Simulation of direct and diffuse solar radiation transmission into a lean-to greenhouse with photovoltaic cells on the roof and with infinite longitudinal length was conducted using mathematical models by Kozai. The effects of area percent (0-100%) of photovoltaic cells on the roof, greenhouse orientation (E-W, E-W ±15°and E-W±30°), north latitude (25, 30, 35, 40 and 45°) and season (winter solstice, spring/autumnal equinox and summer solstice) on the diurnal time courses of averaged transmissivity for direct solar radiation on the floor surface, and the cross-sectional distributions of transmissivity for daily integrated global (direct+diffuse) solar radiation on the floor surface were analyzed. When the area percent of photovoltaic cells on the roof was lower than about 60-80 in the winter, 40-60 in the spring/autumn, or 30-50 in the summer at the north latitude of 25-45°, the reduction and unevenness of averaged transmissivity for daily integrated solar radiation on the floor surface due to the shade by the photovoltaic cells were not significant for a greenhouse with orientations of E-W, E-W±15° and E-W±30°. Thus, notable amounts of electricity can be generated using photovoltaic cells without significant reduction in solar radiation transmission, if the area percent of photovoltaic cells and greenhouse orientation are chosen properly at a given latitude (geographical location) and time of the year.

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The effects of (+) -S-abscisic acid (ABA) on the water status of stored tomato (Lycopersicon esculentum Mill.) plugs were investigated. Plugs were sprayed at the 4-leaf stage with ABA at 0, 20, 100, or 500 mg L^-1 and stored in the dark at room temperature for 10 d. The water status of the plugs and soil was measured with isopiestic psychrometers. No growth occurred during storage. Untreated plugs wilted : the water potential and turgor of their leaves decreased significantly. However, the water potential and turgor of leaves treated with ABA were maintained. These results suggest that ABA treatment reduces wilting by controlling transpiration and osmotic adjustment.

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The effects of deforestation on carbon balance in a natural tropical peat swamp forest were evaluated by micrometeorological monitoring. The monitoring sites were the primary forest at To-Daeng and the secondary forest at Bacho in Narathiwat Province, Thailand. The concentration gradient method (CG) and the relaxed eddy accumulation method (REA) were used to estimate the CO₂ flux above the canopies. We estimated the annual amount of carbon absorption for both sites, using the relationship between CO₂ flux and solar radiation for each site. An annual net carbon absorption of 5.32t C ha^-1 year^-1, was estimated for the primary forest. The accumulation of the released organic matter from the forest into logged-water caused the net carbon absorption in the peat swamp forest. In the secondary forest, annual net carbon absorption was estimated at 5.22 t C ha^-1 year^-1, which is almost the same range of absorption as the primary forest, because of plant growth in the secondary forest. A greater quantity of net carbon absorption, 9.69t C ha^-1 year^-1, was expected, assuming that the ground surface remained water-logged throughout the year. On the other hand, assuming it remained dry throughout the year, a net carbon emission of -0.40 t C ha^-1 year^-1, was expected.

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In order to evaluate the effect of matric component on water potential in gel medium for plant tissue culture, matric potential in agar gel and gellan gum gel was studied. Overburden potential was also studied to estimate the effect of overburden pressure to the gels. The suction plate method and the sand column method were used to measure the relationship between matric potential and gel concentration. Mechanical pressure was applied over gel and gel concentration was measured after water in gel and free surface water was in hydrostatical equilibrium. The matric potential for both gels decreased with their concentrations. The potential values were around -0.1 kPa or larger (=less negative) at gel concentrations normally used for plant tissue culture ; the values were less than 0.01% of the osmotic potential in MS medium which suggests that they are negligible as a component of water potential in gel medium. The mechanical pressures over gels agreed with the absolute values of matric potentials for the same gel concentrations. This suggests that the solid structure of the gel matrix had no resistance to deformation by the mechanical pressure and all of the mechanical pressure was transferred to the water in the gel to produce overburden potential. The syneresis from gel was concluded to be drainage of excess water during the process of hydrostatical equilibrium among gravitational potential, matric potential, and overburden potential. The amount of syneresis was shown to increase with lower gel concentration (=less negative matric potential) and with larger mechanical pressure. The change of syneresis with gel concentration and/or mechanical pressure by plant growth may influence the water condition of plant tissue in gel medium.

