Under non-fatal levels of stress, plants can produce high concentrations of sugars, functional proteins, antioxidants, and other beneficial metabolites. Reactive oxygen species (ROS) are present in all plants as cytotoxic metabolites and as mediators of stress responses. This study investigated the effects on the growth response of hydroponically grown Lactuca sativa L. ‘Red Fire' seedlings, after treatment with an ROS, hydrogen peroxide (H2O2), for 20 days. Treatment with 1.0 mM H2O2 significantly decreased growth and increased the anthocyanin content. In contrast, 0.1 mM H2O2 treatment significantly increased growth, changed the root morphology, and increased water absorption. H2O2 treatment induced endogenous H2O2 production within 1 to 3 h, but 0.1 mM H2O2 treatment gradually decreased the endogenous H2O2 concentration. On the other hand, H2O2 was maintained at high concentrations in leaves under 1.0 mM H2O2 treatment. These results suggest that a rapid increase in oxidative stress and quick reduction in the H2O2 content would be important factors for inducing high growth rate in leaf lettuce via H2O2 treatment at an appropriate concentration. Exposure to H2O2 or oxidative stress might be a successful strategy for efficient lettuce cultivation.
A simple and economical preparation of a titanium dioxide (TiO2)-coating solution by hydrothermal reaction was investigated. An aqueous solution of hydrogen peroxide mixed with TiO2 fine particles (Degussa P25) was autoclaved at 105–120 °C for 10–40 min, so that the solubility of TiO2 was found to be significantly improved at 120 °C and over and to greatly affect both the amount of TiO2 loaded on activated carbon (AC) particles and the stability of an AC-supported TiO2 film. As a result, the optimal preparation condition was determined to be 120 °C for the temperature and 40 min for the reaction time. The coating solution provided AC particles completely covered with a thin TiO2 film (TiO2/AC particles). An 1-m3 air contaminated with toluene at 1ppm (0.04 mmol m–3) in a reactor with an annular path packed with TiO2/AC particles revealed that toluene is quickly decomposed to below an undetectable concentration of 0.03 ppm and completely converted to CO2. This rate of decomposition was almost the same as that by TiO2/AC particles prepared using a commercially available coating solution, indicating that the coating solution prepared in the present study is useful.
During the winter season, greenhouse crops are exposed to insufficient light conditions because of lower solar radiation and sometimes the shadow of surrounding structures. In a strawberry greenhouse which was partly affected by the shadow of a neighboring structure, we investigated light conditions and effects of supplemental lighting with LEDs on the strawberry. Plots of three treatments were set in the greenhouse: 1) Shadow treatment, crops were exposed to the shadow until about 10:00; 2) LED treatment, crops were supplementally lighted with LEDs when the shadow occurred, and 3) No-Shadow treatment, crops were not exposed to the shadow. On sunny days, daily integrated photosynthetic photon flux density (PPFD) was decreased by approximately 5-10% in the Shadow treatment than the No-Shadow treatment and increased by approximately 10-20% in the LED treatment than the Shadow treatment. For the entire experimental period, however, decrease in cumulative PPFD in the Shadow treatment was smaller (approximately 5%), because 74% of the period were cloudy days with the smaller effect of the shadow. Light-photosynthesis curves and leaf area did not show significant differences among the treatments. Therefore, the photosynthesis per plant was considered to depend on light conditions in the respective treatments and was significantly improved in the LED treatment. Furthermore, the LED treatment improved flowering and fruit harvesting, while they were small in both of the Shadow treatment and the No Shadow treatment because of the cloudy weather in winter season. Thus, in the cloudy weather in winter, the negative effects of the shadow on strawberry crops appear relatively small and the supplemental lighting with LEDs can be expected to improve strawberry yield.
In recent years, an increasing emphasis on conserving biodiversity in cultivated land has led to a need for environmentally friendly and sustainable agriculture that does not depend on the excessive use of agrochemicals. However, it can be difficult to generate high crop yields without using herbicides because alternative methods of restricting weed growth are often costly and labor-intensive. Here, we designed a mesocosm to examine the weeding efficacy of a cheap, commercially available, automatic robot ball, which was originally designed for house cleaning. The weeding robot performed very well, particularly for sprouts of Monochoria vaginalis var. plantaginea, a major paddy weed found in central Japan.
In September 2016, Elon Musk's SpaceX presented an Interplanetary Transport System consisting of a spaceship and rockets to be used to colonize Mars. Space development by private organizations may commence in the near future. This paper summarizes an overview of simulation studies for space habitation and life support systems conducted by public and private organizations in facilities around the world, such as BIOS3, Biosphere 2, and Closed Ecology Experiment Facilities (CEEF). In addition, this paper describes the author's own simulation study and analog study regarding space habitation and life support systems. The computer simulation study was conducted to analyze mass flow inside CEEF. The analog simulation study was conducted at Mars Desert Research Station (MDRS) to know space habitation problems. The analog simulation study includes research on human metabolism, food science, and food production as well as an analog Extravehicular Activity (EVA) study similar to the MIT Haughton Mars Project conducted at Haughton Island. Finally, issues regarding design of a habitation system, a life support system, biomedical measurement system for keeping a crew healthy, EVA equipment, and an EVA navigation system on a planetary surface are compared with previous research conducted by other crews at the MDRS in the past.