Screening of Wintering Plants for Remediation of Cd-Contaminated Paddy Soil.

On heavy metals (HMs) contaminated paddy soil, non-agricultural period is chance for reducing of HMs. So, application of wintering plant could adapt for paddy field contaminated by HMs under low-temperature condition (>3°C) is needed. Experiment for screening of wintering plants divided into 3-steps. First, we investigated anti-oxidative mechanism against cadmium (Cd) stress under the low-temperature for plants (Astragalus sinicus, Vicia villosa, Secale cereale). There were exposed to two temperature conditions (2.5, 15°C) and two Cd concentrations (0, 50 μM). Cd accumulation and anti-oxidative enzyme (Superoxide dismutase; SOD, Catalase; CAT) activities were analyzed. Cd accumulation in Vicia villosa was the highest on all temperature. SOD and CAT activities were higher at 2.5°C temperature and 50 μM Cd in Vicia villosa and Secale cereale. As second experiment, plants were sowed with different seedling densities (2, 5, 10 g m^-2) on field to evaluate growth rate of plants and Cd uptake. Secale cereale showed higher biomass and Cd contents. From these result, Secale cereale were selected for remediation of paddy soil. Next, Pot scale experiment was designed to verify effects temperature on available fraction of HMs. Plant growth rate and Cd concentration were measured. Cd concentration of soil solution around root measured. Available HMs extracted with water (deionized water) and DTPA-TEA compared to HMs in soil solution. Plants in fertilized pot were produced the highest biomass yield on same temperature condition. Cd concentration and contents were highest in fertilized pot on normal temperature pot. Cd concentration in soil solution decreased regardless of fertilizing and temperature. Available Cd concentration, extracted with water and DTPA-TEA, showed lowest concentration in fertilized pot on normal temperature. These results suggest that introducing of wintering plant could be useful to reducing available HMs in contaminated paddy soil on appropriate temperature condition, and planting strategies were needed for successful application.