Background and aims

This study aimed to gain insight into the biochemical mechanisms of Ni movement in Odontarrhena inflata and Aurinia saxatilis.

Methods

We examined the effects of Ni exposure on the concentrations of histidine and nicotianamine in roots, shoots, and in xylem sap of Odontarrhena inflata (as a Ni hyperaccumulator) and Aurinia saxatilis as a non-accumulator. Furthermore, we analysed the effects of Fe and Zn deficiency, and of an apoplastic pathway blocker, on the mobility of Ni.

Results

In plants unexposed to Ni, root His and shoot NA concentrations were higher in O. inflata than in A. saxatilis. Ni exposure caused an increase in His in the xylem sap of O. inflata. Ni exposure caused concentration-dependent increases in shoot His and in root NA concentrations, which were similar in both species for His and distinct between the two species for NA. Fe deficiency, followed by a short-term Fe luxury and Ni exposure, led to enhanced Ni uptake and Ni flux from the root to the shoot of O. inflata. By contrast, we observed decreased Ni loading into the xylem in O. inflata subjected to Zn deficiency. An apoplastic pathway blocker resulted in a decrease in root Ni levels by almost 20%, and in decreased shoot Ni concentrations only under high Ni exposure.

Conclusion

The processes enhanced in response to Fe deficiency can contribute to root uptake and xylem loading of Ni in the hyperaccumulator species. The contribution of the apoplastic pathway to root-to-shoot Ni flux is negligible under natural ecological conditions.

中文翻译：

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高蓄积器Odontarrhena inflata和非蓄积器Aurinia saxatilis中木质部镍负载的比较生理学

 背景和目标

本研究旨在深入了解 Odontarrhena inflata 和 Aurinia saxatis 中 Ni 运动的生化机制。

 方法

我们研究了 Ni 暴露对 Odontarrhena inflata （作为 Ni 超积累剂） 和 Aurinia saxatilis 作为非积累剂的根、芽和木质部汁液中组氨酸和烟酰胺浓度的影响。此外，我们分析了 Fe 和 Zn 缺乏以及质外体途径阻滞剂对 Ni 迁移率的影响。

 结果

在未暴露于 Ni 的植物中，O. inflata 的根 His 和芽 NA 浓度高于 A. saxatilis。Ni 暴露导致 O. inflata 木质部汁液中 His 的增加。Ni 暴露导致地上部 His 和根 NA 浓度呈浓度依赖性增加，这在两个物种的 His 中相似，而在两个物种中 NA 则不同。Fe 缺乏，随后是短期的 Fe luxury 和 Ni 暴露，导致 Ni 吸收和 Ni 通量从 O. inflata 的根部到芽的 Ni 通量增强。相比之下，我们观察到在 O. inflata 中，在 Zn 缺乏的情况下，进入木质部的 Ni 负载减少 质外体途径阻滞剂导致根 Ni 水平降低近 20%，并且仅在高 Ni 暴露下地上部 Ni 浓度降低。

 结论

响应 Fe 缺乏而增强的过程有助于 hyperaccumulator 物种中 Ni 的根吸收和木质部负载。在自然生态条件下，质外体途径对根-芽 Ni 通量的贡献可以忽略不计。