塚越 覚

Grafted cucumber plants were grown in a new hydroponic system (“Kappa Land”, Mitsubishi Chemical Aqua Solutions, Co., Ltd., Tokyo, Japan). Two different nutrient management methods were applied to the plants as treatments: Electrical Conductivity-based Management (ECM) and Quantitative Nutrient Management (QNM). During the growth period, we examined plant growth characteristics and productivity, fruit growth characteristics and quality, and nutrient use characteristics. The results revealed that the QNM technique significantly reduced the nutrient supply rate per plant for Ca2+, SO42−, and N by 28.5%, 25.5%, and 23.3%, respectively. Similarly, the absorption rates per plant of SO42−, K+, and PO43− were reduced by 17.8%, 11.9%, and 10.9%, respectively. However, N, Ca2+, and Mg2+ absorption rates slightly increased in the QNM treatment. The nutrient wastes generated per kilogram of produced fruits were also reduced by 66.4%, 60.7%, and 30.2% for N, Ca2+, and SO42−, respectively. Although the QNM technique reduced the plant’s leaf area, it significantly increased its total length by 9.4%. The total and marketable yields were not significantly different between the ECM (9.0 and 8.0 kg plant−1) and QNM (9.1 and 8.2 kg plant−1) treatments. However, the QNM treatment produced the highest total dry matter of 617 g plant−1, surpassing the ECM treatment by 6.9%. On the other hand, differences in nutrient management methods did not significantly affect fruit quality, including total soluble solids, water content, skin color, size, and shape. These results suggest that with the QNM method, it is possible to produce quality cucumbers with high nutrient use efficiency while protecting the environment from nutrient wastes.

Cucumber (Cucumis sativus L., cv. “Nina Z”) plants grafted onto squash (Cucurbita maxima, cv. “Yu Yu Ikki”) were grown in a greenhouse using the newly developed nutrient film technique (NFT) hydroponic system “Kappa land” (Mitsubishi aqua solutions Co., Ltd., Tokyo, Japan ), from February to June 2022. The growth and development of cucumbers were examined under two different training methods: Lowering training (LT) and Pinching training (PT). Data collected were related to water and nutrient consumption, plant growth and development parameters, and the workload of the main activities. The results showed that plants grown under the LT recorded significantly higher total stem length (10.9 m) and number of nodes (133). In addition, from 21 April to 19 May, the leaf area index was significantly higher in the LT treatment. The highest total yield (15.4 kg m−2) and marketable yield per unit area (13.8 kg m−2) were recorded in the LT treatment. Regarding fruit growth, the fruits took 14 and 19 days to reach the standard harvest weight in the PT and LT treatments, respectively. In addition, the fruits were more straight in the PT treatment. The water use efficiency was not significantly different between the two treatments. However, the nutrient use efficiency was significantly higher in the PT treatment because plants produced more vegetative organs in the LT treatment instead of fruits. The work for removing old leaves and harvesting fruits was simplified in the LT treatment. The LT method can be effective for the automation of old leaf removal and fruit picking by the robot in the future.

Quantitative nutrient management has advantages, such as saving resources and improving nutrient utilization, compared with the conventional electrical conductivity management method. The growth and nutrient utilization of vegetables are affected by the integrated environmental conditions such as nutrient supply and light spectrum. This study investigated the effects of applied nutrient quantity (ANQ) (0.5, 1, 2, and 4 times (T) the absorption quantity of nutrients determined in the preliminary experiment, indicated by 0.5T, 1T, 2T, and 4T, respectively) in nutrient solution and red:blue ratio (R:B = 3:7, 7:3, and 9:1, indicated by RB3:7, RB7:3, and RB9:1, respectively) on the growth and nutrient utilization of basil plants in a plant factory with artificial lighting. Results demonstrated that the nutrient use efficiency (NUE) and the nutrient absorption efficiency (NAE) were significantly increased by the ANQ of 0.5T compared with the treatments of 1T, 2T, and 4T, irrespective of R:B ratios. Furthermore, under the ANQ of 0.5T, RB7:3 significantly increased the yield and the absorption of N and K of the basil plant compared with other R:B ratios. Therefore, the ANQ of 0.5T combined with RB7:3 was considered the optimal combination to improve the yield, NUE, and NAE of basil plants in the present study.

Plant factories with artificial lighting (PFALs), with well-insulated and airtight structures, enable the production of large quantities of high-quality plants year-round while achieving high resource use efficiency. However, despite the controlled environment in PFALs, variations in plant individuals have been found, which affect productivity in PFAL operations. Plant phenotyping plays a crucial role in understanding how the surrounding microenvironment affects variations in plant phenotypes. In the current study, a modular phenotyping system for seedling production was developed, focusing on practicality and scalability in commercial PFALs. Experiments on seedlings, which strongly affect productivity, were conducted to obtain cotyledon unfolding time and the time series projected area of cotyledons and true leaves of individual seedlings of romaine lettuce (Lactuca sativa L. var. longifolia), using RGB images. This was also undertaken to analyze how the surrounding microenvironment of photosynthetic photon flux densities and nutrients affect growth variations for plant cohort research. In agreement with the actual measurements, variations in seedling growth were identified even under similar microenvironments. Furthermore, the results demonstrated larger variations in seedlings with higher relative growth. Aiming for simplified interactions of phenotypes with the microenvironment, management, and genotype, seedling selection and breeding with plant production in PFALs may enable plant uniformity and higher productivity.

