From cell to cell, tissue to tissue: Pathways in low-temperature wood silicification

硅化是植物细胞保存中最重要的硅化过程，它可以使细胞保存得非常细致。近世纪来，人们对理解这一过程一直很感兴趣，现在已知任何能够将升高的二氧化硅带入溶液的基质都能够使植物材料硅化。富含二氧化硅的溶液进入木材，并通过在细胞壁上形成一层膜来保护细胞。目前，分析技术通常用于表征木材硅化的地球化学。然而，几乎所有的研究都只关注细胞中矿化已经开始或完成后的木材硅化。实际上，在二氧化硅沉淀在木材细胞中之前，含水二氧化硅进入树木的细胞和组织途径几乎是未知的。在这里，我们提出了一个有凝聚力的分析和实验研究计划，旨在阐明含水二氧化硅进入木材和其他木质组织，如种子球果的组织和细胞途径的四项研究。第一项研究将确定在四个直立针叶树树苗植根于一个在黄石国家公园，怀俄明州，美国温泉的烧结裙的二氧化硅负载水的路径。第二项研究将确定莱斯沃斯泥炭森林中1700万年古树渗出的滴水结构是否代表树木还活着时富含二氧化硅的树液，这意味着树木参与了细胞的自我矿化。第三项研究将追踪二氧化硅从沉积物基质进入异地原木、化石木和球果的途径。第四项研究将包括一系列实验室实验，追踪含水二氧化硅在木材组织中从一个细胞到另一个细胞的途径。使用水，火山玻璃粉，和热源，初期硅化将产生在各种密度的针叶树和被子植物木材，有和没有树皮。横向是木材组织相对于含水二氧化硅流的取向。此外，还将通过在有树皮的树枝中诱导硅化来研究树皮是否会阻碍二氧化硅的进入，并将尖端技术应用于二氧化硅、其他矿物质和残留木质素在微米和纳米级水平上的分布的成像、绘图和分析。这些主要涉及非侵入性、非破坏性的表面分析方法，例如包括波色散X射线分析（WDX）、共焦拉曼光谱（CHRS）、X射线衍射（XRD）、氦离子显微镜（HIM）、X射线光电子能谱（XPS）、飞行时间质谱（ToF-SIMS）和基质辅助激光解吸/电离飞行时间质谱（MALDI-ToF）。高分辨率的研究也将使用扫描电子显微镜，背散射背散射电子显微镜和透射电子显微镜进行。

Silicification is the most important fossilization process for cellular preservation in plants, which can result in cells preserved in exquisite detail. Understanding this process has been of great interest for nearly a century, and it is now known that any substrate that is able to bring elevated silica into solution is capable of silicifying plant material. The silica-rich solution enters wood and initially preserves cells by templating a film on the cell walls. Currently, analytical techniques are routinely used to characterize the geochemistry involved in wood silicification. However, nearly all studies are concerned with wood silicification only after mineralization in the cells has already begun or been completed. Indeed, what is virtually unknown is the cellular and tissue pathway of aqueous silica into the tree before silica is precipitated in the wood cells. Here we present a cohesive analytical and experimental research program of four studies aimed at elucidating the tissue and cellular pathway of aqueous silica into wood and other woody tissues such as seed cones. The first study will determine the pathway of silica-laden water in four upright conifer saplings rooted on a sinter apron of a hot spring in Yellowstone National Park, Wyoming, USA. The second study will ascertain whether drip structures seeping out of 17-million year old trees in the Lesvos Petified Forest represent the silica-rich tree sap in the trees when they were still alive, implying that the trees were involved in self-mineralization of their cells. The third study will trace the pathway of silica into allchthonous logs, fossil wood and cones from the sediment substrate. The fourth study will consist of a series of laboratory experiments tracking the pathway of aqueous silica from cell to cell in wood tissues. Using water, powdered volcanic glass, and a heat source, incipient silicification will be produced in various conifer and angiosperm woods of various densities, with and without bark. Pivotal is the orientation of the wood tissue to the flow of aqueous silica. Experiments will also be carried out to induce silicification in branches with bark to show whether bark hinders the entry of silica.Cutting-edge technologies will be applied to the imaging, mapping, and analyzing of the distribution of silica, other minerals, and residual lignin on the micrometer and nanoscale levels. These mostly involve non-invasive, non-destructive methods of surface analysis such as include wave-dispersive X-ray analysis (WDX), confocal Raman spectroscopy (CHRS), X-ray diffraction (XRD), helium ion microscopy (HIM), X-ray photoelectron spectroscopy (XPS), time-of-flight mass spectrometry (ToF-SIMS), and matrix assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-ToF). High-resolution research will also be carried out using scanning electron microscopy, backscattered backscattered electron microscopy, and transmission electron microscopy.