Masahiko Tamaki

Screening of Twelve Plant Species for Phytoremediation of Petroleum Hydrocarbon-Contaminated Soil

Abstract Twelve plant species were screened for their phytoremediation ability for the cleanup of hydrocarbon-contaminated soil in Japanese environmental conditions. The plants were cultivated in a greenhouse for 141 days in 1/5000 a Wagner pots containing the experimental diesel-contaminated soil. During plant cultivation, the changes in the total petroleum hydrocarbon (TPH) concentration, soil dehydrogenase activity (DHA) and the number of aerobic bacteria were evaluated. The results of the screening experiment indicated that eight plant species (Italian ryegrass, sorghum, maize, alfalfa, Bermuda grass, rice, kudzu and beggar ticks) caused a more significant decrease in the TPH concentration in the planted diesel-contaminated soil than in the unplanted soil, and would be effective in the phytoremediation of petroleum hydrocarbon-contaminated soil in Japan. The TPH concentration was more closely related to the soil DHA than to the aerobic bacterial number. In this study we discussed the characteristics of the plants which are suitable for phytoremediation.

Removal of residual pesticides in vegetables using ozone microbubbles

The removal of fenitrothion (FT) pesticide residues from vegetables by immersion in ozone-microbubbled solution was demonstrated. FT-treated lettuce, cherry tomatoes, and strawberries were immersed in ozone-microbubbled, ozone-millibubbled, and dechlorinated water. After that the percentage of residual FT in the vegetables was determined. Residual FT was efficiently removed from lettuce by immersing it in ozone-microbubbled solution containing more than 1.0 ppm dissolved ozone, or continuously generated ozone-microbubbled solution containing 2.0 ppm dissolved ozone. Similarly, for cherry tomatoes and strawberries, the continuously generated ozone-microbubbled solution containing 2.0 ppm dissolved ozone was highly effective. These results showed that ozone microbubbles effectively removed residual pesticides not only from leafy vegetables but also from fruity vegetables.

Effects of ozone microbubble treatment on removal of residual pesticides and quality of persimmon leaves

This study investigated the effects of ozone microbubble (OMCB) treatment on the removal of residual fenitrothion (FT) and benomyl pesticides from red and green persimmon leaves, and also the treatment effect on the leaf colours, physical properties and flavour. The continuous bubbling OMCB treatment was more effective than the non-bubbling OMCB treatments at reducing the FT and benomyl agricultural pesticide residues from both the red and green persimmon leaves. Moreover, the bubbling OMCB treatment had no effect on the colour and pulling strength of the leaves. These results indicate that the treatment by bubbling OMCB is an extremely effective method for removing the residues of FT and benomyl in persimmon leaves and has relatively little effect on leaf quality characteristics.

Ozone Microbubble Treatment at Various Water Temperatures for the Removal of Residual Pesticides with Negligible Effects on the Physical Properties of Lettuce and Cherry Tomatoes

UNLABELLED In this study, the effects of ozone microbubbles (OMCB) treatment at various water temperatures on the removal of residual fenitrothion (FT) pesticides and on the physical properties of lettuce and cherry tomatoes was examined. The residual FT percentage in lettuce and cherry tomatoes was shown decreased by using higher water temperatures, particularly at 30 °C, resulting in a decrease within the range of 32% to 52%, after the 20-min treatment. In addition, bubbling OMCB treatment did not alter the color and pulling strength of lettuce and cherry tomatoes. These results indicate that bubbling OMCB treatment at 30 °C is a highly effective method for the removal of FT residues in lettuce and cherry tomatoes, with relatively little effect on crop quality. PRACTICAL APPLICATION The bubbling OMCB has a potential of reducing the FT reduces on vegetables with no adverse effect on the sensory quality of vegetables.

