Epibiotic bacteria associated with microcrustaceans in the overlying water of paddy fields

The surface of micro crustaceans collected from the overlying water of a submerged paddy soil was observed in detail by scanning electron microscopy. Epibiotic bacteria were less diverse compared to free-living bacteria in the overlying water. Specific bacteria appeared to preferentially colonize certain parts of microcrustaceans. The epibiotic bacteria, the sites they colonized and their density depended on the kinds of microcrustaceans (Moina macrocopa, Cyclopidae, Cypretta sp., and Tanycypris sp.). These results suggested the presence of significant associations in the overlying water between specific groups of bacteria and microcrustaceans.     

Effects of successive soil freeze-thaw cycles on soil microbial biomass and organic matter decomposition potential of soils

Abstract

Effects of soil freeze-thaw cycles on soil microbial biomass were examined using 8 soil samples collected from various locations, including 4 arable land sites and 2 forest sites in temperate regions and 2 arable land sites in tropical regions. The amounts of soil microbial biomass C and N, determined by the chloroform fumigation and extraction method, significantly decreased by 6 to 40% following four successive soil freeze-thaw cycles (- 13 and 4°C at 12 h-intervals) compared with the unfrozen control (kept at 4°C during the same period of time as that of the freeze-thaw cycles). In other words, it was suggested that 60 to 94% of the soil microorganisms might survive following the successive freeze-thaw cycles. Canonical correlation analysis revealed a significantly positive correlation between the rate of microbial survival and organic matter content of soil (r = 0.948*). Correlation analysis showed that the microbial survival rate was also positively correlated with the pore-space whose size ranged from 9.5 to 6.0 μm (capillary-equivalent-diameter; r = 0.995**), pH(KCI) values (r = 0.925**), EC values (r = 0.855*), and pH (H₂O) values (r = 0.778*), respectively. These results suggested that the soil physicochemical properties regulating the amount of unfrozen water in soil may affect the rate of microbial survival following the soil freeze-thaw cycles. The potential of organic matter decomposition of the soils was examined to estimate the effects of the soil freeze-thaw cycles on the soil processes associated with the soil microbial communities. The soil freeze-thaw cycles led to significant 6% increase in chitin decomposition and 7% decrease in rice straw decomposition (p < 0.05), suggesting that the partial sterilization associated with the soil freeze-thaw cycles might disturb the soil microbial functions.     

Estrous cycle based on blood progesterone profiles and changes in vulvar appearance of Malayan tapirs (Tapirus indicus)

The progesterone (P(4)) profiles and macroscopic vulvar changes of female Malayan tapirs were investigated in order to understand their fundamental reproductive physiology and to search for visual indicators of estrus. Blood was collected once or twice a week from seven female Malayan tapirs kept at four zoos. Serum or plasma P(4) concentrations were determined by radioimmunoassay. The P(4) concentrations changed cyclically throughout the years, and a total of 56 cycles was confirmed in the seven females. The length of the estrous cycle based on the P(4) profiles was 43.6+/-2.0 days; however, this mean includes great variation in length, from 21 to 84 days. Mucous discharge from the vulva and vulvar swelling were seen when the P(4) concentrations were low before the beginning of a rise in most cases. In conclusion, captive female Malayan tapirs have variations of approximately 1 to 3 months in estrous cycle length, and visual changes in the vulva are helpful in estimating estrus in female Malayan tapirs.     

Factor analysis of risk-taking behavior in forest work

In this study, the data obtained by a questionnaire survey were analyzed to examine the difference with the type of occupation, consistency in each situation, the inductive and restraint factors of the risk-taking behavior in the forest work to elucidate the risk-taking behavior in forest work. The results showed that (1) the Kyushu Forest Cooperative Association’s staff members underestimate the risk, but have a strong recognition of “law observance,” (2) the supervisor or instructor has low consciousness of risk, (3) as the inductive factor of behavior, one’s own benefit in the daily situation is given the highest priority, but risk is the most important factor in situations concerning forest work and forest machine operation and handling, irrespective of the accuracy of the risk evaluation, (4) as the restraint factor of behavior, although there is a difference in the risk evaluation whether large or small, risk is given priority by all workers, and (5) the dare probability of each risk-taking behavior is highly correlated with the risk evaluation of the behavior. Among others, low consciousness of the supervisor or instructor concerning safety management is pointed out as a main factor in worker’s accidents, and reconsideration of the relationship between the supervisor or instructor and workers is necessary.     

Effects of erect panicle genotype and environment interactions on rice yield and yield components

The dense and erect panicle (EP) genotype conferred by DEP1 has been widely used in the breeding of high-yield Chinese japonica rice varieties.  However, the breeding value of the EP genotype has rarely been determined at the plant population level.  Therefore, the effects of the interaction of EP genotype and the environment at different locations and times on rice yield and its various components were investigated in this study.  Two sets of near-isogenic lines (NILs) of EP and non-EP (NEP) genotypes with Liaojing 5 (LG5) and Akitakomachi (AKI) backgrounds were grown in the field in 2016 and 2017 in Shenyang, China, and Kyoto, Japan.  In 2018, these sets were grown only in Kyoto, Japan.  The average yields of the EP and NEP genotypes were 6.67 and 6.13 t ha⁻¹ for the AKI background, and 6.66 and 6.58 t ha⁻¹ for the LG5 background, respectively.  The EP genotype positively affected panicle number (PN) and grain number per square meter (GNPM), mostly resulting in a positive effect on harvest index (HI).  In contrast, the EP genotype exerted a negative effect on thousand-grain weight (KGW).  The ratio of the performance of the EP genotype relative to the NEP genotype in terms of yield and total biomass correlated positively with mean daily solar radiation during a 40-day period around heading.  These results indicate that the effectiveness of the EP genotype depends on the availability of solar radiation, and the effect of this genotype is consistently positive for sink formation, conditional in terms of source capacity, and positive in a high-radiation environment.     

