‘Touki’, plants, Angelica acutiloba Kitagawa, are usually cultivated in soil, under which its yield and root quality are unstable. Although fertilizer application exerts a substantial impact on yield, the optimal level has not been known for the cultivation in soil. Therefore, the present study was undertaken to examine the growth ofToukiplants with different concentrations of nutrient solution in aeroponic and drip irrigation systems. Four nutrient concentrations, i.e., 100%, 200%, 50%, and 25% of the standard nutrient solution (“Enshi”formula) were tested: . In the aeroponic system, where a mist of nutrient solution was sprayed around suspended roots of the plants, the plants were grown from March 15 to June 6, 2005. In the drip irrigation system the plants were grown from May 2 to July 25, 2006. In the aeroponic system, the values of the growth parameters of the Touki plants at 12 weeks after transplanting were higher in the order of 100%>50%>200%>25% of the standard solution. In the drip irrigation system the growth parameters were higher in the order of 100%>200%>50%>25% of the standard solution. The “Enshi” nutrient solution of 100% was optimal for the growth of the Touki plants in both systems. The plant growth, especially root growth, was more vigorous in the aeroponic system than in the drip irrigation system. In the drip irrigation system, however, the root/shoot ratio and root C/N ratio were higher, and the development of secondary roots was stimulated. As the secondary roots of Touki plants are mainly used as raw materials for medicine in Viet Nam, the drip irrigation system is recommendable as an advanced culture system.

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Floating or deepwater rice (Oryza sativa L.) responds to submergence by rapid internodal elongation. The involvement of acid-induced growth and the pH-dependent wall-loosening protein expansin in such Internodal elongation was examined. Living internodal sections excised from floating rice stem segments that had been submerged showed significant enhancement of their growth in an acidic buffer, with the response maximized at pH 5.5. Such acid-induced growth was observed only in the basal regions of submerged internodes but not in any internodal regions of air-grown stem segments. Although the ability of isolated cell walls to extend in acid solution was the highest in the basal region of internodes and declined with distance from the base in both submerged and air-grown stem segments, submergence expanded the Internodal zone in which cell walls can extend in response to acid solution. There were no differences between the spatial distributions of extractable expansin activity of cell walls in rapidly elongating submerged internodes and those of air-grown internodes of floating rice, whereas only the growing region of submerged internodes showed particularly high susceptibility to added expansin. Our results suggest that the acid-growth process might be involved in the enhanced growth of internodes in submerged floating rice and that the process might be regulated mainly by changes in the susceptibility of the cell wall to expansin.

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Peatlands are characterized by high groundwater levels, low pH, and low nutrient contents. The growth rate and size of sago palms (Metroxylon sagu Rottb.) grown on peatlands are low. Two field experiments were conducted on Tebing Tinggi Island, Riau Province, Indonesia. In Experiment 1, the importance of minor elements was investigated by excluding each from the composite fertilizer. In Experiment 2, four treatments were prepared by combining the presence/absence of dolomite and chemical fertilizers, consisting of the major and minor elements. Solid fertilizers were spot-applied. The effects of minor element and dolomite applications were evaluated based on the growth parameters and their concentrations in leaves of 5-year-old sago palms from the transplanting time, when sago palms were still at the rosette stage. Plant height and the number of leaves did not differ significantly among the treatments in both experiments. In Experiment 1, there were no significant differences in the amounts of minor elements in the leaves among the treatments. Although the application of dolomite plus chemical fertilizer exerted a small beneficial effect on the K content in leaves, no other differences were observed in the contents of major and minor elements among the treatments in Experiment 2. Our findings indicate that spot application of solid salts is an ineffective means of delivering fertilizer to sago palms growing in peat soils.

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We conducted a number of screenings investigating antagonists which inhibit the growth of three pathogens (Streptomyces ipomoeae, Ceratocystis fimbriata, Macrophomina phaseolina) of sweet potato, and which are able to establish themselves in the rhizoplane of sweet potato. In the first screening, among the 500 fungal isolates which were obtained from the epidermal tissue of the storage roots, 12 fungal isolates (Penicilliumspp.) which inhibit the growth ofS. ipomoeaein dual culture were selected. These isolates also inhibited the growth ofC. fimbriataandM. phaseolina. In the second screening, herbaceous cuttings of sweet potato were cultured in sterilized water for two weeks with each of 12 fungal mycelium colony blocks (6mm in diameter), followed by reisolation of the 12 isolates from the rhizoplanes of herbaceous cuttings. Five isolates were reisolated from 90% or more of the root tissues, and these were selected for further investigation. The third screening was performed using a pot test in order to examine the control efficiency of the five isolates against soil rot of sweet potato caused byS. ipomoeae. In the pot test, the fungal isolates were cultured on wheat bran, then they were incorporated into artificially infested soil, and then sweet potato herbaceous cuttings were planted in the pots. Disease severity was evaluated by determining the proportion of canker lesion area which was observed on the subterranean stems; the effectiveness of the control by one isolte designated as B1-35 was good, having a protective value of 60.1. Since we were able to reisolate B1-35 from 97.5% of these roots, it was selected for further investigation. Dipping herbaceous cuttings of the sweet potato into a spore suspension (ca.10⁹cfu/ml) for 10 minutes or longer was effective in stably establishing B1-35 in the rhizoplane. Field trials were run in naturally infested fields; for this, seedlings of sweet potato were dipped into a spore suspension (ca.10⁹cfu/ml) of B1-35 for 12 hours. Disease severity was evaluated by determining the amount of necrotic area on the storage roots after harvest; the effectiveness of B1-35 was remarkable, having a protective value of 67.6. Furthermore, one month after harvest the decay rate of the storage roots byM. phaseolinawas repressed compared with the control. An analysis of the ITS-5.8SrDNA nucleotide sequence of B1-35 identified this isolate as Penicillium geastrivorus (Petersonet al., unpublished species) . These findings suggested that P. geastrivorusB1-35 could be used as a practical biological agent for the control of some pathogens of sweet potato.