With the increase in dialysis patients worldwide, the demand for low-K vegetables is growing. Thus, a type of lettuce with a low-K content has been marketed in Japan. To learn more about low-K vegetables, information is needed on the physiological differences between these vegetables and those with typical levels of potassium (K). In this study, lettuces (Lactuca sativa L.) were cultivated using two low-K management methods in an environment-controlled system. One method was based on electrical conductivity (EC) management, and the K was replaced by sodium (Na) at the end of cultivation. The other method was based on quantitative nutrient management, and the nutrients required for low-K lettuce were quantitatively supplied, but no extra Na was added. Meanwhile, lettuce with normal K concentration was cultivated with EC management as the control. Plant growth indices, leaf photosynthesis traits, chlorophyll fluorescence characteristics, concentrations of secondary metabolites (SMs), and antioxidant activity were examined to investigate the physiological effects of low-K and high-Na concentrations during low-K lettuce cultivation. Both low-K treatments significantly restrained the growth of lettuce and increased the concentration of soluble sugar. However, photosynthesis and fluorescence characteristics remained unchanged. This indicates that the biomass reduction of low-K lettuce was due to the wasteful accumulation of carbohydrates rather than the decline in photosynthesis. Concentrations of SMs were increased in the low-K lettuce. In addition, higher concentrations of Na influenced the concentration of SMs, indicating that SMs were more sensitive to environmental stress.

Chronic kidney disease (CKD) has been a global health problem in recent years. CKD patients often restrict their potassium (K) intake to avoid the high risk of hyperkalemia. In this study, quantitative K management in hydroponics was adopted to produce low K cherry-type tomato (Solanum lycopersicom L.) fruit. The total quantity of K supply per plant during the cultivation was 7.2 g (1 K), 3.6 g (1/2 K), 1.8 g (1/4 K), 0.9 g (1/8 K) and 0.6 g (1/12 K), respectively. The total fruit yield decreased to about 75% at 1/2 K and 58% at 1/12 K compared to 1 K. The fruit K content was lower in 1/4 K, 1/8 K and 1/12 K than in 1 K and 1/2 K, and the fruit from 1/8 K and 1/12 K achieved below 100 mg 100 g−1 FW of K. Total soluble solid content (Brix) was 7–8% in 1 K and 1/4 K but was lower in 1/8 K and 1/12 K. Fruit acid content decreased to 87% in 1/2 K to 70% in 1/4 K and 1/8 K, and to 57% in 1/12 K of 1 K. In conclusion, quantitative K management in hydroponics is expected to produce low K tomato fruit. Fruit K content of approximately 100 mg.100 g−1 FW was achieved when the quantity of K supply was 1/4 K and 1/8 K, with a relatively smaller effect on fruit yield, Brix and acid content.

The low-node pinching order at a high-density plant cultivation system (LN&HD) is now widely adopted for increasing tomato yield and fruit quality. The LN&HD cultivation period spans 70–120 days, employs the use of a small amount of substrate (low substrate volume), and plants are usually topped between the first and the fourth truss. Using a small amount of substrate in cultivation induces root restriction. Increasing the extent of root restriction in small pots has been adopted for increasing the fruit quality of tomato in some advanced countries. However, improving fruit quality at the expense of yield becomes a major drawback for adopting the LN&HD in Ghana. The LN&HD was introduced into Ghana mainly to increase tomato yield sustainably at a cost-effective level. This study aimed to manipulate or reduce the extent of root restriction to increase tomato yield. Information related to manipulating or reducing the extent of root restriction has not been extensively reported. Thus, an experiment was conducted (between 21 April 2019 and 11 August 2019) in the greenhouse of the University of Ghana Forest and Horticultural Research Centre, Kade-Ghana. Plants of two tomato cultivars (Jaguar and Momotaro York) were subjected to four root restriction conditions. The extent of root restriction were (1) complete root restriction in a 1.0 L volume capacity pot, (2) complete root restriction in a 1.5 L volume capacity pot, (3) partial root restriction in Rockwool-like cultivation, otherwise referred to as Cocowool, and (4) No root restriction in a trough containing 1.5 L of the substrate. The experiment was laid out in a 2 x 4 factorial in a randomized complete block. Results showed that partial root restriction in Cocowool and unre-stricted roots in the trough produced the highest tomato yield and total dry matter compared to the plants that received complete root restrictions in the 1.0 and 1.5 L pots. However, the tomato’s total soluble solids increased with a complete root restriction in the 1.0 L pot. Reducing the extent of root restriction increased the yield and total dry matter of tomato. With the LN&HD, a small amount of substrate could be used (at a reduced cost) with a partial root restriction to increase the yield of tropical tomato cultivars grown in Ghana.

Recently, the number of patients with chronic kidney disease has increased rapidly and kidneys with loss of the K-defecating function have been observed. Thus, providing vegetables with low potassium is an urgent unmet need. In this study, two cultivation methods were used to cultivate lettuce (Lactuca sativa L.) with low K concentrations. One method, dubbed LKEC, was based on electrical conductance management and the K supply was stopped at the end of cultivation. The other method, dubbed LKQM, was based on nutrient quantitative management, and the nutrients required for low-K lettuce were quantitatively supplied. Meanwhile, control lettuce with a normal K concentration, known as CK, were cultivated with electrical conductance management. Compared with CK, both low K treatments reduced the yield by nearly 20% without any visual deficiency symptoms. There was no significant difference between LKEC and LKQM in terms of plant growth. LKQM-treated lettuce contained lower Na and required less fertilizer than LKEC lettuce. Moreover, these plants adapted to K deficiency stress by absorbing more cations to maintain osmotic pressure. N declined with decreasing K. This suggested that the quantitative management method in lowpotassium lettuce production reduced the potassium content in the lettuce plants to the same level as the EC management method, and significantly reduced the sodium content compared to EC management.

