Effects of low soil temperature on the growth and maintenance of Japanese white oak under the conditions of low light intensities (19 μmolm^-2s^-1) were investigated. Trees (Quercus myrsinaefolia Blume) were kept in environment controlled chambers during the experiment at the soil temperatures of 5°C and 25°C. The net photosynthetic rate, dark respiration rate, transpiration rate and stomatal conductance were affected by the soil temperature. The net photosynthetic rate at the soil temperature of 5°C was higher than at the soil temperature of 25°C. The dark respiration rate was lower in 5°C soil temperature treatment than that at 25°C soil temperature. The higher net assimilation rate at the 5°C soil temperature was regarded as one of the reasons of the longer life of indoor trees under the lower soil temperature conditions.

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To evaluate problems that might affect the wet oxidation waste treatment system used in a closed ecology experiment facilities (CEEF), we ran a pilot unit and investigated the elution of various elements from and the deterioration of the catalyst and filtering material used for wet oxidation. It was ascertained that the catalyst contains not only Ti and Ru but also Na and S which act as binders when the catalyst is formed into a shape. Ru and S were detected in the first run at high concentrations, but in subsequent runs their concentrations rapidly decreased, and after several runs, they ceased to be detected. Na was detected in the first run at an extremely high concentration (450 ppm), and as the test continued, its dissolution gradually diminished but not to zero. We estimated that the dissolution of Na from the wet oxidation system used in the CEEF could be 3.5 times greater than that from the pilot unit. This raises concerns about damage caused by excessive Na to the plants cultivation. These results suggest that, when the catalyst is replaced, the wet oxidation system should be run idle at least several times to reduce the Na concentration: a simple way to monitor changes in Na concentration would be to measure changes in electrical conductivity (EC). After the pilot unit was run 20 times, the surface of the catalyst was found to be smooth, but there was no change in the decomposition efficiency of the unit. As the test was continued, however, we observed that Fe and Si that were contained in the inedible part of rice adhered to the catalyst surface. This suggests that, with the elapse of time, Fe and Si would accumulate and cover the catalyst surface, eventually reducing its decomposition efficiency. Lower carbonic acids would therefore remain undecomposed in the waste solution. Therefore, it is important to examine the method for preventing the deterioration of the catalyst.

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