Distribution of Essential Elements in Brown Rice

Because the main pathway for elements intake by humans is through food ingestion, it is very important to understand the transfer of elements from soil to the food crops and the distribution of elements in the crops. The concentrations of elements in plant such as Ca and K vary significantly among the different plant organs. Since rice is a staple food in most Asian countries, rice grains are important to be evaluated the dietary intake of elements. Brown rice is hulled rice, and white rice means the rice which removed bran from brown rice by polishing. Chemical compound and elements in bran and white rice are quite different; hence, the concentration and distribution of elements in rice are also affected by the polishing rate. In the present study, the concentration and distribution of essential elements in various rice grains associated with the polishing rate were examined.International Symposium on Metallomics 200

The Concentration and Distribution of Essential Elements in Brown Rice Associated with the Polishing Rate: Use of ICP-AES and Micro-PIXE

The concentration and distribution of essential elements in brown rice grains (Oryza sativa L. var. japonica) associated with the polishing rate was determined. Rice samples were collected in Japan and polished to 5, 10, 15, and 20 % loss of the total weight of brown rice. Concentrations of 8 essential elements (P, K, Ca, Mg, Cu, Fe, Mn, and Zn) were measured by inductively coupled plasma atomic emission spectrometry (ICP-AES), and distributions of the elements in a single grain were visualized as elemental distribution maps of a cross section by micro particle induced X-ray emission (Micro-PIXE) analysis. Results of ICP-AES analysis indicated that in rice which polished from 0 to 10 % loss of weight, there were 3 patterns in the P/B ratio, which is the mean concentration of an element in polished rice divided by that of the element in the brown rice: no change (Cu and Zn), a gradual decrease (P, Mg, Mn, and Fe), and a decrease after a constant phase (Ca and K). There was no remarkable change of the P/B ratio in rice grains which polished from 10 to 20 % loss of weight. Micro-PIXE analysis images showed that P, K, Ca, Mg, Fe, and Mn were present in large amounts in the surface layer (approx. <200um thickness) of brown rice. Two sub-layers were mainly recognized in the grain surface layer in the elemental distribution maps of a cross section. The first sub-layer was approximately 130-170 um thick. The second sub-layer was approximately 20-50 um thick, and the primary part of the grain (endosperm cells and starch granules) was under it. The images showed Cu and Zn were uniformity distributed in brown rice, and their concentrations of polished rice were not affected by the polishing rate. Although ICP-AES measurements could not provide the detail structure of the surface layer of the rice grains, the trend of concentration of the elements generally agreed with the elemental distribution maps obtained Micro-PIXE analysis

UPTAKE OF 14C-ACETIC ACID BY RICE PLANT AS RELATED TO ROOT FUNCTION AND MICROBIAL ACTIVITY ON THE ROOT SURFACE

Experiments using rice plants (Oryza sativa L.) were conducted to examine uptake of 14C-acetic acid via the root and 14C behavior on the root surface. For hydroponics, three types of rice plants were cultured with 14C-acetic acid solution: complete plant, half-rooted plant, and non-rooted plant. Also, for the root incubation experiment, sterilized root and non-sterilized root were incubated with 14C-acetic acid solution. The 14C radioactivities in the plant parts and solution were measured. Non- and half-rooted plant had 14C radioactivity in their aerial part, but the complete plant did not. The trends of radioactivity levels in the solution were directly opposite to those of plant root biomass. A high level of 14C radioactivity was observed on the entire root surface of non-sterilized root in the incubation experiment, and 14C radioactivity in the solution also remarkably decreased from 7 h to 96 h after the 14C addition. These results suggest that the amount of 14C-acetic acid absorbed by the plant through the roots is very small. However, the plant absorbs 14C-acetic acid through breaks in the roots. Once 14C-acetic acid is inside the plant, it immediately transfers to the shoots. Degradation of 14C radioactivity in the solution and 14C fixation on the root surface arise from the context of microbial activities.The 12th International Conference on Environmental Remediation and Radioactive Waste Managemen