The issue of low tomato production in the tropics like Ghana has been a long‐standing challenge. The advent of greenhouse technology has not significantly improved the yield of tomato compared to Japan and the Netherlands. Immediate technological interventions are needed. Through hydroponics, the low‐node order pinching at a high‐density planting system has been recommended in some studies. This system was intended to be established in Ghana, and it would be expected to improve the yield and fruit quality of tomato. In effect, a study was carried out in the greenhouse, at Chiba University using this system. A tropical tomato cultivar (Jaguar) was evaluated with Momotaro York at 3.8 m s2 and pinched at the fourth truss. Data collected were water and nutrient use efficiencies, plant growth rate, dry matter partitioning, and fruit yield and quality, as well as some physiological characteristics. The experiment was laid out in a randomized complete block design with three replications. Results showed that Jaguar cultivar was two times more efficient in water and nutrient use than Momotaro York at first harvest. Root tissue density recorded in Jaguar was significantly lower compared to Momotaro York. The net assimilation rate (NAR) recorded was markedly higher in Jaguar than Momotaro York at last harvest. All the physiological attributes recorded in both cultivars were not significantly different. Plant dry mass (DM) recorded was similar in the two cultivars; however, the DM partitioned to fruits was 55% in Jaguar compared to 46.5% DM for Momotaro York. Fruit yield per area did not differ in the two cultivars. Fruit yields of 28.8 and 30 kg m−2 per year were recorded in Jaguar and Momotaro York, respectively. In comparison, this yield result is 1.2–1.25 times less and 14.4–15 times higher than current tomato yields recorded in Japan (greenhouse) and Ghana, respectively. Fruit quality, in terms of total soluble solids recorded in Jaguar cultivar being 5.4 %Brix, was within the 3.5–5.6 %Brix recorded in Ghana. This system could effectively enhance the yield and quality of tomato in the tropics as well as economising on the use of resources.

Plant factories or vertical farms with LED lighting have been developed to grow fresh and high-quality vegetables inside urban buildings without being restricted by climate and land. Environmental control technologies are developing rapidly for improving productivity of leafy vegetables in plant factories. However, tipburn issues are also rising with the increase of plant growth rate and this reduces the product quality and its marketable value. The tip-burned parts of the vegetable must be removed manually at harvest, which causes more yield loss and labor cost. In this research, the effects of light intensities with different total light integrals (TLI) or with the same TLI on lettuce growth and tipburn occurrence were investigated. In the first experiment, three light intensities: 85, 125, and 187 µmol m-2 s-1 were applied to the rapid growth stage of romaine lettuce plants and in the second experiment, an average light intensity of 150 µmol m-2 s-1 was applied in four different lighting patterns to the plants. The results show that plant biomass clearly increased with increases of light intensity (or TLI) but was not affected by different lighting patterns under the same TLI. Leaf areas were not significantly affected by different light intensities under the present experimental conditions, indicating that plants firstly expand leaf area (rather than increase thickness) to increase light interception when light intensity is low. Tipburn occurred during 23~26 days after sowing and its occurrence was positively correlated with light intensity and relative growth rate (RGR). Regression analysis indicated that there could be a key threshold value in RGR which induces tipburn. To control an RGR value lower than the threshold value during 23~26 days after sowing would be critical for limiting tipburn occurrence.

<p>In this study, we investigated the effect of salinity on photosynthesis and the distribution of photosynthates in the Japanese tomato (Solanum lycopersicum) cultivar 'CF Momotaro York' and the Dutch cultivar 'Endeavour'. Although significant differences were not observed in fresh yield among the cultivars, there were significant differences between the control and salinity in terms of fresh yield, total soluble solids, and titratable acid. The total dry weight in the Japanese cultivar was not affected by salinity, but the Dutch cultivar had lower total weight under salinity compared to the control. Regarding dry mass partitioning, the Japanese cultivar had a lower dry mass ratio of vegetative organs and a higher ratio of fruits than the Dutch cultivar. Salinity did not affect the photosynthetic rate in the Japanese cultivar, but did affect the Dutch cultivar, possibly due to water use efficiency. These results indicate that this Japanese cultivar has characteristics of efficient fruit production under a low node-order pinching and high-density planting system, even under salinity conditions.</p>

<p> In this study, we investigated the differences between the Japanese cultivar'CF Momotaro York'and the Dutch cultivar'Endeavour'regarding their morphological characteristics and fruit yield under the low-node order pinching and high-density planting system. Fresh fruit yield was not significantly different between both cultivars. While the Japanese cultivar had lower total dry weight, had higher distribution rate to fruit. The Dutch cultivar had a lower extinction coefficient and higher integrated solar radiation at fruit truss. It also had a higher fruit temperature and respiration rate than the Japanese cultivar. These results indicated that the lack of difference in yield between both cultivars and lower distribution ratio to fruit in the Dutch cultivar might be due to higher consumption of photoassimilate, which led to higher respiration rate and fruit temperature caused by higher extinction coefficient.</p>

