CHANGES IN FOLIAR AMMONIUM CONCENTRATIONS IN SUBSTRATE-GROWN STRAWBERRY

Strawberries (Fragaria × ananassa Duch. cv. Nyoho) grown in peat-based substrate often suffer interveinal chlorosis in their immature leaves 10–20 d after planting. Based on our previous results and observations from growing practice, we hypothesized that the cause of this phenomenon could be due to drastic changes in plant nitrogen (N) nutrition in strawberries just after planting into peat bags. To determine optimal sampling time, diurnal variations in foliar ammonium (NH₄)-N concentration were evaluated under greenhouse conditions. Results showed a broadly similar pattern of diurnal variation, with the rates increasing to a maximum at midday and decreasing steadily during the second-half of the light period. However, foliar NH₄-N concentration was higher under sunny than under cloudy or shaded light conditions. In the second part of this study, changes in foliar NH₄-N and in nitrate (NO₃)-N in petioles in relation to the occurrence of interveinal chlorosis were investigated. When the plants were supplied with 30 (control) or 50% ‘Ohtsuka A’ nutrient solution for two weeks after planting, foliar NH₄-N concentrations increased earlier than petiole NO₃-N concentrations, and reached their peak 8 and 10 days after planting in 50% (1.90 μmol g^?1 FW) and 30% (1.78 μmol g^?1 FW) treatment respectively. Interveinal chlorosis was observed in immature leaves in 50% treatment about 10 days after planting while there was no chlorotic symptom in control treatment. The absence of interveinal chlorosis in immature leaves in control plants, led to the conclusion that a high leaf NH₄-N concentration and related accumulation of NH₄-N play an important role in triggering interveinal chlorosis.     

Amaranthus genetic resources in Indonesia: morphological and protein content assessment in comparison with worldwide amaranths

The morphological variations (growth habit, leaf shape, leaf color, height, stem diameter, number of branches and internodes, leaf area, blade ratio, leaf thickness, number of leaves, and total leaf area) and protein content of 53 Indonesian amaranths (Amaranthus spp.), consisting of weedy-, vegetable-, and ornamental-types, were assessed. The extent of variation in the Indonesian Amaranthus accessions were compared with the worldwide collection (26 accessions from United States Department of Agriculture (USDA) and 5 ornamentals from Nepal) in the experimental field of the University of Tsukuba, Japan. The variation in average values of most morphological traits and protein content in the Indonesian accessions were similar to those of the worldwide germplasm, but the important parameters that influence vegetable yield (e.g., number of leaves and stem diameter) were superior in the Indonesian accessions. Protein content showed a positive correlation with the number of leaves, whereas a negative correlation was observed with leaf thickness. The Indonesian accession of A. viridis and A. dubius showed a great potential to be further selected as parental lines for high protein content and number of leaves. The relatively high protein content of the leaves of Celosia may also potentially serve as an alternative protein source in the tropics.     

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.     

The reduction mechanism of manganese in paddy soils

Hydroquinone method manganese (soluble in pH 7.0, 1 N-ammonium acetate solution containing 0.2 percent hydroquinone) and microbially active manganese (soluble in pH 7.0, 1 M-magnesium sulfate solution after flooding soils with or without Chinese milk vetch for 12 or 20 days respectively at 30°C) of 22 paddy soils were determined. The amounts of manganese reduced with sodium oxalate under acid conditions (oxalate method manganese (a) and (b), the former was determined under more rigorous conditions than the latter) were also determined and compared with hydroquinone method manganese and microbially active manganese.

Their levels of many soil samples representing soil groups were also determined to examine the dlfferences In amounts of active manganese among soil groups. The results obtained are as follows.

The relationship between microbially and chemically active manganese. 1) The amounts of microbially active manganese in soils were 48 to 68 mg Mn per 100 g oven-dried soil and these were increased by the addition of Chinese milk vetch. 2) The amounts of hydroquinone method manganese were less than microbially active manganese, and the amounts of oxalate method manganese (b) were larger than microbially active manganese. The amounts of oxalate method manganese (a) were the largest of all the types of manganese. 3) There were high correlations between the amounts of various types of active manganese described in 2). The levels of microbially and chemically active manganese. 1) The amounts of microbially active manganese lay between the amounts of chemically active manganese determined by the hydroqulnone method and by the oxalate method (b) In all soil samples representing soil groups. High correlations were found between these types of active manganese. 2) The hydroquinone method was considered to be unsuitable for quantitatively determining the amounts of chemicallY active manganese in soils of high organic matter content. 3) In both cases of microbially active manganese and chemically active manganese, tha widest range and the largest amount determined were both observed in strongly gley soila. The averages of theae types of active manganese were high in strongly gley soils, pea, and muck soils, and black soils. The differences among soil groups were smalle1 than the differences among soil samples, and little tendency was observed in the differences among soil groups.

From these findings described above it is suggested that the oxalate methoo (b) is more appropriate than the hydroqulnone method for determining chemically active manganese as an index of microbially active manganese.     