Absorption of 14C-Acetic Acid from Rice Rhizosphere

Geological disposal of radioactive waste from atomic power plants is planned to avoid radiation exposure to the public. For public health safety, it is necessary to clarify pathways on how these radioactive elements reach human beings. Absorption and assimilation of radioactive elements by food crops are important ways to understand the hazardous of radiations for human health. Carbon-14 (14C, t1/2=5.73x103 yrs) from the radioactive waste is one of the most important radioactive nuclides for environmental assessment of the waste disposals. There are several kinds of organic compounds for ordinary portland cement of radioactive waste disposals such as acetic acid, formic acid, and formaldehyde. In the present study, we examined plant uptake and assimilation of carbon through plant roots by using 14C nuclide in the form of acetic acid.Eighth Conference of the East and Southeast Asia Federation of Soil Scienc

UPTAKE OF 14C-ACETIC ACID BY RICE PLANT AS RELATED TO ROOT FUNCTION AND MICROBIAL ACTIVITY ON THE ROOT SURFACE

Experiments using rice plants (Oryza sativa L.) were conducted to examine uptake of 14C-acetic acid via the root and 14C behavior on the root surface. For hydroponics, three types of rice plants were cultured with 14C-acetic acid solution: complete plant, half-rooted plant, and non-rooted plant. Also, for the root incubation experiment, sterilized root and non-sterilized root were incubated with 14C-acetic acid solution. The 14C radioactivities in the plant parts and solution were measured. Non- and half-rooted plant had 14C radioactivity in their aerial part, but the complete plant did not. The trends of radioactivity levels in the solution were directly opposite to those of plant root biomass. A high level of 14C radioactivity was observed on the entire root surface of non-sterilized root in the incubation experiment, and 14C radioactivity in the solution also remarkably decreased from 7 h to 96 h after the 14C addition. These results suggest that the amount of 14C-acetic acid absorbed by the plant through the roots is very small. However, the plant absorbs 14C-acetic acid through breaks in the roots. Once 14C-acetic acid is inside the plant, it immediately transfers to the shoots. Degradation of 14C radioactivity in the solution and 14C fixation on the root surface arise from the context of microbial activities

Root-uptake of 14C derived from acetic acid and 14C transfer to rice edible parts

Three types of culture experiments using paddy rice (Oryza sativa L.) were performed to examine root-uptake of 14C in the form of acetic acid: double pot experiment (hydroponics), wet culture experiment (submerged sand medium), and chamber experiment (hydroponics and submerged sand medium). The 14C radioactivity in the plant, mediums, and atmospheric carbon dioxide (14CO2) in the chamber were determined, and the distribution of 14C in the plant was visualized using autoradiography. In the double pot experiment, the shoot of the plant and the lower root which was soaked in the culture solution had 14C radioactivity, but the upper root which did not have contact with the solution had none. There were also 14C radioactivity in the grains and roots in the wet culture experiment. Results of the chamber experiment showed that 14CO2 gas was released from the culture solution in both types of cultures. Results indicated that the 14C-acetic acid absorbed by rice plant through its root would be very small. Most the 14C-acetic acid was transformed into gaseous forms either in the culture solution or rhizosphere. A relatively longer time would be needed to assimilate 14C derived from acetic acid to grain parts after it was once absorbed by the shoot through the root. Availability of 14C for the plant in sand culture was considered to be decreased compared with that for the plant in the hydroponics experiment. It was suggested that rice plant absorbed and assimilated 14C through the plant roots not because of uptake of 14C-acetic acid but because of uptake of 14C in gaseous forms such as 14CO2

Behavior of 14C from acetic acid in paddy rice and root-uptake of 14C by rice plant