Production of tomato in the tropics especially in Ghana is beset with lots of setbacks thereby causing low yields per hectare. Greenhouse cultivation systems are promising yet yields of tropical tomato cultivars are hampered by adverse temperature conditions. In order to mitigate this, an experiment was conducted during the extreme summer temperature conditions in the greenhouse at Kashiwanoha Campus of Chiba University, Japan. The study was conducted between May 23, 2018 and September20, 2018. The low substrate volume production system of 500mL in closed recirculated hydroponics (sub-irrigation) method was employed. Three tropical tomato cultivars (Jaguar, Lebombo and Lindo) were evaluated for yields. Plants were spaced at 20cm (4.2 plants m-2) and 30cm (2.8 plants m-2). At 7 and 9WAT, plants were topped at 2nd and 4th nodes respectively. The 3x2x2 factorial in Randomised Complete Block design in three replications was adopted. Some parameter collected were; 1. Morphometrics such as plant height, girth, leaf number and chlorophyll content, days to 50% flowering and fruit set 2. Yield components and fruit quality such as fruit number, marketable yield, yield per area, yield per hectare, percent blossom end rot, fruit TSS, TA, TSS/TA ratio and 3. Dry matter partitioning at last harvest, 11WAT. Results showed that blossom end rot reduced the yields of Jaguar and Lindo almost by 50% while Lebombo recorded less than 1%. Lebombo produced significantly the highest plant dry mass of 125g of which 57.7% was converted to vegetative growth compared to the Jaguar. For Jaguar however, 53.7% of total plant dry mass was allocated to fruits. This in effect was translated to the highest yield of 93tons ha-1 year-1 for Jaguar plants that were pinched at 4th truss in high density planting of 4.2 plant m-2.

Humans tend to ingest excessive amounts of fat and salt but fewer vegetables, exercise less and maintain more sedentary, inordinate-hours lifestyles. These lifestyles are causal factors in diseases called "lifestyle-related diseases". Especially, chronic kidney failure is becoming a global problem in recent years. In this study, a method of producing low-potassium (K) tomato fruit was investigated. Two medium-sized tomato (Solanum lycopersicum L.) cultivars 'Frutica' and 'Aichan' were used, and the K supply was restricted using hydroponic (NFT and rockwool culture) technique. Fruit weight was not affected by K restriction in both cultivars. As for K content in the fruit, 'Frutica' seemed to be more sensitive to K-deficient treatment than 'Aichan'. Under rockwool culture condition, fruit K content decreased to 62% by K restriction compared to control in 'Frutica', and to 72% in 'Aichan'. Soluble solid content of the fruit showed around 6% under both cultivars and both production systems except the fruits of 3rd truss in K-deficient treatment plot. Acid content of the fruit tended to decrease by K-deficient treatment, especially in 'Aichan' under rockwool culture. The difference between two cultivation systems may due to the difference of water status around the roots. In conclusion, control of K supply by hydroponics was effective to reduce the K content of tomato fruit. The most important problem is the decrease of acid content, and this might lead to the change of fruit taste. In addition, the effect of the treatment was not stable depending on the cultivation system. More precise technique to control K supply should be necessary to stabilize the yield and quality of low-K tomato fruit production.

The authors propose a new system for export of high-quality tomato fruit involving harvesting at the mature green stage and ripening in the importing country. In this study, the postharvest dynamics of tomato fruit quality from the mature green to red ripe stage were investigated. The harvested mature green fruit was ripened to the red ripe stage in an incubator at 20°C. After 2, 3, 5, 7, 10, 12 and 14 days of ripening, the fruit quality was investigated. The soluble solid content remained constant during ripening. The acidity, which was highest at harvest, decreased with ripening. The glucose and fructose contents, which were lowest at the start of ripening, increased at the early ripening stage and thereafter remained constant. There was no difference in the sucrose content during ripening. The chlorophyll and insoluble pectin contents were highest at the start of ripening and decreased with ripening, whereas the lycopene and soluble pectin contents drastically increased after ripening; chlorophyll disappeared completely at the end of ripening. The hardness also decreased with ripening. The dynamics of soluble solid content, acidity, sugars, chlorophyll, lycopene, β-carotene, firmness values, and pectin of postharvest-ripened fruit harvested at the mature green stage were consistent with those of fruit ripened on-tree. The total sugar concentration, SSC and acidity levels, which are important values for fruit quality and flavor, were the same as those of market fruit. Thus, the fruit quality and flavor of postharvest-ripened fruit harvested at the mature green stage were considered equal to those of on-tree ripened fruit.

Intensive crop cultivation in greenhouses results in insufficient light to plants, which decreases plant photosynthesis and growth and results in reduced crop productivity and reduced economic benefit. Foliar supplemental lighting to leaves in the lower canopy is considered an effective method to cope with the stress of insufficient light on plants. Leaf photosynthesis, stomatal regulation, and growth of tomato plants were examined to estimate the effect of supplemental lighting from underneath the canopy (USL) with light orientation to the abaxial side and from the inner canopy (ISL) with light orientation to the adaxial side. Both treatments significantly improved light irradiation conditions in the lower canopy and promoted growth and photosynthesis of tomato plants. USL maintains a relatively steady light irradiation level in the lower canopy and promotes better photosynthetic and morphologic enhancement than ISL. The improved photosynthesis in plants treated with ISL resulted from larger stomatal pore area and higher stomatal conductance which enhanced carbon dioxide supply promoting photosynthetic electron transport activity. Meanwhile, USL enhanced carbon dioxide assimilation efficiency rather than stomatal morphology regulation to improve plant photosynthesis.