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The pollination efficiency of two species of honeybees and bumblebees (Bombus ignites) was compared for‘Irwin’mango fruits grown in plastic greenhouses. The ratio of perfect bisexual flowers of‘Irwin’mangoes exceeded 50% in the distal part of the panicles, but tended to decrease toward the proximal part. The number of staminate flowers tended to increase in the proximal part. On fine days, visiting frequency of Japanese honeybees (Apis cerana japonica) to flowers in a panicle was twice as high as that of European honeybees (A. mellifera), while no differences were noted on rainy days. The number of bumblebees that visited the flowers on rainy days was only about 15% of the number on fine days. On the other hand, the duration of foraging of European honeybees was the longest on a panicle, followed by that of Japanese honeybees and bumblebees. Japanese honeybees commonly moved from flower-to-flower, while European honeybees tended to stay on the same flower panicle. Although the foraging duratuon of European honeybees was shorter on rainy days, the effect of the weather conditions on the foraging duration in Japanese honeybees and bumblebees was not significant. No differences were detected in the number of bees leaving the hives on fine and rainy days. The seeded fruit ratio was high with all three pollinators: 71.7% for Japanese honeybees, 69.0% for European honeybees and 59.3% for bumblebees. Although a larger number of fruits weighed more than 200 g with European and Japanese honeybee pollinators, bumblebee pollinators produced many small fruits weighing less than 100 g. The results showed that both European and Japanese honeybees are effective pollinators for the production of large mango fruits.

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Effect of the planting density on the growth and main stem yield in kenaf (Hibiscus cannabinusL.) was investigated at the Agriculture and Forestry Center, University of Tsukuba, in 2003 and 2004. Kenaf (cv.: KB2) plants were grown at three plant densities: namely, high density (HD), 44.4 plants m^-2 (15cm×15 cm spacing) ; middle density (MD), 22.2 plants m^-2 (30cm×15cm) ; and low density (LD), 11.1 plants m^-2 (30cm×30cm) . The experiment was laid out in a latin square design with three replications. The field was fertilized with 12g m^-2, 6g m^-2and 3g m^-2of N, P₂O₅, K₂O for HD, MD and LD, respectively. Seeds were sown late in May. Ten to 15 plants were sampled twice (141 days after sowing (DAS) and 168 DAS in 2003, 152-154 DAS and 188-191 DAS in 2004) for the measurement of the fresh and dry weights.
As a result, the value of the plant height and number of nodes were higher in the HD plants than in the LD plants during the former cultivation period. However, during the latter period, plant height in the LD plants had caught up with that in the HD plants and increased compared with the height of the HD. The HD plants showed a higher bast yield per unit area, whereas the LD plants showed a higher bast yield per plant. Stem diameter was so large that mechanical harvesting was possible for the HD plants. In conclusion, a planting density of 44.4 plants m^-2was found to be adequate for high bast yield and mechanical shoot harvesting in kenaf cultivation.

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Seasonally waterlogged swamps are often developed on the plateaus of tropical Africa. Agricultural land uses in such swamps have been very limited and most of the swamps lay uncultivated or were used only for grazing of cattle. Seasonal swamps on the Mbozi Plateau in Tanzania have been cultivated by adopting indigenous cultivation systems, theihombeand the vilimbika. Theihombesystem is a grass fallow system with slash-and-burn cultivation of finger millet, in the upper margin of seasonal swamps to avoid flooding. The traditional vegetable gardens, vilimbika, cover gentle slopes near springs for irrigation in the dry season. Recently, agricultural land use has undergone drastic changes, namely rainfed maize fields and paddy fields have expanded rapidly. For the maize fields in swamps, deep drainage system is implemented, based on indigenous practices of vilimbika system. The paddy fields can be located in areas with deeper flooding by taking advantage of the flooding conditions, which are unsuitable for the cultivation of other crops. Both systems can be applied over wide areas in the seasonal swamps, and may contribute to the rapid expansion of agricultural land use on uncultivated land in seasonal swamps.

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