Cadmium uptake dynamics and translocation in rice seedling: Influence of different forms of selenium

• Exogenous Se slightly increased Cd uptake by rice seedlings at the initial Cd exposure.
• Exogenous Se decreased Cd uptake and transportation when exposed to Cd longer.
• Endogenous Se decreased Cd uptake and translocation from rice roots to shoots.
• Selenite was more effective than selenate in decreasing Cd uptake and translocation.

Selenium (Se) can alleviate the toxicity of cadmium (Cd), but little is known about its mechanism in Cd uptake and translocation in plants. We investigated the effects of exogenous selenite, selenate, and selenomethionine (SeMet) on Cd uptake and translocation within rice (Oryza sativa L., Zhunliangyou 608) seedlings, and the concentration-dependent uptake kinetics of Cd into rice roots (with or without Se) were determined. The effect of the endogenous Se pool on Cd uptake was also investigated. Results of uptake kinetics showed that selenite slightly promoted Cd influx during 1 h of exposure, compared with no selenite addition; Vmax of Cd uptake increased by 13.8% in 10 μM selenite treatment; while the presence of selenate had no effect on the influx of Cd. When exposed to Cd (5 μM) over 20 h (with selenite) or 30 h (with selenate or SeMet), Se addition (5 μM) decreased Cd uptake and root-to-shoot translocation; after 30 h selenite, selenate, or SeMet addition decreased Cd uptake by roots by 28.6%, 17.7% or 12.1%, respectively. Besides, as the selenite levels in the treatment solutions (1 μM Cd) increased (0, 0.1, 1, and 5 μM, Se), Cd uptake and translocation were both significantly reduced, while the inhibitive effect was more significant at lower levels of selenate. Pretreatment of selenite or selenate (5 μM) also decreased Cd uptake by 24.9% or 15.7%, and reduced the root-to-shoot transfer factor by 41.4% or 36.2% after 144 h of subjection to Cd (5 μM), respectively. The presence of selenite decreased Cd content more effectively than did selenate. Our results demonstrated that Se can effectively reduce the Cd translocation from roots to shoots in rice seedlings.

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