In order to solve the problems of light insufficiency that occur in intensive greenhouse production, we applied far-red-wavelength introduced light-emitting diodes (LEDs) as supplemental lighting to the lower canopy of intensively cultivated tomato. To test the performance of this light source, we measured leaf photosynthesis, stomatal regulation, and plant development of tomato treated with or without supplemental lighting of deep red/blue (DR/B) and deep red/blue/far-red (DR/B/FR) LEDs. Leaf photosynthesis rate (Pn), transpiration rate (Tr) and stomatal conductance (Gs) increased significantly in plants treated with both supplemental lighting regimes, and the enhancement in the DR/B/FR treatment was greater than that in DR/B. Stomatal closure was reduced with treatment of supplemental lighting, while DR/B/FR introduced a larger stomatal pore area, stomatal density, and stomatal index compared with DR/B. Relative growth rate (RGR) and net assimilation rate (NAR) of plants treated with DR/B/FR were significantly higher, while the leaf area ratio (LAR) was higher in DR/B treatment. Though stem height decreased, plant dry weight and flower number were significantly increased by the application of supplemental lighting. Investigation of interspecific relationships between metabolism and morphology showed that Pn, Gs, RGR, NAR, stomatal pore area, root length and weight were all highly correlated (R2≈0.9), suggesting a close coupling of organ-level metabolism and whole-plant performance. These results reconfirmed the effectiveness on plant growth of supplemental lighting to cope with light insufficiency, and indicated that the introduced far-red- to red and blue-wavelength irradiation could intervene to prevent stomatal closure and promote root development to guarantee leaf photosynthesis and dry matter production, therefore enhancing plant growth and development under low light conditions.

Light insufficiency is a major abiotic stress limiting plant growth and crop yield in intensive greenhouse production. The application of supplemental lighting to the lower canopy is an efficient method to increase irradiation levels in greenhouse tomato cultivation systems. We evaluated the effects of supplemental lighting provided from underneath the canopy (USL) or within the inner canopy (ISL) on leaf photosynthetic traits, plant growth, and fruit development in single-truss tomato plants. Both USL and ISL significantly promoted leaf photosynthetic activities, plant growth, and fruit production in plants exposed to low solar irradiation levels. The use of USL maintained relatively stable light irradiation conditions in the lower canopy. It also promoted photosynthesis through improved CO2 assimilation and stomatal conductance, and contributed more to fruit yield than ISL. However, ISL induced greater increase in fruit soluble solid contents because of higher exposure to direct supplemental light to fruit. Based on physiological outputs and an energy cost performance analysis, the application of USL may be more financially viable than the use of ISL.

[Abstract] To investigate relationship between tomato （Solanum lycopersicum） leaf chlorophyll content and Minolta SPAD-502 plus chlorophyll meter, we studied leaves at plant vegetative growth stage and reproductive growth stage, and conducted correlation analysis to establish most optimal function model. The results showed that the correlation of SPAD value and the content of chlorophyll a, chlorophyll b and total chlorophyll content were significantly correlated in tomato leaves. At plant vegetative growth stage, the optimal mathematic function for SPAD value and chlorophyll a, chlorophyll b and total chlorophyll were y = 0.0006x 1.924 （ r = 0.785）, y = 0.0006 x1.8009 （ r = 0.756） and y = 0.2317e 0.0406x （ r = 0.869） respectively. At reproductive growth stage, the optimal function models were y = 0.0236x－0.0705（ r = 0.856） for chlorophyll a, y = 0.2975e 0.0127x （ r = 0.793） for chlorophyll b and y = 0.0306x + 0.1443（ r = 0.869） for total chlorophyll. All these data proved SPAD-502 can be an effective tool used for rapid and nondestructive estimation of leaf chlorophyll content in tomato.

Chronic kidney disease has become a major public health problem worldwide. The aim of this study was to investigate the differences in plant growth and photosynthesis among three lettuce (Lactuca sativa) types with different morphological characteristics under low potassium conditions, providing information for improving the method of low-potassium lettuce culture. Lettuce was hydroponically grown in half-strength Enshi formula nutrient solution containing 4, 2, or 1 me. L-1 K+. The plant yield and relative growth rates (RGR) of all three lettuce types were lowest under a treatment with 1 me. L-1 K+. In green leaf lettuce, reductions in both the net assimilate rate (NAR) and leaf area ratio (LAR) led to a decline in RGR. In Boston lettuce and romaine lettuce, the reduction of RGR was mainly due to a reduction in LAR, and to a lesser extent caused by NAR. Reduced potassium in the nutrient solution had a greater effect on mature leaves than on newly expanded leaves for all three lettuce types. In green leaf lettuce and Boston lettuce, photosynthetic rates of mature leaves significantly decreased under reduced potassium treatments, with a steady or gradually increased intercellular CO2 concentration; this indicated that non-stomatal factors suppressed photosynthesis. In romaine lettuce, the photosynthetic rate was less influenced by reduced potassium levels in the nutrient solution, and the significant increase observed in leaf mass per area might contribute to maintaining photosynthesis in the leaf. The decrease in photosynthesis in mature leaves exhibited a similar trend to the decreased potassium content in the leaves within the three lettuce types, but the factor related to the reduction of photosynthesis was different.

Tomato plants in greenhouse production are often confronted with light insufficiency in the lower canopy, especially in the winter low irradiation season. In this study, periodic alteration of plant density (PD) was proposed to improve the light environment of plants' lower canopies, leaf photosynthesis, plant growth, and fruit development. These were investigated with winter cultivated tomatoes in a single-truss production system. Seedlings were transplanted to either movable or fixed cultivation benches for treatments with fixed PDs of 14.3 plants . m(-2) (F14.3), and 10 plants . m(-2) (F10), and unfixed PDs in a movable bench (MB; 25 plants . m(-2) after transplanting to anthesis, 16.6 plants . m(-2) at anthesis to initial fruit set, 12.5 plants . m(-2) at fruit set to mature green, and 11.1 plants . m(-2) at mature green to red-ripe). The leaf photosynthesis rates in MB and F10 were generally significantly higher than in F14.3. F14.3 had the tallest stems, but the lowest leaf area and shoot dry weight at end of experiment, while MB and F10 were not significantly different. MB had significantly the highest total yield, while the lowest data were observed in F10. The soluble solids content was increased in MB and F10 compared with F14.3, but no significant differences in ascorbic acid content or fruit hardness were observed among treatments. Therefore, a high PD in the vegetative stage, but a relatively lower PD in the fruit development stage, was highly efficient in intensive tomato cultivation.