Hardness Distribution and Endosperm Structure on Polishing Characteristics of Brewer’s Rice Kernels

Abstract This study was designed to determine the effects of the hardness distribution and the endosperm structure on the polishing characteristics of brewer’s rice kernels. We used four brewer’s rice cultivars, Kairyo-omachi, Hattan-nishiki No. 1, Senbon-nishiki and Yamada-nishiki. The broken kernel ratios in Kairyo-omachi and Hattan-nishiki No. 1 were significantly higher than those in Senbon-nishiki and Yamada-nishiki. Vickers hardness (VH) values in white-core tissues in kernels differed among varieties, which were significantly lower in Kairyo-omachi and Hattan-nishiki No. 1. However, no varietal differences were observed in VH values in the peripheral translucent tissues surrounding the white-core tissues. The tissues along the dorsoventral axis were softer than those along the longitudinal axis of the kernels. The tissues on the ventral side were softer than those on the dorsal side. Scanning electron microscopy (SEM) observations revealed the presence of closely arranged compound starch granules and few varietal differences in the peripheral translucent tissues surrounding the white-core tissues. However, as compared with Yamada-nishiki and Senbon-nishiki, in Hattan-nishiki No. 1 and Kairyo-omachi, the starch granules were loosely packed and the airspaces between the starch granules were more numerous in the white-core tissues. A higher number of airspaces and less starch were present in the endosperm cells along the dorsoventral axis when compared with along the longitudinal axis and on the ventral side than on the dorsal side. The present study showed that polishing characteristics are closely related with the endosperm structure, which is characterized as the density of starch granules.

Screening of plants for phytoremediation of oil-contaminated soil

Several species of ornamental flowering plants were evaluated regarding their phytoremediation ability for the cleanup of oil-contaminated soil in Japanese environmental conditions. Thirty-three species of plants were grown in oil-contaminated soil, and Mimosa, Zinnia, Gazania, and cypress vine were selected for further assessment on the basis of their favorable initial growth. No significant difference was observed in the above-ground and under-ground dry matter weight of Gazania 180 days after sowing between contaminated and non-contaminated plots. However, the other 3 species of plants died by the 180th day, indicating that Gazania has an especially strong tolerance for oil-contaminated soil. The total petroleum hydrocarbon concentration of the soils in which the 4 species of plants were grown decreased by 45-49% by the 180th day. Compared to an irrigated plot, the dehydrogenase activity of the contaminated soil also increased significantly, indicating a phytoremediation effect by the 4 tested plants. Mimosa, Zinnia, and cypress vine all died by the 180th day after seeding, but the roots themselves became a source of nutrients for the soil microorganisms, which led to a phytoremediation effect by increase in the oil degradation activity. It has been indicated that Gazania is most appropriate for phytoremediation of oil-contaminated soil.

Effects of Adding a Chelator After Ozone Microbubble Generation on Nutrient Composition, Medium Sterility, and Plant Growth

The generation of ozone microbubbles (O3MB) is an effective means of sterilizing plant culture media against bacteria and pathogens; however, the use of O3MB can induce precipitation of metal ions from the medium, such as iron (Fe) and manganese (Mn), that are important to plant growth. Here, we evaluated whether addition of a chelator, either ethylenediaminetetraacetic acid (EDTA) or diethylenetriaminepentaacetic acid (DTPA), could prevent this side effect of O3MB sterilization. We compared nutrient composition, medium sterility, and plant growth after various treatments (0, 0.1, 0.01, 0.001, or 0.0001% (w/v) of EDTA and DTPA addition after O3MB generation). Metal chelators (EDTA and DTPA) are widely used in algal and plant growth solutions to maintain iron (Fe) solubility in hydroponic solutions, EDTA is used in agriculture to remove heavy metals from heavily contaminated soils and also as a plant fertilizer, and DTPA has a wide range of applications including removal of heavy metals from agricultural soils. Thus, the available evidence indicates that addition of a chelator after O3MB generation may prevent precipitation of oxidized Fe or Mn in a culture medium. The addition of a chelator resulted in a concentration-dependent reduction in precipitates and the maintenance of Fe and Mn concentrations in the medium. Although O3MB sterilization did not affect plant growth, the addition of a chelator at concentrations of 0.1, 0.01, or 0.001% (w/v) had a significant deleterious effect. However, at a concentration of 0.0001%, the chelator had no significant effect on plant growth but did result in the maintenance of a higher Fe and Mn concentration compared to the O3MB treated control. The addition of a chelator did not alter the sterilizing effects of O3MB. These results indicate that the addition of a chelator at a concentration of 0.0001% to an O3MB-sterilized culture medium enabled the retention of dissolved Fe and Mn without affecting plant growth. The use of O3MB, plus a chelator, is an effective disinfection method in hydroponic culture.

