This research investigated the feasibility of witloof chicory production with fermentation heat of cow’s manure, in Hokkaido, during semi-cold and cold seasons. Forcing culture experiments were conducted in semi-cold season (once, April to May, 2013) and cold season (twice, March, 2014; March, 2015). In each experiment, cow compost produced through a solid-liquid separator (water content; 72.6%) was used as heat sources. Temperature of outside air, indoor air, compost container, forcing chambers (soil and air) and heat exchangers were recorded. Through all experiments, compost temperature was maintained up to 30°C, and it showed potential to be used as a heat source for chicory forcing culture. In semi-cold season, temperatures of forcing chambers (6.3×0.9×0.65 m) were maintained stably, and average air temperature of forcing chamber reached 17.2°C in average, and marketable etiolated heads (Chicon) were obtained after 22 d. In cold season, air temperature of forcing chamber (3.0×0.9×0.65 m) was maintained stably (10.6°C in 2014, 14.4°C in 2015, in average), and marketable heads were obtained after 15 to 19 d. The results indicated that witloof chicory forcing culture in semi-cold and cold seasons by using cow manure fermentation heat as heat sources is indeed possible.

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This study investigates the effects of constant red and blue LED light on the growth and spine occurrence of daughter cladodes in edible Opuntia. Opuntia cladodes were grown by hydroponic culture using the deep flow technique under red, blue, and simultaneous irradiation with red and blue light. Daughter cladodes developed from mother cladodes in all treatments, thus indicating that edible Opuntia can be grown under constant light and hydroponics culture. The speed of elongation growth of first cladodes was lower under blue light than with other treatments. The number of daughter cladodes was also the lowest in cladodes under blue light and was the highest in cladodes under red light. Thus, compared with red light, blue light appears to suppress daughter cladode development. The number of spines, an undesirable characteristic of edible cacti, was the highest on cladodes under simultaneous irradiation with red and blue light. Daughter cladodes under blue light had more spines than those under red light. Our results show that light wavelength strongly affects daughter cladode growth and spine number. Thus, controlling the light environment is important for improving edible cactus growth and quality.

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The optimal design of air currents in greenhouses primarily requires a better insight into convective exchange between leaves and the environment via the leaf boundary layer. The objectives of this study were to establish a method for continuous and multipoint determination of leaf boundary layer conductance (G _A) in a tomato canopy within a greenhouse, and to evaluate the convective effect of circulating fans on the air currents in the tomato canopy based on vertical and horizontal profiles of G _A. The operation of circulating fans changed the direction and velocity of air currents by mixing the air in the greenhouse, which reduced vertical differences of air temperature in the tomato canopy. Furthermore, convective exchange between leaves and the environment was significantly enhanced via increases in G _A. However, the vertical and horizontal distributions of G _A were dependent on the locations of the circulating fans. In particular, the circulating fans set above the canopy resulted in remarkably higher G _A in the upper canopy. This approach to profiling the spatial distribution of G _A can contribute to the optimal design of air currents for efficient environmental control in greenhouses.

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In order to analyze the multiple effects of CO ₂ enrichment and humidification on leaf gas exchanges (photosynthetic rate, transpiration rate, and stomatal conductance) in sweet pepper plant and their dependence on the time of day, we measured the steady-state leaf gas exchanges under different CO ₂ concentrations (400 and 1000 μmol mol ⁻¹) and relative humidities (20, 40, and 60%) in the morning (0900–1130) and afternoon (1230–1500) periods. Increasing CO ₂ concentration significantly increased the photosynthetic rate but decreased transpiration rate and stomatal conductance during the both periods. Increasing relative humidity also significantly increased the photosynthetic rate due to improved stomatal conductance at both CO ₂ concentrations in the morning. In the afternoon, a similar pattern was observed only at the lower CO ₂ concentration, but not at the higher CO ₂ concentration because stomatal conductance was extremely low. These results suggest that both CO ₂ enrichment and humidification in greenhouses would be effective in the morning; however, in the afternoon, humidification would have little effect under CO ₂ enrichment condition, during which photosynthesis was improved but stomata were almost closed.

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We investigated the time-course pattern of electrolyte leakage from the root flesh of growing tuberous roots of two sweetpotato cultivars, Koganesengan and Narutokintoki, after exposing them to high temperature for short duration. For both cultivars, the electrolyte leakage after 1 h of treatment was significantly higher than that at 24 h after treatment. This pattern was similar to the pattern observed following instantaneous flooding treatment previously reported by us. Electrolyte leakage from plant cells is an indicator of cellular responses to various stress factors. Similar stress, therefore, might be caused in heated and flooded tuberous roots.

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