Low nitrogen availability and shallow plow layer decrease sugarcane (Saccharum officinarum L.) productivity in Kitadaito Island,Japan

Sugarcane is the main crop in Kitadaito Island, Okinawa, Japan. The average yield in Kitadaito Island for the past 30 years (1985–2015) was 44 Mg ha^?1, 31% lower than that (64 Mg ha^?1) in Okinawa Prefecture. Among the reasons for the low sugarcane productivity in Kitadaito Island, the effects of soil and cultivation factors have not been sufficiently studied. The objectives of this study were i) to evaluate the effects of soil physical and chemical properties and cultivation factors on sugarcane yield and sugar content in 50 fields of Kitadaito Island, and ii) to clarify factors affecting the sugarcane yield and sugar content. Statistical analysis of classification and regression trees (CART) showed that the sugarcane yield was low in fields with low available nitrogen (less than 16.5 mg kg^?1) and with shallow plow layer depth (less than 29 cm). The soil available nitrogen had a significant positive correlation with soil humus (r = 0.39, P < 0.05). Two-times of subsoiling in the field before planting and during growing periods resulted in the significant increase of the depth of plow layer, compared to the fields with single and no subsoiling. A high sugar content was obtained in fields with exchangeable Mg more than 3.8 cmol_c kg^?1 and pH(H₂O) less than 7.2. Our study therefore concluded that soil management practices for sugarcane production in Kitadaito Island should primarily be focused on available nitrogen, plow layer depth, and soil exchangeable Mg and pH.     

Plant development and yield components under a tropical environment in soybean cultivars with temperate and tropical origins

Cultivar tests under tropical environments could be an approach to explore soybean productivity under high temperature. Twenty-nine soybean cultivars divided into five groups with temperate origin (Japanese and US) and tropical origin (Indonesian-old, Indonesian-modern and other tropical) were grown for two years in a tropical environment at Banten, Indonesia, with minimal season-to-season variation in air temperature and day-length. Temperate cultivars were earlier in flowering and shorter in duration from R1 to R5. Temperate cultivars had a seed yield of 157 g m^?2 (mean temperate cultivars) compared to 249 g m^?2 (tropical cultivars), which was due to having lower values of pods, seed number and TDW. In addition, the occurrence of shriveling and smaller seed size compared to plants grown in their region of origin was considerably evident in Japanese cultivars. To account for the difference of growth duration, a maturity-corrected index for yield and relevant variables was calculated to consider the amount of incident solar radiation. The yield index for all tested cultivars ranged from .49 to 1.48, and Japanese cultivars showed the lowest yield index (.67), followed by US cultivars (.87), whereas tropical cultivars had index means from 1.05 to 1.20. Although they were both of temperate origin, Japanese cultivars tended to show a lower index than US cultivars. The tendency was similar for TDW and node number. The poor performance of temperate cultivars even after correction suggests that there is a genetic variation of adaptation to a tropical environment independent of growth duration. Additionally, there was considerable performance variation within temperate cultivars.     

Ruminal epithelial insulin‐like growth factor‐binding proteins 2, 3, and 6 are associated with epithelial cell proliferation

The aim of this study was to identify factors that regulate ruminal epithelial insulin‐like growth factor‐binding protein (IGFBP) expression and determine its role in rumen epithelial cell proliferation. Primary bovine rumen epithelial cells (BREC) were incubated with short‐chain fatty acids (SCFAs) at pH 7.4 or 5.6, lactate, lipopolysaccharide (LPS), insulin‐like growth factor‐I (IGF‐I), ‐II (IGF‐II), or recombinant bovine IGFBP2 (rbIGFBP2). The mRNA expression levels of IGFBP in BREC were analyzed using quantitative real‐time polymerase chain reaction (qRT‐PCR). The proliferation rate of BREC was analyzed using a WST‐1 assay. IGFBP2 gene expression tended to be lower with SCFA treatment (p < .1), and IGFBP6 gene expression was significantly lower with SCFA treatment (p < .05). IGFBP3 and IGFBP6 gene expression tended to be higher with d ‐Lactate treatment (p < .1). IGFBP3 gene expression was significantly higher (p < .05) with LPS treatment. BREC treated with IGF‐I grew more rapidly than vehicle control‐treated cells (p < .01); however, recombinant bovine rbIGFBP2 inhibited IGF‐I‐induced proliferation. IGF‐II and/or rbIGFBP2 did not affect BREC proliferation. Taken together, SCFA treatment decreased IGFBP2 and IGFBP6 expression in rumen epithelial cells, and lower expression of these IGFBP might promote rumen epithelial cell proliferation by facilitating IGF‐I.