The root of Chinese licorice (Glycyrrhiza uralensis) is used worldwide as a medicinal herb. The goal of this study was to understand changes in the concentrations and compositions of four medicinal compounds—glycyrrhizic acid (GL), liquiritin (LQ), liquiritigenin (LG), and isoliquiritigenin (ISLG)—in the root of Chinese licorice during post-harvest treatment. The effects of post-harvest storage temperatures (−80, −30, −13, 4, and 25°C) and drying temperatures (30, 40, 50, and 60°C) on concentrations of the four medicinal compounds were investigated. GL and LQ concentrations in roots stored at −30 and −13°C for 1–2 weeks tended to be 4% to 13% higher than GL and LQ concentrations in roots dried directly in a vacuum freeze dryer (controls). LG concentrations in roots stored at 4°C for 2 weeks were nearly 60-fold higher and ISLG concentrations at 25°C for 1 week were 10-fold higher than LG and ISLG concentrations in the controls. In addition, low temperature (30 and 40°C) drying compared to vacuum freeze drying (controls) increased LG and ISLG concentrations without decreasing GL and LQ concentrations. This study provided an approach to increase the target compound concentrations in Chinese licorice for different market demands (drugs, cosmetics, and food).

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Roses are the most economically important ornamental crops produced throughout the world. Powdery mildew caused by Podosphaera pannosa is a major disease of greenhouse roses, and chemical fungicides are absolutely necessary for disease control. Ultraviolet (UV) in solar radiation has been thought to contribute to plant resistance against pathogens and herbivores. Here, we show that supplementary radiation with low levels of UV suppresses the development of powdery mildew disease in greenhouse roses. Supplemental UV radiation with a UV-B fluorescent lamp during the night was more effective than in the daytime. Gene expression analysis revealed that genes involved in secondary metabolic pathways were induced in rose plants by low levels of UV radiation. Direct exposure to UV radiation inhibited rose powdery mildew conidial germination in a dose-dependent manner. These results suggest that UV radiation can suppress powdery mildew development through inhibition of fungal growth and activation of host defenses. Disease control using supplemental UV radiation will contribute to reducing the environmental burdens from fungicide use.

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This work was undertaken to estimate the hydraulic properties of roots of tissue-cultured soybean (Glycine max [L.] Merr.) subject to stress gradients from varying concentrations of nutrient salts, sugar, and heavy metals (Zn, Cu, Mn, Hg) in the culture solution. Using the paper wick method, we varied the water potential of the culture media from −0.04 to −1.45 MPa. Growth was inhibited as increasing concentration of salt or sucrose, and zinc, copper, manganese and mercury in the culture solution, and the root growth was associated with the magnitude of the growth-induced water potential and hydraulic conductance, although the degree of inhibition at a given concentration differed among individual heavy metal ions. In the zone of elongation, turgor was kept larger than 0.3 MPa under all stress conditions, and thus, the cell volume was kept almost unchanged, indicating that osmotic adjustment was occurring according to rates of water inflow associated with cell expansion.

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From the viewpoint of conservation-oriented agriculture, a closed soilless cultivation using an organic substrate is desirable. We found that photocatalytic treatment efficiently decomposed phytotoxic compounds from rice hull, and the growth and yield of tomatoes in a closed system with the treatment were superior to a system without it. To enhance disease control in the system, this study investigated the suppression of bacterial wilt disease in a simulated waste nutrient solution with photocatalytic and silver treatments. The untreated waste nutrient solution had a high total organic carbon (TOC) concentration, and silver in the untreated solution had no antibacterial activity. By contrast, silver in the photocatalytically treated solution showed a high antibacterial effect via the low TOC of the treated solution. A similar trend of disease onset was observed when pathogenic bacteria were inoculated into the solutions used to cultivate tomato seedlings. These results suggest that, even if the concentration of organic species in waste nutrient solution from a closed system is high, lowering the TOC by photocatalytic treatment promotes the suppression of bacterial wilt disease through the antibacterial activity of silver. It is anticipated that combining photocatalytic and silver treatments will help to stabilize crop production in closed soilless cultivation.

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It is valuable for the control of water quality in lakes to grasp the global functional relationship between phytoplankton biomass (Chlorophyll-a; Chl-a), total phosphorous (TP) and total nitrogen (TN) in lake ecosystems. This paper aims at developing a comprehensive model that explains the relationship between Chl-a, TP and TN in lakes under a wide range of environments. Three regression models, the conventional Ordinary Least Squares (OLS) model, random effect panel model and dynamic panel model are compared. Estimation based on water quality data from 396 lakes in 18 European countries reveals that OLS estimation gives comparable parameters to those of many earlier studies, in which both TP and TN are significant determinants of Chl-a. Application of the non-conventional estimation methods alters this parameter structure radically. Station-specific effects being controlled, TN/TP is not a significant factor. The inclusion of auto-regressive effects makes TN insignificant. These results suggest that the concentration of Chl-a could be controlled by reducing the concentration of TP, rather than TN, the effect of which might however be offset by the past concentration of Chl-a. These models were tested by applying them to simulate the relationship for 9 Japanese lakes to show the superior performance of the non-conventional dynamic model.

