Dou Changming, Qi Cuicui
Anhui Provincial Academy of Eco-Environmental Science Research, Hefei 230061, China.
Toxics. 2023 Dec 1;11(12):977. doi: 10.3390/toxics11120977.
Manganese (Mn) exclusion in the Mn hyperaccumulator pokeweed ( L.) was investigated. Hydroponic experiments were carried out to observe the responses of pokeweeds continually exposed to high levels of Mn. In this study, crystals were observed to appear firstly on the root hair, and soon after, more crystals appeared on the root surface, and crystals of Mn phosphate were observed to appear on the root surface in a time sequence negatively correlated with the number of leaves treated with 5 mM Mn. Crystals were identified via phase analysis of X-ray diffraction and element analysis, and these white insoluble crystals were identified using XRD to be Mn phosphate, with the molecular formula (Mn,Fe)(PO)·4HO. The nutrient solution pH increased from 4.5 to about 5.6 before the crystals appeared. Mn phosphate crystals appeared in all solutions except those without phosphate and emerged earlier in the solutions containing no Fe. Compared with control group, pokeweed accumulated much more Mn in the leaves when treated without phosphate or Fe. The present study suggests that pokeweed can exclude Mn by means of rhizosphere precipitation by phosphate to form Mn phosphate crystals that accumulate on the root surface. Although the detailed mechanism requires further investigation, this study provides the first direct evidence of a novel strategy to inhibit Mn uptake in the roots of a hyperaccumulator in a P-enriched environment.
对锰超积累植物商陆（Phytolacca americana L.）中的锰（Mn）排斥现象进行了研究。开展了水培实验，以观察持续暴露于高浓度锰环境下的商陆的反应。在本研究中，首先观察到晶体出现在根毛上，随后不久，根表面出现了更多晶体，并且观察到磷酸锰晶体按时间顺序出现在根表面，其出现时间与用5 mM锰处理的叶片数量呈负相关。通过X射线衍射的相分析和元素分析对晶体进行了鉴定，利用X射线衍射确定这些白色不溶性晶体为磷酸锰，分子式为（Mn,Fe）（PO₄）·4H₂O。在晶体出现之前，营养液的pH值从4.5升高到了约5.6。除不含磷酸盐的溶液外，所有溶液中均出现了磷酸锰晶体，且在不含铁的溶液中出现得更早。与对照组相比，在无磷酸盐或铁处理时，商陆叶片中积累的锰要多得多。本研究表明，商陆可通过根际磷酸盐沉淀形成磷酸锰晶体的方式来排斥锰，这些晶体积累在根表面。尽管详细机制有待进一步研究，但本研究首次提供了在富磷环境中一种超积累植物根系抑制锰吸收新策略的直接证据。
