Sweetpotato (Ipomoea batatas (L.) Lam.) research requires a cultural technique that ensures tuberous root formation for elucidation of the morphogenesis mechanism. Singleroot cuttings were grown in a hydroponic system, where the basal part of the root was exposed to the air and the distal part was immersed in nutrient solution. In all of the plants grown in the system, the nodal root swelled in the aerial space, and the thickened part revealed the anatomical characteristics of the tuberous root. The formation of the storage organ occurred earlier in initially thicker roots. After the storage organ initiation, number of leaves in the cuttings affected the thickening growth of the tuberous root.

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In order to provide further information on the relationship between the occurrence of“sakibosori” fruit disorder and the fruit growth activity, a descriptive model of the growth of cucumber fruit under increasing levels of salinity at low oxygen supply levels in the nutrient solution was developed. Assumptions of the model were as follows : (i) the upper limit of the growth rate in volume of a fruit (GR_max) is determined by the following equation : GR_max=A/ (1+exp (B (x-C+De) ) ) +E, where A, B, C, D and E are constants, x is NaCl concentration (mM) and e is a standard Gaussian noise with mean 0 and variance 1; (ii) a fruit grows exponentially until its growth rate reaches GR_max, thereafter linearly. The model reproduced fairly well the all-or-none probabilistic patterns of the response of the relative growth rate of fruits to salinity at low oxygen supply levels in the nutrient solution in spring culture, which had been measured in earlier experiments. It was also suggested that there can be a seasonal difference in the parameters of above equation.

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To feedback plant water requirement into control of solution supply in hydroponics, we developed a method to measure drainage flow rate continuously. Drainage accumulates in an apparatus which we have developed, and its weight is measured continuously by a balance. Continuous measurement of drainage makes real-time monitoring of water uptake by plants practicable. We examined the usefulness of this method for controlling the supply of nutrient solution in an aeroponics of cucumbers (Cucumis sativusL.) . We compared two methods of controlling the nutrient solution supply. As a new method, to determine the amount of solution supply on the following day, we fit an equation relating water uptake to solar radiation. As a conventional method, solution was supplied whenever the integrated solar radiation reached 0.0926 MJ m^-2 and fed back daily leaching fraction of a previous day into the control. In the first half of the experimental period, the water uptake in the new method was higher than the conventional method. In the second half, water uptake was similar for the two methods. Fruits yield of the new method was significantly higher than the conventional method.

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Effect of photoperiod on flowering response and growth of 18 ornamental sunflower cultivars was evaluated. Plants were grown in a glasshouse under 16 h long day (LD) or 11.5 h short day (SD) conditions. In 12 of the cultivars tested (66.7%), visible flower bud stage was significantly earlier under the SD than under the LD. All of the cultivars flowered under both the SD and the LD conditions. However, 16 cultivars (88.9%) had a quantitative SD response, that is, their flowering was significantly delayed under LD. Delay of flowering under LD was variable among the cultivars, and was 14 days or greater in 11 of them. Photoperiod had no effect on flowering of ‘Jamboree’. This cultivar behaved clearly as a day-neutral (DN) plant. The cultivar ‘Sailor Moon’ showed a LD response; its flowering was earlier under LD. In 14 of the cultivars showing a SD response, photoperiod also influenced plant height, resulting in taller plants under LD. In the most of cultivars there was no effect of photoperiod on flower and stem diameters.

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In existing FACE (Free Air CO₂ Enrichment) systems, efforts have been made to maintain the CO₂ concentration within a FACE ring at the setpoint value. Therefore, effects of only one elevated CO₂ concentration on plants and/or ecosystems can be examined with one ring. The basic idea of the present study was, instead of controlling the CO₂ concentrations within a ring at a constant value, to create and maintain a constant CO₂ concentration gradient within a ring. In this way, examinations of the effects of different CO₂ concentrations on plants and/or ecosystems would be realized using one ring. An artificial neural network was applied to control the CO₂ gradient within a ring of a stretched hexagon with ten CO₂ emitting tubes. The results of the experiments showed that when the wind speed was more than the detectable range by the anemometer (about 30 cm s^-1), a concentration gradient was in most cases observed, though not completely the same as the target gradient. When the wind speed was less than the detectable value, the CO₂ concentrations within a ring rose far above the target values and the gradient was not created.

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The interactions between vernalization and photoperiodic effects on inflorescence formation in radish varieties were investigated by applying a new index “flower formation index” to explain these effects quantitatively. According to “flower formation index, ” as the varieties that responded to the single treatment of either long day or low temperature by which the inflorescence formation dramatically accelerated, whereas either treatment hardly induced the inflorescence formation. Moreover, the condition of long day or short day on the varieties that showed insufficient photoperiodic induction comparatively has a dramatic effect on the inflorescence formation when it was at the condition of insufficient low temperature induction. Thus, the inflorescence formation of radish plants is dramatically influenced by photoperiod as well as by temperature, and the responses to these two factors significantly differ among the varieties. So it was supposed that interactions between vernalization and photoperiodic effects on inflorescence formation in radish varieties should be considered more that we considered until now.