Relationship between the Starch Properties of White-Core Tissue and Polishing Characteristics in Brewers’ Rice Kernels

References The kernels of Hattan-nishiki No. 1 and Kairyo-omachi have larger air spaces in the white-core tissue and are broken easily during the process of polishing when compared with those of Senbon-nishiki and Yamada-nishiki. The polishing characteristics of brewers’ rice kernels are closely related with the structure of the white-core tissue of kernels. In this study, the varietal differences in the starch properties of white-core tissue of brewers’ rice kernels on polishing characteristics were studied. The starch properties were studied by rapid visco analysis (RVA) and differential scanning calorimetry (DSC); the amylose content of the rice flour of each variety was also analysed. No significant differences were observed in the amylose content among the four varieties. The two RVA parameters, peak viscosity and breakdown, were higher in Hattan-nishiki No. 1 and no significant differences were observed in them among Senbon-nishiki, Yamada-nishiki and Kairyo-omachi. The DSC parameters, gelatinization onset and peak and conclusion temperatures, were higher in Hattan-nishiki No. 1, lower in Senbon-nishiki and Yamada-nishiki, and intermediate between them in Kairyo-omachi. These results suggest that the polishing characteristics of brewers’ rice kernels are related with not only the endosperm structure but also the starch property of white-core tissue, except for Kairyo-omachi.

Effect of different microbubble generation methods on growth of Japanese mustard spinach

ABSTRACT To provide the necessary oxygen for plant growth, the effectiveness of different generating methods of microbubbles (MB), a gas-water circulation type or a pressurization type (pressurization treatment), was investigated by comparing the growth characteristics and morphological observation of Brassica campestris L. var. Komatsuna Matsum. The plant growth in the pressurization treatment were significantly less than those in the circulation treatment at 3 weeks after planting. In plants grown in the pressurization treatment, epidermal cell abrasion and plasmolysis, indicators of cell death, were observed in root tip cells at 3 weeks after planting. The growth inhibition of plant in the pressurization treatment is suggested to be related to the oxidization of Fe in the nutrient solution under super-saturated dissolved oxygen conditions, the generation of hydroxyl radicals from MB, the oxidization of the root tip cell membrane, and osmotic stress to the roots.

Effects of microbubble generation methods and dissolved oxygen concentrations on growth of Japanese mustard spinach in hydroponic culture

ABSTRACT The use of microbubbles (MB) can improve the oxygen supply to plants grown under the deep flow technique of hydroponic culture. In a previous study, we compared the growth of komatsuna (Brassica rapa L. perviridis, Japanese mustard spinach) plants grown under hydroponic culture with MB generated by the pressurisation (P) method and the gas-water circulation (G) method. Plant growth was significantly lower in the presence of the P-MB than the G-MB. In this study, we aimed to identify the factor(s) responsible for the poor growth of komatsuna plants in the presence of P-MB. At three weeks after planting, the growth of the P-MB plants was less than the growth of G-MP plants and controls, regardless of dissolved oxygen concentrations. Analysis of the root tips by transmission electron microscopy showed plasmolysis of the P-MB root tip cells but not of the G-MB and control root tips. Our results suggest that the growth inhibition of plants grown in the presence of P-MB is due to inhibition of water and nutrition absorption from root tip cells due to this plasmolysis. This is likely due to oxidisation of root tip cells by hydroxyl radicals generated by many fine MB and/or osmotic stresses caused by the MB.