Many metals are essential for plants and humans. Knowledge of metal distribution in plant tissues in vivo contributes to the understanding of physiological mechanisms of metal uptake, accumulation and sequestration. For those studies, X-rays are a non-destructive tool, especially suited to study metals in plants. We present microfluorescence imaging of trace elements in living plants using a customized benchtop X-ray fluorescence machine. The system was optimized by additional detector shielding to minimize stray counts, and by a custom-made measuring chamber to ensure sample integrity. Protocols of data recording and analysis were optimised to minimise artefacts. We show that Zn distribution maps of whole leaves in high resolution are easily attainable in the hyperaccumulator Noccaea caerulescens. The sensitivity of the method was further shown by analysis of micro- (Cu, Ni, Fe, Zn) and macronutrients (Ca, K) in non-hyperaccumulating crop plants (soybean roots and pepper leaves), which could be obtained in high resolution for scan areas of several millimetres. This allows to study trace metal distribution in shoots and roots with a wide overview of the object, and thus avoids making conclusions based on singular features of tiny spots. The custom-made measuring chamber with continuous humidity and air supply coupled to devices for imaging chlorophyll fluorescence kinetic measurements enabled direct correlation of element distribution with photosynthesis. Leaf samples remained vital even after 20 h of X-ray measurements. Subtle changes in some of photosynthetic parameters in response to the X-ray radiation are discussed. We show that using an optimized benchtop machine, with protocols for measurement and quantification tailored for plant analyses, trace metal distribution can be investigated in a reliable manner in intact, living plant leaves and roots. Zinc distribution maps showed higher accumulation in the tips and the veins of young leaves compared to the mesophyll tissue, while in the older leaves the distribution was more homogeneous.

中文翻译：

---

利用基于实验室的显微 X 射线荧光成像分析植物中的痕量金属分布。

许多金属对植物和人类都是必不可少的。了解体内植物组织中的金属分布有助于理解金属吸收、积累和螯合的生理机制。对于这些研究，X 射线是一种非破坏性工具，特别适合研究植物中的金属。我们使用定制的台式 X 射线荧光机对活植物中的微量元素进行微荧光成像。该系统通过额外的检测器屏蔽来优化杂散计数，并通过定制的测量室来确保样品的完整性。数据记录和分析协议进行了优化，以尽量减少伪影。我们表明，在超富集 Noccaea caerulescens 中很容易获得高分辨率的全叶 Zn 分布图。通过对非高积累作物（大豆根和辣椒叶）中微量元素（Cu、Ni、Fe、Zn）和常量营养素（Ca、K）的分析进一步显示了该方法的灵敏度，这些元素可以高分辨率获得适用于几毫米的扫描区域。这允许研究芽和根中的微量金属分布，并对对象进行广泛的了解，从而避免基于微小斑点的单一特征做出结论。具有连续湿度和空气供应的定制测量室与叶绿素荧光动力学测量成像设备相结合，使元素分布与光合作用直接相关。即使经过 20 小时的 X 射线测量，叶子样本仍然很重要。讨论了响应 X 射线辐射的一些光合参数的细微变化。我们表明，使用优化的台式机器，以及为植物分析量身定制的测量和量化协议，可以在完整的活植物叶子和根中以可靠的方式研究痕量金属分布。锌分布图显示，与叶肉组织相比，幼叶的尖端和叶脉中的积累量更高，而在老叶中分布更均匀。