缺Fe预处理对Fe、Cd根际吸附与水稻吸收和转运的影响

Adsorption of Iron and Cadmium in Rhizosphere and Their Uptake and Translocation in Rice Pretreated with Iron Deficiency

采用蛭石-营养液联合培养试验,测定并比较了缺Fe预处理和正常Fe营养供应下水稻根际pH值、Eh、根际蛭石和根表吸附的Fe、Cd数量,及根系分泌的低分子量有机酸(LMWOAs)种类与数量,探讨了缺Fe预处理下的根际性状和LMWOAs对根际Fe、Cd吸附与水稻吸收转运的影响。结果表明,缺Fe预处理后水稻根际酸度增加,根际还原性增强,稻根分泌的低分子量有机酸降低;根际蛭石表面吸附的Fe变化不大,而稻根表面吸附沉积的Fe减少,根际蛭石非结晶态Cd含量增加,根表Fe膜中的Cd含量升高但不显著,水稻根系Cd含量和积累量上升,说明缺Fe减少了两种元素在根际和根表吸附位点的竞争,但由于Fe膜对Cd的阻挡作用有限,促进了水稻对Cd的吸收。不过,缺Fe导致水稻根部向地上部转运的Cd、Fe下降,可能与根内低分子量有机酸载体数量的下降有关。

Cadmium(Cd) accumulation in rice poses a serious risk to human health.Cadmium bioavailability may be affected by the chemistry of iron(Fe)in rice rhizosphere.Here we investigated the effects of rhizospheric conditions and low molecular weight organic acids(LMWOAs)secreted from rice roots with iron deficiency pretreatment on Cd and Fe adsorption on the vermiculite/root surface and their uptake and translocation by rice using nutrient solution-vermiculite culture.Pretreatment with Fe deficiency increased acidity and reducing condition in the rhizosphere,but decreased amount of LMWOAs.Iron deficiency had little influence on Fe adsorption on the surface of vermiculite,but decreased that on the rice root.Compared with normal Fe,Fe deficiency caused increases in non-crystalline Cd on the vermiculite,whereas had no impact on Cd in the Fe film.Enhanced concentration and accumulation of Cd in rice root suggested that Fe deficiency resulted in less competition of these two elements in the rhizosphere and on the roots.Iron plaque on rice roots showed limited shielding effect on Cd uptake by rice,leading to increased Cd absorption by rice.However,Fe deficiency decreased the Cd and Fe translocation from roots to shoots,maybe due to declined LMWOA carriers in rice roots.