Melon (Cucumis melo L.) fruits was respectively treated with solutions of 500 mg L^-1 of 4-CPA (4-chlorophenoxyaceticacid) and 20 mg L^-1 of CPPU (2-chloro-4-pyridyl-N-phenylurea) and then cell size and sugar accumulation in the fruit were investigated. The mean number of cells larger than 200 μm for each rectangular parallelepiped (7-mm long sample serially collected beginning at one end of the 10-mm wide strip removed from the 10-mm thick disk at the maximum transverse diameter of the fruit to the opposite end. Designated as a sample) of the 4-CPA and the CPPU-treated fruits on the 40th day after anthesis (DAA) was 1.4 times higher than that of the control. The mean number of cells smaller than 200 μm per sample of the CPPU-treated fruits on the 55th DAA was 6.5 times higher than that of the control. Mean sucrose content per sample of the 4-CPA and the CPPU on the 55th DAA was 1.7 times as much as that of the control, and the mean glucose and fructose content of the CPPU-treated fruit on the 55th DAA was the highest, being 1.5 times higher than that of the control. Thus, it might be considered that the earlier increase in the number of larger cells in the 4-CPA- and the CPPU-treated melon fruits is related to a larger content of sucrose, and the increase in the number of small cells during the latter period of the CPPU-treated fruits participates in the largest content of glucose and fructose.

抄録全体を表示

A low agricultural productivity in northeastern Thailand primarily results from saline soils predominately distributed throughout the region. We proposed a remediation technique for the saline soil by using a solar-powered pump and subsurface drainage system (SPSD system) . This study was conducted in Khon Kaen Province, northeastern Thailand. The SPSD system could lower the groundwater levels and subsequently reduce the capillary rise of saline groundwater toward the soil surface. The SPSD system first collects excess groundwater through the drainage pipes connected to a water tank under the ground. Groundwater collected in the tank is automatically discharged out by the solar-powered pump. The electrical conductivity of groundwater (EC_w) measured in the area where the SPSD system was installed suggested that lowering of the groundwater levels using the SPSD system could enhance salt leaching from the soil profile by rainfall. The electrical conductivity of soils at the sampling point where the SPSD system was installed was lower than those obtained from the same soil profile at the control sites. Consequently, this study suggests that lowering groundwater levels using the SPSD system may be an effective means for reducing salinity degree of soil and groundwater in northeastern Thailand.

抄録全体を表示

The effect of increasing atmospheric CO₂ concentration on fine root distribution of potatoes and associated soil biology activity under subarctic conditions has not been studied. Potatoes (Solanum tuberosum L.) were grown in open top field chambers at three CO₂ concentrations [ambient (A) ; A+175μmol mol^-1 CO₂ (A+175) ; A+350 μmol mol^-1 CO₂ (A+350) ] and in ambient CO₂ plots with no chambers (ANC) on a Tanana silt loam (non-acid loamy, mixed Pergelic Cryaquept) at Fairbanks, AK in 1994. Soil cores to a depth of 60 cm were taken at 0, 19, and 38 cm perpendicular to row center; root variables were ascertained at four 15 cm depth increments. Soil cores to a depth of 15 cm were also collected to assess soil biology (dehydrogenase activity, nematodes, and soil microarthropods) . Elevated CO₂ did not enhance root densities (i.e., both length and mass) at any depth or row position; there was no significant CO₂×depth, CO₂×position, or CO₂×depth×position interactions for measured root variables. Significant depth×position interactions were noted. In general, a higher proportion of the potato root system grew closer to the row center (root length and mass bases) most notably at the uppermost soil depths. Elevated CO₂ had no impact on the soil biology parameters evaluated in this study. Our field results suggest that increased atmospheric CO₂ concentration did not alter belowground responses in potato under subarctic conditions of Alaska.

