlings were used as host plants for pathogenicity tests. The Portuguese isolates, and in particular isolate “T,” propagated in higher numbers than the Japanese isolates within pine seedlings. All combinations of crossings produced viable progeny, with higher numbers obtained when crossings were made between Japanese and Portuguese isolates, a possible situation of heterosis and/or inbreeding depression. Reciprocal crossings yielded different values, which may reflect a sex effect (maternal inheritance, mtDNA). Regarding DNA sequencing, both Portuguese isolates displayed nearly identical ITS 1, ITS2, and 5.8S rDNA base sequences as the Japanese isolates. Although biologically very similar, and possibly reflecting a common origin, the Portuguese isolates may present a serious threat to Japanese black pine, due to their higher virulence.
PMCID: PMC2586472  PMID: 19259459
Portugal; Japan; pathogenicity; sexual compatibility; DNA sequence

Results 1-4 (4)