Sweetpotato (Ipomoea batatas L.) possess great application prospects due to their low cadmium (Cd) concentration within their storage roots despite growth on Cd-polluted fields. The mechanisms of low Cd accumulation in storage root is not entirely clear. We found that the blocking effect of Cd uptake in the root absorption system and the characteristics of Cd distribution in storage root play a decisive role in the regulation of low Cd accumulation in storage root. Cd absorbed from the rhizosphere mainly accumulated in feeder roots in Cd dose-dependent accumulation analyses. Meanwhile, we found that Cd absorbed by the peels of storage root was mainly transported from peels to shoots, rather than directly into the fleshed storage root. Further analysis indicated that Cd uptake, transport, and distribution in sweetpotato hinges on whether Cd enters the plant plasma membrane by either the symplast or apoplast pathway. The Cd concentration in feeder root decreased after respiratory inhibitors CCCP and DNP treatment and increased after the culture temperature was raised from 28 ℃ to 35 ℃. Non-invasive microelectrode Cd flux measurements further revealed that Cd uptake in feeder root was affected greatly by the Cd concentration of the solution and was markedly reduced by respiratory inhibitor CCCP. Relative to the elongation zone and mature zone, the meristematic zone was the main site of Cd uptake in the root absorption system. This study suggests that inhibition of Cd uptake by the root absorption system and the characteristics of Cd distribution in storage root are the main reasons for low cadmium accumulation in storage root.

中文翻译：

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甘薯贮藏根中低镉积累机制

甘薯 (Ipomoea batatas L.) 尽管生长在受镉污染的土地上，但其贮藏根中的镉 (Cd) 浓度较低，因此具有很大的应用前景。贮藏根中低镉积累的机制尚不完全清楚。我们发现根系吸收系统中Cd吸收的阻断作用和贮藏根中Cd的分布特征对贮藏根中低Cd积累的调控具有决定性作用。在镉剂量依赖性积累分析中，从根际吸收的镉主要在饲养根中积累。同时，我们发现贮藏根果皮吸收的Cd主要是从果皮输送到地上部，而不是直接进入多肉贮藏根。进一步分析表明，Cd 的吸收、运输、甘薯中的分布取决于 Cd 是否通过共质体或质外体途径进入植物质膜。呼吸抑制剂CCCP和DNP处理后饲养根中Cd浓度降低，培养温度从28℃升高到35℃后升高。非侵入性微电极 Cd 通量测量进一步表明，饲养根中 Cd 的吸收受溶液中 Cd 浓度的影响很大，呼吸抑制剂 CCCP 显着降低。相对于伸长区和成熟区，分生区是根系吸收系统中镉吸收的主要部位。本研究表明，根系吸收系统对Cd吸收的抑制以及贮藏根中Cd分布的特点是贮藏根中镉积累量低的主要原因。