抄録全体を表示

The objective of this work was to study the induction of the root ferric-chelate reductase (FCR) activities, and to reveal differences in the tolerance to Fe-deficiency chlorosis among four Asian pear rootstock species (Pyrus spp.) grown in nutrient solution with or without Fe. Our result showed that the induction of root FCR activity was dependent on the root area. The highest FCR activity was found in lateral root tips. The FCR activity of root tips under Fe-deficiency stress significantly increased in four pear rootstocks, while the FCR activity of intact roots under Fe-deficiency stress slightly increased except Pyrus xerophila Yü, but no significant difference in both treatments with or without Fe. Under Fe-deficiency stress, Pyrus xerophila showed greater contents of leaf chlorophyll and“active”iron, and higher FCR activity in roots tips than the other three pear rootstocks, Pyrus calleryana Decne, Pyrus betulaefolia Bunge and Pyrus pyrifolia Nakai. Our results suggested that Pyrus xerophila may be more tolerant to Fe-deficiency chlorosis than other three rootstocks. There was a strong induction of the FCR activity in root tips of all pear rootstocks. The measurement of FCR activity in root tips may be a suitable indicator to assess tolerance of Fe-deficiency chlorosis for selecting efficient Fe-uptake pear rootstocks.

抄録全体を表示

The effects of controlling minimum nocturnal ambient air temperature, day length and culture medium temperature on growth and yield were studied for the purpose of developing a year-round cultivation system for wasabi (Eutrema japonica (Miq.) Koidz.) . When the minimum night temperature was 5°C in winter, the growth of wasabi leaf was slow but recovered when the temperature rose to 8°C. Extension of day length by supplemental lighting was found to enhance growth recovery. Wasabi was planted at different times of the year to compare the effects of seasonal variation on stem growth. The mean daily growth medium temperature was maintained at 13.5-28.1°C throughout the year. These results revealed little difference in growth and stem pungency due to the season of planting, and stems grew to about 60 g within two years of cultivation. Year-round, stable nutrient solution cultivation of wasabi under environmental control may be an economically feasible alternative to conventional, labor-intensive cultivation systems.

抄録全体を表示

This study was conducted to examine the effect of temperature on heterosis in photosynthetic characteristics in F₁ hybrid rice (Oryza Sativa L.) from a thermo-sensitive genie male sterile line. At the active tillering stage, photosynthetic parameters were measured at 5 temperature levels (20, 25, 30 35 and 40°C), and chlorophyll fluorescence quenching was measured at 25°C in the F₁ hybrid and its parents. Within a temperature range of 20-35°C, CO₂ exchange rate and other photosynthetic characters viz., stomatal conductance and transpiration rate were lower in the F₁ hybrid than the male parent. On the other hand, at 40°C, these characters were higher in the F₁ hybrid than in parents. Non-photochemical quenching in the F₁ hybrid was higher than that in parent cultivars, whereas no significant differences in effective quantum yield of photosystem II, electron transport rate or photochemical quenching were observed between the F₁ hybrid and parent cultivars. It is considered that the positive heterosis for CO₂ exchange rate at higher temperature was due to the higher stomatal conductance and the higher non-photochemical quenching.

抄録全体を表示

Effects of planting density and raising seedling method on the flowering, yield and quality of snapdragon (Antirrhinum majus L.) were investigated. Plants were sown in July and pinched in September. In experiment 1, ‘Maryland Pink’ and ‘Light Pink Butterfly II’ were pinched at the temporary planting stage followed by planting at a density of 4, 6 or 8 plants per row. The yield of cut flowers per plant decreased with an increase in planting density. However, the yield of cut flowers per square meter was significantly less in 4 plants per row than in 6 and 8 plants per row. The number of days from pinching to flowering and cut flower quality were not affected by the planting density. In experiment 2, ‘Maryland Pink’ was non-temporary planted with the same density as in experiment 1 or planted after temporary planting as a conventional method with 6 plants per row. Effect of planting density in non-temporary planting was similar to that of‘Maryland Pink’ in experiment 1. The flowering of the primary shoots on the second node was earlier in non-temporary planting than in the conventional method, and the yield of cut flowers was greater in the former than in the latter. The results show that the productivity was higher in raising seedlings without temporary planting than in the conventional method.