<p>手賀沼の富栄養化水を利用したヨウサイの養液栽培で水路に沈殿するSSを造粒し，園芸培地として有効利用できるかを検討した．SS培地のNO₃-N含有量は市販培地に比べて極めて少なかったが，交換性Mnは非常に高い値を示した．培地を好気発酵処理すると，SS培地のNO₃-N含有量は発酵処理温度30°Cで処理前に比べて顕著に増加し，さらに処理中の培地の水分量が少ない程高い値を示した．交換性および水溶性Mn含有量は，SS培地の30°C処理では処理前よりも高くなった．一方，SS培地とバーク堆肥を混合することで交換性および水溶性Mn含有量が低下し，30°C処理でも処理後の水溶性Mn含有量の増加は認められなかった．45°C条件では培地の水分量にかかわらず，いずれの培地でもMn含有量が30 mg・kg^–1以下となった．30°C処理のSS培地では，コマツナの初期生育が抑制されたが，それ以外の処理区では，コマツナの生育の差は比較的小さかった．以上，SS培地で栽培したコマツナの生育は市販の園芸培土での生育に及ばなかったが，SS培地とバーク堆肥の混合物を好気発酵処理することによって化学性が改善するため，園芸培土として利用できる可能性があり，未利用資源の活用や富栄養化湖沼水の浄化の一助となると考えられた．</p>

The Center for Environment, Health, and Field Sciences, Chiba University and the Japan Plant Factory Association are using five greenhouses (semi-closed system) with an environmental control system and three plant factories with artificial lighting (total 10,845m2) on the campus of Chiba University for research, education, and training. Annually, over 5000 people visit the facilities to learn about and understand plant factories. This education program on plant factories has been carried out since 2011 for the graduate school students of Chiba University and short-stay (70-90 days) students from sister universities. Intensive business forums on plant factories have been held since 2010, covering the information, science, business, and operation of plant factories. Intensive plant factory business workshops have been held on a wide range of issues for business people by planning workshops, excursions, and instructor dispatches on a monthly basis since 2009.

In soilless culture, all nutrients are supplied to the plants by nutrient solution sufficient to meet the plants' demands. The composition of the solution means the concentration of each nutrient ion in the solution. Many kinds of composition have been designed the composition should be chosen depending on the kind of plant, growth stage, target quality of the product, etc. Nevertheless, the only difference is the proportion of each ion and the concentration. In soilless culture, a slight change of nutrient management can greatly influence plant growth and the quality of the product. Therefore, a proper understanding of the nutrient solution is essential for successful plant cultivation even in artificial environments. In addition, a new concept of nutrient management, namely quantitative management, is described.

Swertia japonica Makino has been used as a traditional medicine for a long time in Japan. The aim of this study is to clarify the effect of cultivars, plant age and altitude of production site on swertiamarin content in S. japonica plants. The seedlings of 9 cultivars in the field, 5 cultivars in the field or pot and 3 cultivars in the field or pot were used for experiments 1, 2 and 3, respectively. In experiment 1, the effect of varietal difference on the content of swertiamarin was investigated. The content in 'S-117' and '15-Haya' was higher than that in the other cultivars. In experiment 2, the content of swertiamarin in one-year-old seedlings was compared with that in two-year-old ones. In the case of potted seedlings, the content of swertiamarin in two-year-old seedlings was higher than one-year-old ones in all cultivars except 'S-117'. In comparison between potted seedlings and those in field, however, the content in one-year-old potted ones in some cultivars was the same range or higher than that in two-year-old ones in field. In experiment 3, the content of swertiamarin in 3 cultivars cultivated on the altitude of 1,800 m (Sugadaira, Nagano), 815 m (Komoro, Nagano) and 20 m (Kashiwa, Chiba) was investigated. In field culture, 'Mimaki-2-go' and 'Mimaki-3-go' seedlings grown at Sugadaira showed significantly higher swertiamarin content than those at Komoro. In pot culture, the content in 'Mimaki-2-go' and 'Mimaki-3-go' seedlings grown at Komoro was significantly higher than in the seedlings grown at the other altitudes. © ISHS.

ピーマンでは栄養繁殖を前提として育成された品種の増殖を目的とした栄養繁殖法が報告されているが，株当たりの増殖効率が極めて低い．そこで，増殖効率の向上を目的として，母株の主茎摘心節位，側枝の腋芽残存数および培養液濃度が挿し穂採取数に及ぼす影響について検討した．その結果，母株を第8葉上で摘心し，一次側枝および二次側枝の腋芽2個が母株に残るように側枝を採取し，施肥量を多くすることで挿し穂の採取効率を大幅に向上できることを示した．また，得られた挿し穂の発根率は極めて高かった．

The present experiments were undertaken in order to clarify the effects of a high potassium fertilization level on the occurrence of viviparous sprouting in melon fruit. Melon (Cucumis melo L. group) plants of two susceptible lines and one resistant line to viviparous sprouting were used at two different potassium concentrations. A high potassium fertilization level (12.0 mmol.L-1) resulted in a marked decrease of the occurrence of viviparous sprouting in the susceptible lines, and in the increase of the endogenous ABA content. No significant differences were observed in the seed number per fruit, the seed weight, and the percentage of seed germination at a high level of potassium fertilization. Further experiments were conducted in order to analyze the effects of exogenous ABA treatment at a low potassium fertilization level (1.5 mmol.L-1) on the occurrence of viviparous sprouting in melon fruit. At 25 days after pollination, ABA solution at different concentrations was sprayed on the fruits of the susceptible melon line grown at two different potassium fertilization levels. Even at a low potassium fertilization level, exogenous ABA application inhibited the occurrence of viviparous sprouting and increased ABA contents both in juice samples around the placenta and in the seeds. ABA treatment, however, led to a significant decrease in the seed number per fruit and in the percentage of seed germination, as a result of a marked increase in the ABA content and potassium absorption.