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It has been proposed that cold acclimatization of the plant body enhances the nutritional value of leaf vegetables; however, little is known about the optimal duration of cooling required to enhance the quality of factory-processed vegetables. The ideal low temperature acclimatization period increases ascorbic acid and sugar content without increasing the nitrate ion concentration for a given root area. Here, we investigated the ascorbic acid and sugar contents in spinach with a given root area subject to chilling for different durations; 2, 4, 5, 6, and 7 days. Ascorbic acid and sugar content levels remained stable at the beginning of chilling; however, after 6 days, the levels of both parameters doubled compared to those in the control (no chilling). In comparison, nitrate ion concentration gradually decreased with increasing acclimatization period. Spinach plants acclimatized for 7 days showed similar results as those acclimatized for 6 days. Our results show that the optimal duration for root area chilling to produce high quality spinach is 6 days, when controlling the temperature of the nutrient solution under plant factory conditions.

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This research was conducted to study gas transfer in three cultivars of Japanese pear based on their actual geometry obtained from a 3D Laser Scanner. Gas diffusivity and skin resistance to gas diffusion found to be dependent on the cultivar. Gas diffusivity for ethane was found to be 8.10±1.2, 3.67±0.11 and 5.97±0.42 (×10⁻⁸ m² s⁻¹) for Kosui, Niitaka and Oushuu, respectively. Niitaka was found to have the highest skin resistance due to a noticeably lower number of lenticels on the skin. As expected gas diffusivity increased with increasing of temperature while skin resistance decreased. It was found that the diffusivity of CO₂ is much lower than O₂. The model was validated by conducting experiments to measure the internal concentration at different points of the fruit and comparing them with model results. The model was shown to be successful in predicting the internal gas concentrations.

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The effects of NaCl salinity and low solution temperature on the leaf wilting and transpiration rate of snap bean (Phaseolus vulgaris L.) plantlets grown hydroponically were examined. The image of a plant was recorded every 5 min after the start of the treatment. From the plant images, leaf curling could be detected almost unambiguously by the human eye. The decline in leaf blades was evaluated by the relative change in the y coordinate of the center of gravity of the leaf region in a plant image (wilting index). The response of the wilting index to salinity was close to that of transpiration rate and continuous. The ratio of plants with curled leaves was the most sensitive indicator of plant response to stresses in the range of 50 to 100 mM NaCl. Its response was close to all-or-none. It showed a marked interaction of the effects of salinity shock and temperature shock of the nutrient solution. Combined with 60 mM NaCl, solution temperature even at 20°C caused marked leaf curling whereas 60 mM NaCl combined with solution temperature at 25°C did not cause leaf curling.

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Production technologies using closed-type plant production systems have been studied to assess their suitability for stable and uniform expression of biopharmaceutical materials in transgenic plants. We have developed a production system for a veterinary vaccine candidate against swine edema disease, using transgenic plants. In this paper, we report the combined effects of plant cultivation density and light intensity on the production levels of a vaccine candidate, the double repeated B subunit of Shiga toxin 2e (2×Stx2eB), in transgenic lettuce cultivated in a closed-type plant factory. Leaf dry-matter yield and total soluble protein (TSP) yield increased at higher plant cultivation densities, but in contrast, the 2×Stx2eB concentration in the plants tended to decrease with an increase in plant cultivation density, so that the 2×Stx2eB yield per unit area at lower plant cultivation density (44.4 plants m⁻²) was similar to or even higher than that obtained at the highest plant density (222.2 plants m⁻²). In addition, at the cultivation density (44.4 plants m⁻²), a photosynthesis photon flux density (PPFD) 200 (200±50 μmol m⁻² s⁻¹) was optimal in terms of maximizing the 2×Stx2eB yield and minimizing the electrical consumption of lighting. These results show that an optimal combination of plant cultivation density and light intensity is important in improving the productivity of recombinant protein expression systems in transgenic lettuce leaves when grown in a plant factory.

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The wetting of plants due to guttation (i.e., drops of xylem sap that exude onto the leaves) represents a potential risk for incidence and outbreak of pathogens. Here, we investigated the effect of air circulation on guttation of tomato leaves under dark and high humidity conditions. The tomato plants were grown in a container and pinched above the second truss and were then separately placed in a darkened and constantly humidified growth cabinet that was exposed to three levels of air circulation intensity (air velocities of 0.05 m s⁻¹, 0.16 m s⁻¹, and ＞0.29 m s⁻¹). The evaporation rate increased in direct proportion to air velocity around the plants regardless of differences in leaf area. The guttation rate varied with leaf area; specially, tomato plants with small leaf areas secreted larger amounts of guttation water than those with large leaf areas. However, guttation was completely suppressed in both large and small leaves under well-circulated conditions (i.e., a velocity of >0.3 m s⁻¹). This study indicates that air circulation reduces the wetting of plants by guttation under dark and high humidity conditions, which is likely to suppress the secondary spread of pathogens.

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