施硒对不同镉污染土壤当季及后茬水稻镉吸收转运的影响

Effects of selenium fertilization on cadmium uptake and transport in rice crop in different cadmiumcontaminated soils during two consecutive seasons

为探讨施硒对当季和后茬水稻镉吸收转运的影响,本研究选取基本性质相似的中、重度镉污染稻田土壤为对象,采取盆栽试验的方法,研究不同施硒量(0.5、1.0、2.0、4.0 mg·kg^(-1))对当季及后茬水稻各部位镉与硒含量的影响,并探讨其作用机理。结果表明:中度镉污染稻田土壤仅施硒2.0 mg∙kg^(-1)处理使当季稻米镉含量降低28.6%(P<0.05);施硒对重度镉污染土壤当季稻米镉含量均有降低作用,其中施硒1.0 mg∙kg^(-1)处理的降镉效果显著,镉含量降低36.1%(P<0.05);施硒处理使两种土壤后茬稻米镉含量显著降低30.9%~50.7%(P<0.05)。适量施硒(1.0、2.0 mg∙kg^(-1))使当季水稻镉TF茎/根降低21.5%~28.3%(P<0.05),而对后茬水稻镉转运则无显著影响。中、重度镉污染土壤施硒,可增加当季和后茬水稻植株各部位硒含量,硒含量增幅随施硒量增加而增加。稻米镉富集系数随稻米硒含量增加呈自然对数降低(P<0.05)。中度镉污染土壤施硒0.5 mg∙kg^(-1)、重度镉污染土壤施硒≤1.0 mg∙kg^(-1)时,当季和后茬稻米硒含量均低于1.0 mg∙kg^(-1)。研究表明,施硒可通过降低水稻镉吸收而有效降低后茬稻米镉含量,但适宜的施硒量仍需田间验证确定。

A pot experiment,with four rates of selenium(Se)concentration(0.5,1.0,2.0 mg∙kg^(-1) and 4.0 mg∙kg^(-1)),was conducted to investigate the effects of Se fertilization on the absorption and transport mechanisms of cadmium(Cd)in rice during two consecutive seasons under moderately and severely Cd contaminated soils.The Cd and Se contents in rice plant tissues were determined.The results showed that the Cd content of the current season rice grain decreased by 28.6%only when Se dose was 2.0 mg∙kg^(-1) under moderately Cd contaminated paddy soil.However,the Cd content of rice under severely Cd polluted soil decreased by 36.1%only when the dose of Se was 1.0 mg∙kg^(-1).The Cd content of rice grains of the subsequent season significantly decreased by 30.9%-50.7%in each Se treatment.Application of 1.0 mg∙kg^(-1) and 2.0 mg∙kg^(-1) Se in the current season rice significantly reduced the transfer coefficient of Cd from roots to shoots by 21.5%-28.3%,with no significant effect on Cd transport in the rice crop during the subsequent season.The Se content in all parts of rice plants under moderately and severely Cd contaminated soils during the current and subsequent seasons increased with Se application rate.With the increase of Se content,the Cd enrichment coefficient of rice grain significantly decreased when the natural logarithm was used.When the Se dose was 0.5 mg∙kg^(-1) in moderately Cd contaminated soil and≤1.0 mg∙kg^(-1) in severely Cd contaminated soil,the Se content in rice of the current and the subsequent seasons was less than 1.0 mg∙kg^(-1).Therefore,Se application can effectively reduce the Cd content in subsequent rice by reducing Cd uptake by the rice crop,but the appropriate Se application level still needs to be confirmed under field conditions.