生薬「柴胡」の基原植物であるミシマサイコについて, 養液栽培での施肥管理法確立を目的とし, 灌液する培養液のECと生育, サイコサポニン含有量, 植物体中の無機成分組成との関係について調査した. ミシマサイコの栽培は, PVCパイプを利用した循環式ロックウール耕で行った. 培養液は大塚B処方とし, 処理区は灌液する培養液濃度について0.6 dS m^-1 (1/4単位区), 1.2 dS m^-1 (1/2単位区), 2.4 dS m^-1 (1単位区)の3水準とした. 地上部の生育, 最大葉の葉面積および草丈は, 1単位区で他の区に比べて低下したが, 地下部乾物重には処理の影響がなかった. T/R比は1単位区で他の区より低かった. 乾物重当たりのサイコサポニン含有量には処理区間で差がなかったが, 株当たりのサイコサポニン収量は, 1単位区で最も高かった. 植物体中の無機成分濃度は, 概して1単位区で高い傾向があったが, 植物体中の無機成分の含有比はいずれの区も同様の傾向を示した. また, ミシマサイコに好適な培養液の無機成分組成はN：P：K：Ca：Mg＝6.5：4.7：8：1.3：1.8 me L^-1程度と考えられた.

千葉県手賀沼の富栄養化水のみを肥料源としたエンサイの水耕栽培において，水中の懸濁物質（SS）に着目し，エンサイの生育に及ぼす影響から，栽培に適した水路長および導入水の流速を検討した．その結果，水路に沈積したSSによりエンサイの生育は促進され，エンサイは水溶性の肥料成分のみならず，SSからも養分を吸収していることが明らかとなった．SSの沈殿特性は，湖沼水中のSS含有量や，導入水の流速により異なった．水路の上流から下流にかけて生育が均一で高い収量を得ることができ，且つ排水の水質がより改善された条件として，野菜生産と水質浄化の両面から，本実験の条件下では，水路長は20 mまでが好ましく，流す水量は10-20 L/minが最適であると考えられた．

The single truss tomato production system (STTPS) was used to grow tomato plants at a density of 14.3 plants·m⁻² for increasing the tomato yield in Japan. We applied supplemental lighting within the canopy at different tomato development stages to identify the most sensitive stage at which supplemental lighting will most effectively increase yield and quality of tomato fruits. Fluorescent lamps were used to supply intra-canopy lighting to tomato plants (5:00–21:00) during the stages of anthesis (stage 1), rapid fruit development (stage 2), fruit ripening (stage 3), and from initial anthesis to red-ripe fruit (whole stage), respectively. Supplemental lighting applied to tomato plants during stage 2 and whole stage significantly increased the yield and sugar content of tomato fruits. Moreover, the contribution of supplemental lighting to the daily increase of tomato yield was highest at stage 2. The increase of fruit fresh weight and amount of supplemental lighting showed positive linear relationship. Supplemental lighting did not affect the ascorbic acid content of tomato fruits, fruit number per plant, and plant shoot weight among all the treatments. Thus, based on economic advantage, the use of supplemental lighting during the rapid fruit development stage of tomato plants under STTPS was most efficient.

In the present study, we investigated the effects of supplemental lighting (SL) with white, red, and blue light-emitting diodes (LEDs) on the yield and quality of tomato grown under the single-truss tomato production system (STTPS). SL was applied for 28 days during the rapid fruit development stage. Based on the same power consumption, the light treatments with the white and red LEDs increased the fresh yield of tomato by 12 and 14%, and the dry yield by 16 and 14%, compared with the control (without SL), respectively. Based on the unit photons emitted, the white LEDs showed high efficiency as the red LEDs in increasing tomato yield, followed by the blue ones. The results were probably due to the white LEDs that contained more than 50% of green light characterized by high penetration into the canopy. The sugar and ascorbic acid contents were not affected by SL from the LEDs. These results indicated that the white and red LEDs were effective in enhancing tomato yield and, in particular, the white LEDs with a combination of red, blue, and abundent green light would be more suitable to the use of STTPS at a high plant density.

This study was carried out to clarify the effect of long-term frozen storage of Swertia japonica seeds on germination, yield and swertiamarin content of the seedlings. The seeds were successively collected in the conventional way from the year 1992 to 2003, and stored at -20℃ until the experiment was begun. The germination percentage differed among the seeds that were collected in different years, but there were no significant correlation between the percentage and the storage period. In addition, correlation between plant dry weight and seed storage period was not observed. Moreover, the seed storage period had no effect on swertiamarin content of the seedlings. Therefore, the seed viability of S. japonica can be maintained for at least 13 years by freezing without affecting dry matter yield or quality as a crude drug.

