Concentration of sulforaphane in broccoli is known to be enhanced during storage under an atmosphere of low O2 (0.002–1.3％) and high CO2 (20.6–25.4％). However, maintaining this concentration at a maximum is problematic. Therefore, storage of broccoli florets at low temperatures was investigated. Results showed that storage for 2 days under hypoxia significantly increased (3.3-fold against initial value) sulforaphane concentration. Subsequently, 4 days storage at three temperature levels was conducted. Sulforaphane levels were not maintained at 20℃ (normal temperature) or 1℃ (cold temperature). However, after storage at -20℃ (frozen) for 4 days, the sulforaphane concentration was not significantly reduced compared with the maximum level on day 2. Meanwhile, this concentration was not significantly higher than those at 20℃ or 1℃ on the same day. Storage under hypoxic conditions is known to affect the flavor and taste of vegetables. Therefore, eight taste factors were objectively measured using an electronic tongue. Astringency and bitterness were stable and independent of storage period and temperature, while other tastes were significantly affected by storage period. The rich umami value at -20℃ was significantly higher than that at 20℃, and in general it was challenging to maintain taste values even for cold or frozen storage.
The accurate determination of gas fluxes in soil-plant-atmosphere systems is crucial for various physio-ecological investigations. The closed chamber method estimates gas fluxes from vegetation and soil by the rate of change in gas concentrations, that is, the first derivatives of the regression functions fit to the measured change in gas concentration. Conventional regression functions, however, can underestimate the actual gas fluxes because these functions do not consider the dynamic characteristics of the concentration sensor (i.e., response lag and dead time). The purpose of this study is to develop a new regression function that can consider the dynamic characteristics of a gas concentration sensor. The newly proposed function was derived theoretically by solving a differential equation of a first-order lag relation between the sensor output and actual gas concentration inside a chamber. Its validity was examined by comparative analysis using CO2 concentration change measured by slow and rapid-response sensors. The newly proposed function improved the accuracy of flux estimation considerably when applied to the output of a slow-response sensor. The newly proposed function provides a method to evaluate gas fluxes using a low-cost, slow-response sensor in a closed chamber system with acceptable accuracy.
A soil-culture study was conducted to investigate the phytoextraction of cadmium (Cd) (20, 60, and 100 mg/kg) in two species of upland and lowland vetiver grass (Vetiveria nemoralis and V. zizanioides) with salinity levels of 1,000 mg/kg NaCl salt for 2 months. The two species of grass were highly tolerant to Cd and salt with little adverse effect on growth. Cd and salt treatments imposed significant negative effects on root length, shoot height and total dry biomass. Cd accumulation in the roots and shoots all increased significantly with increasing Cd concentration. The combined treatments of Cd and salt showed the highest root Cd accumulation in V. nemoralis (226―862 mg/kg) at Cd concentrations ranging from 20 to 100 mg/kg. Salt did not affect the accumulation of Cd but decreased the root-to-shoot Cd translocation. This was confirmed by the bioconcentration factor in root ＞ 1 and the translocation factor ＜ 1, which indicated the plant's suitability for phytostabilization of Cd under saline conditions. The experiment pointed out that V. nemoralis was a better accumulator of Cd than V. zizanioides.
Hydroponic culture holds potential advantages for the production of edible cacti, though there have been few studies investigating the effects on growth. This research investigates the effects of cultivation conditions including mother cladode size, fertilizer concentration and temperature on the growth of the edible cactus Nopalea cochenillifera in hydroponic culture. Mother cladode size was positively correlated with daughter cladode growth and development. Total fresh weight of daughter cladodes per mother cladode was highest when a large mother cladode was used, while small mother cladodes produced fewer daughter cladodes. Fertilizer usage was effective in promoting daughter cladode growth and development, though there was little difference in cladode number and length of first daughter cladode among different fertilizer treatments. In addition, we evaluated the effects of cultivation temperature (light and dark period temperatures of 25℃/15℃, 25℃/25℃, 35℃/15℃, 35℃/25℃, and 45℃/15℃). Cladode growth was promoted at 35℃/15℃ and 35℃/25℃ leading to an increased harvest of daughter cladodes compared with other treatments. Our results show that mother cladode size, fertilizer concentration and cultivation temperature strongly affect daughter cladode growth and development. Thus, controlling cultivation conditions is important for improving edible cactus productivity and quality when using hydroponics.
Medicinal plants are potential sources of secondary metabolites which may possess allelopathic properties. Hence, we investigated the allelopathic potential of 12 Thai medicinal plants against the growth of cress and barnyard grass. The 12 medicinal plant extracts showed a significant inhibition on the growth of those test plants. The inhibitory potentials depended on the extract concentration and test plant species. Comparing the average growth inhibition, the extracts from Crateva adansonii strongly inhibited the cress shoots and roots (96.0 and 95.6％), followed by Phlogacanthus pulcherrimus (93.1 and 93.4％), and Cuscuta chinensis (92.3 and 91.5％). Meanwhile, the barnyard grass shoots and roots were strongly inhibited by the extracts of P. pulcherrimus (88.2 and 97.6％), C. chinensis (73.7 and 82.3％), and Acanthopanax trifoliatus (73.0 and 94.3％). However, P. pulcherrimus extracts had a high allelopathic potential against both test plants, suggesting that P. pulcherrimus may be a potential candidate for purification of allelochemicals.
The medicinal plant Pinellia ternata Breit., which is a non-domesticated plant, is widely distributed in Japan. However, the crude drug made from the plant corm is not currently produced in Japan. We investigated the influences of air temperature on the growth of P. ternata collected from 2 regions, the Kyoto and Nagasaki prefectures, for both of summer and winter seasons. The temperature effects on the effective ingredient contents in the corms were also investigated. At Kyushu University, plants were grown for 15 weeks in phytotron glass rooms controlled at air temperatures of 20, 25, or 30℃. The corm yields and effective ingredient content in the winter cultivation were poorer than those in the summer, because the cumulative solar radiation during the winter cultivation period was almost half of that in the summer. In the Kyoto lines, the highest corm yield was obtained at 25℃ in the summer cultivation, while the Nagasaki lines did not show significant differences with respect to yield among the three growth temperature conditions. The effective ingredient contents in the corm did not differ significantly among the three temperature conditions for both lines, although the amount of effective ingredient in the Kyoto lines were significantly higher than those of Nagasaki in summer cultivation.