The Department of Botany, La Trobe University, Melbourne, VIC, 3086, Australia.
Planta. 2012 Nov;236(5):1459-70. doi: 10.1007/s00425-012-1699-6. Epub 2012 Jul 7.
Plant manganese (Mn) hyperaccumulation provides unusual insight into homeostasis of this essential micronutrient, in particular its excessive storage in shoot tissues. The compartmentation of hyperaccumulated foliar Mn appears exceptional among metal hyperaccumulators, since it occurs via specific microdistribution patterns. Here, three associated Mn hyperaccumulators, Virotia neurophylla, Maytenus fournieri, and Garcinia amplexicaulis exhibiting distinctly different Mn detoxification strategies were examined. Non-invasive sample preparation in conjunction with cryo scanning electron microscopy (SEM) was used to obtain in vivo quantitative microprobe X-ray and anatomical data from fully hydrated cells. Highly vacuolated large palisade mesophyll cells in V. neurophylla leaves were found to contain around 650 mM Mn. The large non-photosynthetic hypodermal cells of M. fournieri leaves, also with high vacuolar content, and the main site for Mn disposal, had an estimated mean vacuolar Mn concentration of around 600 mM. Previous qualitative X-ray mapping had shown Mn to be almost evenly sequestered across the entire leaf cross section of G. amplexicaulis. However, quantitative data obtained here showed a marked variation in localised concentrations that ranged between ~15 and >800 mM. Notable among these were mean values of >600 mM in spongy mesophyll cells, and ~800 mM within cells of a narrow sub epidermal layer preceding the palisade mesophyll. This study demonstrated the extraordinary Mn carrying capacities of different types of leaf cell vacuoles.
植物锰（Mn）超积累为研究这种必需微量元素的体内平衡提供了独特的视角，尤其是其在 shoot 组织中的过度储存。在金属超积累植物中，超积累叶部 Mn 的区室化似乎是特殊的，因为它是通过特定的微观分布模式发生的。在这里，研究了三种相关的 Mn 超积累植物，即 Virotia neurophylla、Maytenus fournieri 和 Garcinia amplexicaulis，它们表现出截然不同的 Mn 解毒策略。使用非侵入性样品制备方法结合 cryo 扫描电子显微镜（SEM），从完全水合的细胞中获得体内定量微探针 X 射线和解剖学数据。在 V. neurophylla 叶片的大栅栏状叶肉细胞中发现了高度液泡化的细胞，其中含有约 650 mM 的 Mn。M. fournieri 叶片中的大型非光合下皮细胞也具有高液泡含量，并且是 Mn 处置的主要部位，估计其平均液泡 Mn 浓度约为 600 mM。先前的定性 X 射线映射表明 Mn 几乎均匀地分布在 G. amplexicaulis 叶片的整个横截面中。然而，这里获得的定量数据显示局部浓度存在明显变化，范围在15 至>800 mM 之间。其中值得注意的是，海绵状叶肉细胞中的平均值>600 mM，以及在紧邻栅栏状叶肉细胞之前的狭窄下皮层细胞中的800 mM。这项研究表明了不同类型叶片细胞液泡的非凡 Mn 承载能力。