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Chervil (Anthriscus cerefolium L.), a kind of fresh culinary herb, harvested and packed in transparent polystyrene packages in a commercial operation was stored at 3°C for 27 d under different light conditions (dark, D; low light irradiation (LLI: a photosynthetic photon flux density of 1 μmol m^-2 s^-1) using red light-emitting diodes, R; LLI using a white fluorescent lamp, W) with application of agar-gel containing (C) or not containing (N) mineral nutrients to the stem cut-end. The color difference (ΔE*ab) value, measured through the upper cover of the package, of the leaves of chervil in RC and WC were significantly lower than the other treatments on the last day of storage (day 27) . The ΔE*ab values in RC and WC were kept at less than 3 (an inappreciable change-level by the naked eye) until day 21 and 24 respectively, while those in DN, DC, RN and WN were day 9, day 8, day 16 and day 16, respectively. A five-rank subjective visual quality score of chervil on day 27 in RC was significantly higher than WC, and those in RC and WC was significantly higher than RN and WN respectively. These results indicate that red light-emitting diodes were more effective than the white fluorescent lamp as a source for LLI, and the presence of mineral nutrients in the gel was essential for the best performance of LLI for preservation of the visual quality of postharvest chervil during low temperature storage.

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To study the combined effects of controlled water and nitrogen supplies on growth and yield of spring wheat (Triticum aestivum L.), plants were grown in a controlled environment chamber during the entire growth period. When the 3rd leaf was visible, three levels each of water and nitrogen supply, for a total of nine treatments, were applied using the system to accurately control soil water and nitrogen levels. There was a significant interaction of water and nitrogen levels on growth and yield of wheat. Under low water conditions few tillers were produced and the biomass production and grain yield were suppressed, whereas nitrogen supply level had little impact on the plants. With increasing water supply, on the other hand, the production of tillers, biomass and yield increased significantly. Furthermore, the nitrogen supply level had significant effects on growth and yield as the water stress decreased. Water and nitrogen shortages caused increases in phyllochron values. However, heading of the main stem was almost unchanged because of the compensation by a decreased number of leaves on main stem. The impact of water and nitrogen stresses on growth and yield was reflected primarily by the strong response of tillering at the individual plant level.

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We investigated water relations of fruit cracking in single-truss tomato (Lycopersicon esculentum Mill.) plants grown hydroponically in a greenhouse. At 24 d after anthesis, the water potential of the culture solution was changed from -0.06 MPa (control plants) to -0.36 MPa (stressed plants) . The water status of the culture solution and plant tissues was measured with an isopiestic thermocouple psychrometer. Fruit cracking decreased from>80% of fruit in the control to <30% in the stressed plants. The water potential gradient between fruit flesh and water source was greater in the control plants than in the stressed plants. Between predawn and morning, turgor increased in the fruit flesh in the control plants but not in the stressed ones. The hardness of the fruit skin was not different between stressed and control plants. These results indicate that the water potential gradient and increased turgor in the tissues might trigger fruit cracking in single-truss tomato plants.

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We evaluated the nutrient solutions to establish high-yielding hydroponics of paddy rice. Takatsuji-type and Otsuka-type nutrient solutions which contained NH₄-N, were more effective for vigorous growth with satisfactory plant length and tillers in early growth stages. In the case of Hyponica-Si- and Hyponica-type nutrient solutions, early growth was delayed slightly but it restored in the latter growth stages. From July when the NH₄-N concentration in the nutrient solution rose, plants grown in Takatsuji-type, Otsuka-type and Kimura-A-type nutrient solutions exhibited yellow-brownish leaf streak symptom with long leaf blades and wide spreading of tillers. The onset of the symptom was related to the low CaO concentration in these nutrient solutions.

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