Effects of Se on Cd content and distribution in rice plant under Cd stress in cold climate

【Objectives】 Effects of Se application on Cd accumulation and distribution in rice organs and content of Cd in rice grain were studied to explore countermeasures for rice planting in Cd polluted soils.【Methods】 A pot experimentwas conducted using rice cultivar Kenjiandao 6 as experimental material.Four levels of Cd additions (0, 2, 4 and 8 mg/kg soil) and 3 Se levels (0, 0.07 and 0.14 mg/kg soil) for each Cd addition were designed. The rice plants were harvested at the maturity stage, the Cd contents in leaves, stems, sheaths, roots, brown rice and polished rice were determined, Cd accumulation amounts and distribution ratios in rice organs were calculated, and the Se contents in brown rice and polished rice, and dry matter weight were determined as well. 【Results】1) When the added Cd concentration in soil is increased from 0 to 4 mg/kg, the Cd contents in different organs of rice, brown rice and polished rice are increased significantly. When added Cd concentration is higher than 4 mg/kg, the increases of the Cd contents in brown rice and polished rice are not significant. The Cd contents in brown rice are 0.221 mg/kg and 0.234 mg/kg under the Cd2 (4 mg/kg) and Cd3 (8 mg/kg) treatments without Se application which are 15.8 and 16.7 times higher than that of Cd0, higher than the national food safety standards of China for Cd content (0.2 mg/kg). The Cd content in polished rice is 0.174 mg/kg, which conforms to the national food safety standards of China. 2) The Cd contents and Cd accumulation amounts in different organs of rice and brown rice, polished rice are decreased significantly with the increase of Se concentration under the same Cd concentration, and larger declines of the Cd content are observed under the Se2 (0.14 mg/kg) treatment. Under Cd1 (2 mg/kg), the Cd content in polished rice in the Se2 treatment is reduced by 31.5% (P＜0.01) compared to Se0.3) Sequence of the Cd distribution in rice organs is roots stems and sheaths grains leaves. The Cd distribution portion in roots is enhanced with the increase of Se concentration as Cd distribution in other organs is declined at the same time. The Cd distribution portion in rice husk is increased with the increase of Se concentration, meanwhile, the Cd distribution portion in polished rice is decreased. Under Cd1, the Cd distribution portions in roots and grains are in the range of 60.9%-67.8% and 12.6-13.8%, the Cd distribution portion in rice husk with Se2 is 5.2 percentage points higher than that of Se0, while the Cd distribution portion in polished rice with same treatment is lower than Se0 by 6.2 percentage points. 4) The dry matter weights of different organs are increased significantly with the increase of Se concentration under same Cd concentration. Under the concentrations of Cd1, Cd2 and Cd3, the dry matter weights of grain with the Se2 treatment are increased by 6.5% (P＜0.01), 5.2% (P＜0.05) and 11.3% (P＜0.01), respectively compared to Se0. 【Conclusions】 Se application could reduce Cd concentration in rice plants, brown rice and polished rice, and reduce Cd transportation into polished rice. Se application shows the most significant effects when the added soil Cd concentration is 2 mg/kg,and the 0.07 mg/kg of Se application treatment exhibits the best effects.