Three types of charcoal were evaluated as a soil conditioner. The charcoal was made from thinned Japanese cedar (Cryptomeria japonica D. Don), Moso bamboo (Phyllostachys heterocycla Matsum.), and pruned shoots of Japanese pear (Pyrus pyrifolia var. culta Rehd.). The charcoal amendment increased the soil exchangeable cations, but hardly affected the soil CEC. Top fresh weight of the third lettuce crop grown in the soil medium without charcoal amendment substantially decreased in comparison with that of the first crop. Although the first lettuce growth in the medium with charcoal was smaller than without charcoal, the lettuce growth in the second and third crop was more suppressed in the treatment without charcoal than with charcoal. Leaf nitrate content decreased with the charcoal amendment, especially when the pear shoot charcoal was used. NO3-N discharge was smaller from the soil medium with the bamboo or the pear shoot charcoal in the first crop. The bamboo charcoal amendment decreased the discharge in the second crop as well. Although this effect was not observed in the third crop, the total amounts of NO3-N discharge were lower in the treatments with both 0.3-1 cm and &lt;0.3 cm bamboo charcoal, and with 0.3-1 cm pear shoot charcoal. However, none of the soil medium with the cedar charcoal reduced NO3-N discharge in any cropping period. These results suggest that charcoal made from some forestry and agricultural wastes such as bamboo and pear shoots can be applicable for a soil conditioner to increase soil exchangeable cations, to reduce growth suppression in continuous cropping, and to decrease NO3-N discharge from soil.

オクラのイボ果発生に及ぼす朔果への細菌散布，副がく片接触および湿度の影響について検討した．イボの部分から細菌が検出されたが，細菌の果皮への散布はイボ果の発生に影響しなかった．副がく片を人為的に果皮に接触させると，イボ果率が増加した．殺菌剤の散布後に副がく片を接触させると，接触のみを行った場合に比べて，イボ果率が高くなった．そこで，殺菌剤散布と水散布を比較したところ，両者ともに高いイボ果率を示した．高湿度環境下では，副がく片接触を行わない場合でも，イボ果率が高かった．しかし，副がく片を除去すると，イボ果率は湿度環境にかかわらず顕著に低くなった．以上のことから，副がく片表面の毛じが果皮に接触することがイボ果発生の直接的な要因と考えられ，高湿度環境下で接触が助長される可能性も示唆された．<br>

主にハーブを用いた園芸作業の持つ療法的効果について，心理的指標である精神健康調査（GHQ）および気分プロフィール検査（POMS），生理的指標である唾液中コルチゾール濃度およびフリッカー値を用い，主観的および客観的に検証することを試みた．<br> GHQから，園芸作業による神経症症状の改善傾向が認められた．POMSから，園芸作業には緊張や不安，抑うつ感，疲労感，当惑などの一時的な負の感情を減少させる効果があることが明らかとなった．唾液中コルチゾール濃度は作業前に比べて作業後に低下し，作業によるストレスの緩和効果が認められた．フリッカー値の変化から，屋外での栽培作業は室内でのクラフト作業に比べて中枢性疲労の回復効果が大きい可能性が示唆された．<br> 以上より，園芸作業は神経症症状や一時的気分の改善に有効であった．また，唾液中コルチゾール濃度とフリッカー値によって，園芸作業がストレスや中枢性疲労の解消に効果的であることを客観的に判断できた．質問紙による主観的評価に，客観的評価指標を組み合わせることで，園芸作業の療法的効果を総合的に判断し，より効果的なプログラムの構築と普及に寄与できると考えられた．<br>

ホウレンソウの低硝酸化を目的とした養液土耕技術確立のため，日射比例型給液制御によるポット栽培を行い，基礎的データを得ることを目的にした．<br> 施肥量を一定とした場合，給液量の増加により生育は促進された．葉色は給液量の増加により薄くなった．可食部硝酸濃度は給液量の増加によって顕著に低下したが，栽培後期に下位葉が黄化した．そこで，給液量，施肥量ともに増加させたところ，予測吸水量，NO₃-N吸収量の1.2倍程度を施肥することで，生育が促進された．対照区（予測量通りの給液，施肥）と1.2倍区では，葉色，可食部硝酸濃度について差がなかった．施与窒素利用率は，給液量，施肥量が増加するほど低くなったが，本試験の範囲内では，いずれの給水量，施肥量でも，90％前後と高かった．<br> 以上の結果，給液量や硝酸施肥量を日射に応じて制御することで，ホウレンソウの低硝酸化や，高い施与窒素利用率による環境負荷軽減が可能であり，ホウレンソウの養液土耕における日射比例型制御の有効性が示唆された．<br>

養液土耕と日射比例型給液制御を組み合わせてホウレンソウを実際栽培規模で栽培し，生育・外観，硝酸濃度，肥料利用効率などに及ぼす影響を調査した．<br> 養液栽培によるホウレンソウの吸水量およびNO₃-N吸収量実測値から得た，日射あたり予測吸水量，NO₃-N吸収量の1.2倍程度を給液，硝酸施与することで，生育・外観は慣行の土耕と変わらなかった．1.2倍給液，NO₃-N施与の時，総施与量は土耕の約2分の1，肥料利用効率は80％以上となり，顕著な節肥効果が認められた．可食部硝酸濃度は，養液土耕により，土耕に比べて低下する傾向が認められた．また養液土耕では，収穫前数日間の施肥停止処理により，生育・外観に影響を与えず，硝酸濃度をさらに低下できる可能性が示唆された．<br>

We have developed a prototype system for 3D video distance education using satellite communications and IP multicasting. Our system is based on personal computers and software codecs. The system is inexpensive and flexible for various configurations because it utilizes software modules. Our system can be easily installed outdoors since it does not use special hardware to encode, decode, or transmit multimedia data. Testing of our system implemented between a horticulture farm and an indoor studio, approximately 140 km apart, showed that it effectively supports distance education between indoor and outdoor environments and that it provides an enhanced 3D educational environment. © 2005 IEEE.