抄録全体を表示

The structure of water induced by a high-temperature sintered kaolinite ceramics treatment was studied in view of thermally stimulated depolarized current (J) and temperature profiles (TSDC analysis) on the iced treated water and ¹H-Nuclear Magnetic Resonance (NMR) spectrometry on the treated water as well as some physical properties of the sintered ceramics. In addition, some biological effects of the treated water were examined to give indirect evidences for the proposed water structure. The treated water were positively charged based on essentially the formation of electric double layer interface between the ceramics surface and water flow, without any absorption-desorption phenomena to substances contained in water to be treated by the ceramics. The positive charge was indirectly affirmed by TSDC and ¹H-NMR analyses on ionexchanged water and for the drinking water. The water structure derived by the existence of chlorine substances was apparently disappeared from ¹H-NMR spectrum, probably by the apparent neutralization or accumulation of chlorine substances through interaction with positive charge. This phenomenon seemed to be closely related with the fact that absorption of chlorine ion through a vegetable root was greatly depressed when the treated water by the ceramics was used. The treated water was also proved to restrict the growth of E. coli in poor nutritional culture media and the production of bacterial cellulose by CFJ-002 (New bacterium cellulose-producing microorganism, an enterobacter) stock, and to suppress the oxidation action of hydrogen peroxide.

抄録全体を表示

This study was conducted to determine the effects of electrolyzed solution (alkaline solution and mixed solution, mixed with the same volume of alkaline and acid solution) and nonelectrolyzed solution (KCl solution), with different strengths, on the growth of radish (Raphanus sativus L.) sprouts. The electrolyzed solution was generated by dissolving KCl, as an electrolyte. The 1/1 (247 mg L^-1 of K⁺ concentration) and 112 (124 mg L^-1 of K⁺ concentration) strength alkaline solutions promoted the plant growth. Among the 1/1 strength solutions, the plant growth was most superior in alkaline solution, followed by mixed solution (176 mg L^-1 of K⁺ concentration), and less superior in KCl solution (175 mg L^-1 of K⁺ concentration) . One of the reasons of the accelerated plant growth in 1/1 strength alkaline solution may be due to higher K⁺ concentration in the solution, because K⁺ acts as a fertilizer. However, in spite of the K⁺ concentration in 1/2 strength alkaline solution was lower than that in 1/1 strength mixed and KCl solutions, the plant growth was more promoted in 1/2 strength alkaline solution. Therefore, the superior plant growth in alkaline solutions may concern not only K⁺ concentration but another factors, for example, lower oxidation-reduction potential (ORP) in the solution and/or easiness of mineral absoption by electrolysis.

抄録全体を表示

This paper describes the evaluation of the properties of a portable ion analyzer (Culturyzer-mini) for measuring the concentrations of ions used in hydroponic nutrient solutions. This analyzer uniquely includes a disposable sensor card that contains electrodes, a calibration solution, a heater and a drain reservoir. The analyzer is compact and requires minimal maintenance and user interaction, and is able to give results with only 200 μL of solution within 3 min. Together with pH and EC, the following ions can be measured using two kinds of sensor cards: K⁺, Ca²⁺, Mg²⁺, H₂PO₄^-, NO₃^-, NH₄⁺. The sensor signal revealed a linear output over the wide range of specific standard solutions. Correlation coefficients between the Culturyzer-mini readouts and conventional methods, such as ion chromatography, a pH meter and a conductivity meter, were over r=0.9 and the coefficient of the variables for day by day use were within 10% CV for all items. This analyzer is able to reduce environmental pollution, since it allows more effective nutrient management and thereby reduces the amount of fertilizer waste in hydroponic systems. The utility and the problems of the analyzer are also described.

抄録全体を表示