For safety assessment of geological disposal of transuranic (TRU) waste, it is necessary to clarify behavior of carbon such as carboxylic acids from soil to plants. Present study was conducted to examine behavior of carbon in soil-plant system using rice plant (Oryza sativa L.), three types of paddy soils, and 14C nuclide in the form of acetic acid. The plant was raised in a column (&Oslash;=20mm) filled with paddy soil. 14C-acetic acid (1, 2-14C) was injected to the column bottom (300 kBq) after grain-forming stage of the plant. Plants were harvested at 3 days, 1, 2, 3, and 4 weeks after 14C injection, and soil samples were also taken from six layers (every 5 cm each). The 14C radioactivity levels in the plant and soil layers were determined. The distribution of 14C in the plant was visualized using autoradiography. The 14C radioactivity in the soils varied significantly depending on the soil types. Although large amount of 14C in the soils would be released to air as gaseous form, 14C nuclide was still existed in the soils. In every soil, the 14C radioactivity in the surface layers was higher than that in the sub-layers. Clear images of 14C distribution in the whole plants were observed on the autoradiography at 3 weeks after 14C injection. The results indicated that inorganic 14C was produced from the breakdown of 14C-acetic acid by soil microorganisms in the early stage. Then, 14C moved upward associated with water or gas movement. In the surface layers, 14C fixation would be caused by microbial activity such as photosynthesis by algae as well as physical fixation to soil particles. Root-uptake of 14C by the plant was carried out as uptake of 14C in inorganic forms such as CO2.７ｔｈ International Symposium for Subsurface Microbiolog

Root-uptake of 14C derived from acetic acid by root vegetables

Sand culture using radish (Raphanus sativus L.) and hydroponics using carrot (Daucus carota L.) were conducted to examine root-uptake of carbon and its assimilation in the form of 14C-acetic acid. 14C-acetic acid (1, 2-14C, radioactivity: 74 kBq) was added to each pot. Radishes were grown under the dark conditions or the light conditions for 24 h. Carrot were grown under the light conditions after 14C-acetic acid addition (radioactivity: 19 kBq). The 14C radioactivity in each plant part was determined. The distribution of 14C in the plants was visualized using autoradiography. For a comparison, autoradiography was also done using 22Na. The results indicated that the root vegetables absorbed 14C through the roots and assimilated it into the shoots and edible parts. However, the amount of 14C-acetic acid absorbed by plants through the roots was considered to be very small. Absorption and assimilation of 14C seemed to be carried out not because of uptake of 14C-acetic acid but because of uptake of 14C in inorganic forms with very low concentration. 14C dominantly transferred to the plant parts where were physiologically active. 14C movement in the plant did not have a close relation to water movement unlike 22Na movement

Root-uptake of C-14 acetic acid by various plants and C-14 dynamics surrounding the experimental tessera

Carbon-14 (C-14, t1/2=5.73*103 yrs) from radioactive waste is one of the most important radioactive nuclides for environmental assessment in the context of geological disposal, and understanding the transfer of radioactive elements to plants is essential for public health safety. In order to obtain fundamental knowledge, culture experiments using marigold (Tagetes patula L.), tall fescue (Festuca arundinacea S.), paddy rice (Oryza sativa L.), radish (Raphanus sativus L.), and carrot (Daucus carota L.) plants were conducted to examine root-uptake and dynamics of C-14 in the laboratory. The C-14 radioactivity in each plant part (e.g. shoot, root, edible part, etc.), medium (e.g. culture solution, sand, etc.), and air was determined. The distribution of C-14 in the plants was visualized using autoradiography. For a comparison, autoradiography was also done using Na-22. Results of the present study indicated that C-14 labeled CO2 gas was released from the culture solution to the atmosphere. Clear autoradiography images were observed in plants for the shoots and lower roots which were soaked in the culture solution. The upper roots which were not soaked in the culture solution were not clearly imaged. In the radiotracer experiment using Na-22, a clear image was observed for the whole carrot seedling, even including the upper root, on the autoradiography. However, the amounts of C-14 acetic acid absorbed by all the plants through their roots were considered to be very small. Inorganic carbon transformed from C-14 acetic acid would be taken up by plants through the roots, and some fraction of C-14 would be assimilated into the shoots by photosynthesis