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An efficient micropropagation system using the root culture were established in Oenanthe javanica DC. In the shoot tip culture, the tip portion of terminal bud or lateral bud was excised and cultured on the half strength Murashige and Skoog medium supplemented with 0.1 mg/L α-naphthalene acetic acid (NAA) or combination of 0.2 mg/L NAA and 0.2 mg/L 6-benzyladenine (BA) under continuous light of 45 μmol m^-2s^-1 at 25°C. In root segment culture, root explants which were whole roots excised approximately 1.5 cm length from aseptically generated plantlets were used and cultured on MS medium supplemented with 0.05, 0.1 or 1 mg/L 2, 4-dichlorophenoxy acetic acid (2, 4-D) and 0, 0.01 or 0.1 mg/L BA at 25°C in the dark. Embryogenic calli were induced on medium supplemented with 0.1 mg/L 2, 4-D and 0, 0.01 or 0.1 mg/L BA. Plant regeneration was successful on the MS hormone-free medium. Many embryos were developed into normal plants by subculture on the same medium. In vitro propagation with root and petiole sections of aseptically generated plants in vitro is more efficient than conventional shoot division ex vitro. The results indicate that the micropropagation procedure can be applied to an efficient propagation of Oenanthe javanica DC.

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The stomatal response to evaporative demand depending on air humidity and wind was analyzed in an intact cucumber leaf (Cucumis sativus L.) exposed to different conditions of air humidity and wind velocity in a leaf cuvette. The evaporative demand on the transpiring leaf was evaluated on the basis of the environmental factors within the leaf cuvette and was set at different values by changing the saturation vapor deficit and wind velocity within the leaf cuvette. Using a model leaf of wetted filter paper, a constant positive linear relationship was found between the evaporation rate and the evaporative demand even under different conditions of air humidity and wind velocity. On the other hand, the relationship between gas exchange parameters in the cucumber leaf (i.e., stomatal conductance, transpiration rate and photosynthetic rate) and the evaporative demand was discontinuously shifted due to the change in wind velocity even under the same humidity condition. These differences in the stomatal behaviors in relation to the evaporative demand, given by the respective changes in air humidity and wind velocity, were not attributed to the feedback stomatal response to the intercellular CO₂ concentration in the leaf. The mechanism of stomatal response to the evaporative demand, given by the respective changes in air humidity and wind velocity, was explained on the basis of the antagonism relationship between the guard and epidermal cell turgors that are directly affected by the leaf surface humidity and impact of the evaporative demand through water balance within the stomatal complex.

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Nutrient solution supplied to cucumber (Cucumis sativus L.) cuttings during low air temperature storage was warmed for 1 day to reduce water stress of cuttings during storage and advance their rooting after storage. Cuttings were stored for 7 days in air temperature of 12-14°C with photosynthetic photon flux density of 12 μmol m^-2 s^-1. Nutrient solution was supplied to the cuttings through the hypocotyl cut-ends during storage. The nutrient solution temperature was maintained at 28°C for 1 day after starting of storage or before end of storage. The nutrient solution temperature was maintained at 14°C on other days. During storage, fresh weight and relative chlorophyll content of the cuttings treated in nutrient solution of 28°C for 1 day after the starting of storage was maintained higher than those that were untreated. Three days after planting the cuttings following storage, root fresh weight of the cuttings treated in nutrient solution of 28°C for 1 day after the starting storage or before the ending storage was 1.7-1.8 times as large as those that were untreated. Treatment using the warming nutrient solution increased water absorption rate and transpiration rate of cuttings ; moreover, it reduced wilting of cuttings during storage. These results indicate that application of nutrient solution of about 28°C for 1 day after the starting storage reduced the water stress of the cuttings, maintained high chlorophyll content, and advanced rooting after the end of storage in comparison with nutrient solution of about 14°C during storage. As a result of applying the treatment at various temperatures, the rooting after storage was most promoted at 29-36°C.

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The objective of this study was to develop a practical diagnosis method of indoor trees based on laser induced chlorophyll fluorescence. We have suggested that two parameters, MM-gradient and MM-distance, could be used to analyze induction kinetics curve. Induction kinetics data of trees with low-irradiance stress, water stress, long-darkness-stress and short-darkness-stress were used for analyses by the two parameters, and a criterion based on the two parameters for judging whether the tree was stressed or not, was derived. Though the judgment using the criterion we found was not perfectly correct, it reflected the stress imposed on trees with a high probability and can be used in practical situations.

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We examined the relationship between the timing of heating the greenhouse in autumn and winter period and flowering of Disa orchid as part of efforts to develop and establish a stable method of growing with the suitable cultivars at the Yatsugatake Farm of the Yamanashi Agricultural Research Center (955 m above sea level, Takane, Hokuto) . In the 2001 experiment, flowering were promoted by rising the night temperatures from February 8. Heating treatment hastened flowering by about 20 days in D. Kewensis and about 40 days in D. Helmut Meyer. Flower stalks of the two cultivars were longer in heat-treated plants than in control plants. The number of flowers per flower stalk was not affected by the heating treatment except for D. Helmut Meyer which had fewer flowers in treated plants than in control. In the 2003 experiment, heating the greenhouse at night hastened the flowering in D. Cardior × D. uniflora and D. Helmut Meyer, but not affected in D. uniflora and D. Helmut Meyer. Only in D. uniflora, the length of flower stalk was shortened by earlier heating. The other three cultivars, (D. Cardior × D. uniflora, D. Margaret Ann Rundle and D. Helmut Meyer), were not affected by heating.

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