Response of differentiated and degenerated spikelets to top-dressing,shading and day/night temperature treatments in rice cultivars with large panicles

The presence of large panicles enables to reach a sufficient number of surviving spikelets per unit area for further increase of rice yield. However, the response of differentiated and degenerated spikelets to environmental factors in terms of number in cultivars with large panicles has not been elucidated. By applying top-dressing at different rates and frequencies, shading, and day/night temperature treatments in pot experiments, we observed the response of the main stem in two cultivars with large panicles: Yangdao 4 (Chinese indica) and Akenohoshi (Japanese japonica-indica hybrid). The results showed that top-dressing increased the number of differentiated spikelets per panicle and decreased the percentage of degenerated spikelets. Consequently, the number of surviving spikelets per panicle increased. Shading increased the percentage of degenerated spikelets, resulting in the decrease of the number of surviving spikelets per panicle. Higher day/night temperature treatments led to a higher percentage of degenerated spikelets. The treatments affected mainly the spikelets on the secondary branches, while the number of spikelets on the primary branches did not change appreciably, irrespective of the presence of differentiated, degenerated, and surviving spikelets. The influence on the number of surviving spikelets per panicle depended on the number of differentiated spikelets. Shading effect on the percentage of degenerated spikelets also depended on the number of differentiated spikelets per panicle. The decrease of the percentage of degenerated spikelets was associated with the increase of the shoot dry weight (SDW) at heading and the ratio of SDW-differentiated spikelets. The SDW and N absorption at heading affected more significantly the number of surviving spikelets compared to the ratio of surviving spikelets-SDW and surviving spikelets-N, respectively. The above results were similar in Akenohoshi and Yangdao 4. In Akenohoshi, the percentage of degenerated spikelets responded much more conspicuously to the change of SDW or the ratio of SDW -differentiated spikelets than that in Yangdao 4. So did the number of surviving spikelets to SDW and N absorption at heading. Akenohoshi showed a higher ratio of surviving spikelets-N than Yangdao 4. These differences may account for the fact that Akenohoshi showed a larger number of surviving spikelets per panicle than Yangdao 4, even at the same levels of SDW and N absorption.     

An index for evaluating the flood-prevention function of paddies

Urbanization is expanding in and around small to medium-sized cities as well as in large cities, and the expansion includes low-lying areas where the flood risk is high. Flood risk in small watersheds has been evaluated using precise mathematical models. However, these models cannot be applied to larger basins due to the complexity of data collection and analysis. As a result, quantitative evaluations of flood risk at macro scales and the flood-prevention function of paddies around urban areas have not been made. This paper proposes a method and an index that can be used to evaluate the flood-prevention function of paddies on a regional scale. In addition, the use of this system for basin-wide management is illustrated by an example for the Kinu and Kokai rivers, which are tributaries of the Tone River of Japan. The applicability of the approach is evaluated using data from a major flood that occurred in the study area.     

Water penetration into rice grains during soaking observed by gradient echo magnetic resonance imaging

The water penetration into a rice grain during soaking was monitored by three-dimensional gradient echo magnetic resonance imaging, which has the advantage of a short measurement time and a sufficient sensitivity for low-moisture samples. The water penetration route was compared between the milled and brown rice grains of two japonica cultivars. In normal milled rice grains of Koshihikari, water first penetrated the ventral side surface and the embryo attachment site of the endosperm, then migrated along the central line and transverse cracks, and finally diffused to all parts of the endosperm. In milled rice grains of Yamadanishiki with a white core, water quickly infiltrated into the cracks or chalky parts on the dorsiventral line and then diffused to the lateral side. In brown rice grains of both cultivars water penetrated extremely slowly and did not infiltrate directly into transverse cracks or the white core due to inhibition by the pericarp and seed coat. The central part of every grain allowed more water to penetrate. The route, pattern and speed of water penetration were determined by the morphological structure, crack formation and hardness distribution associated with the packing of the starch granules in the grain.     

Identification of Ligands for Chicken Transient Receptor Potential Ankyrin 1 Channel and Chemosensory Perception of Herbal Compounds in Chickens

The pungency induced by spices and herbs plays an important role in food choice and appetite, and it is suggested that adding spices and herbs to feed as natural alternatives to antibiotics has beneficial effects in poultry farming. However, our knowledge of the chemosensory perception of herbal compounds in chickens is limited. Transient receptor potential ankyrin 1 (TRPA1) is involved in the sensory perception of various herbal compounds. Here, we performed calcium imaging and electrophysiological analyses using cells transiently expressing chicken TRPA1 (cTRPA1) and identified two novel cTRPA1 ligands—eugenol and thymol. In a behavioral assay, chickens responded to cTRPA1 ligands, including eugenol, thymol, cinnamaldehyde, carvacrol, and allyl isothiocyanate. These results provide evidence that chickens have a functional TRPA1 channel and chemosensory perception of various herbal compounds.