In order to investigate the genotypic variations of Zn accumulation in rice plant, thirty-five rice cultivars of different cultivar groups (temperate japonica, tropical japonica, tongil, and indica) were irrigated with irrigation water containing 2 ppm Zn throughout all growth season in a field experiments in 2007. At harvest, thirty-five rice cultivars showed large difference in Zn concentrations in root, shoot, straw, grain, chaff, brown rice, rice bran, and polished rice. Zn concentrations in polished rice ranged from 5.15 to 21.24 mg/kg. The total Zn accumulation in shoot varied from 12.18 to 54.84 mg/m2. Two japonica rice cultivar groups (temperate japonica, and tropical japonica) presented the higher Zn concentration in shoot compared to indica and Tongil cultivar groups. The large genotypic variation suggested the possibility of breeding low Zn accumulating rice varieties.

In the present experiment, thirty-five rice cultivars were irrigated by irrigation water containing 2 ppm Ni throughout all growth season in order to investigate the genotypic differences in Ni accumulation of rice. At harvest, thirty-five rice cultivars showed large difference in Ni concentrations in shoot, straw, grain, chaff, brown rice, rice bran, and polished rice, but not in root. Ni concentraions in polished rice ranged from 0.43 to 2.28 mg/kg. The total Ni accumulation of shoot varied from 0.63 to 2.93 mg/m2. Indica cultivar groups presented the highest Ni concentration of polished rice, but no significant difference from the other cultivar group. At the same time, indica cultivar group significantly accumulated more Ni by shoot compared to the other cultivar groups. The large genotypic variation suggested the possibility to breed low Ni accumulating rice cultivar.

In order to investigate the genotypic differences in Pb accumulation of rice, thirty-five rice cultivars were irrigated by irrigation water containing 10 ppm Pb throughout all growth season under field condition. At harvest, thirty-five rice cultivars showed significant difference in Pb concentrations in straw, grain, chaff, brown rice, rice bran, and polished rice, but not in root. Pb concentration in polished rice ranged from 0.02 to 0.22 mg/kg. The total Pb accumulation in shoot varied from 0.77 to 2.74 mg/m2. There were no significant difference of Pb concentration in all of rice parts among four rice cultivar groups. Indica and tongil cultivar groups presented the higher Pb accumulation in shoot. The large genotypic variation suggested the possibility of breeding low Pb accumulating rice cultivar.

In order to investigate the genotypic differences in Cu accumulation of rice, 35 rice cultivars of different cultivar groups (temperate japonica, tropical japonica, tongil, and indica) were cultivated in a field condition that rice was irrigated by irrigation water containing 2 ppm Cu throughout all growing season in 2007. Thirty-five rice cultivars showed large differences in Cu concentrations in all rice parts, including root, shoot, straw, grain, chaff, brown rice, rice bran, and polished rice. Cu concentrations in polished rice ranged from 0.78 to 2.84 mg/kg. The total Cu accumulation of shoot varied from 1.31 to 4.54 mg/m2. Indica and tongil cultivar groups presented the higher Cu concentration and accumulation comparing the two japonica rice cultivar groups (temperate japonica and tropical japonica). The large genotypic variation suggested the possibility of breeding low Cu accumulating rice cultivar.

Cd contamination in irrigation water can imperil human health through food chain. In order to investigate the genotypic differences in Cd accumulation of rice, thirty-five rice cultivars of different cultivar groups (temperate japonica, tropical japonica, tongil, and indica) were grown with irrigation water containing 2 ppm Cd throughout all growing season under the field condition in 2007. At harvest, highly significant differences in Cd concentration in different rice parts (root, shoot, straw, grain, chaff, brown rice, rice bran, and polished rice) was found among rice varieties and rice cultivar groups. Cd concentration of polished rice ranged from 0.26 to 1.85 mg/kg. The total Cd accumulation of shoot varied from 0.69 to 7.87 mg/m2. Indica cultivar group showed significantly higher Cd concentration and accumulation compared to the other rice cultivar groups. On the other hand, the distribution ratio in polished rice was the highest in Tongil cultivar group. The large genotypic variation suggested the possibility of breeding low Cd accumulating rice variety.

Leaf color can be used as an indicator of the plant healthiness, and thus digital image analysis may provide farmers and researchers with time- and resource-saving methods for diagnosing plant nutrient status. The digital images are dependent on the ambient light, therefore the color indices of digital images should be compensated for the difference of ambient light. The objectives of this study were to develope the calibration methods for color indices under variable irradiance condition. Four color panels were used for RGB (Red, Green, Blue) values and color indices calibration purpose. Reflectance for each panel was measured by spectro-radiometer with a waveband range of 300 - 1100 nm. The reflectance values of four color panels was used as a reference for calibration of RGB values and color indices. Using digital camera color images were taken for rice canopies together with reference panel that was set up at the level of canopy surface. Digital images were obtained form rice fields with variable nitrogen fertilization managements at active tillering to panicle initiation stage. The calibration coefficients for color image indices were calculated by using the linear regression equation between the pixel values of color image for reference panel and their known reflectance values. The determination coefficients (r2) of linear regression between non-calibrated mean B values of plant pixels in color image and shoot nitrogen contents in four rice varieties, Odae, Hwasung, Chucheong, and Ilpum, was 0.30, 0.27, 0.37, and 0.27, respectively, while the respective r2 values were increased to 0.79, 0.85, 0.77, and 0.53.by applying the calibration coefficient. These results imply that color digital image analysis could be a promising method for diagnosing nitrogen nutrition status of rice canopy.