Abstract Phytoliths are microscopic siliceous particles that precipitate within epidermal cells of plant leaves. Phytolith morphology and its carbon isotopic composition (δ13C) are often used to understand the past vegetation composition. To extract phytoliths from modern plants, two different wet-oxidation, dry ashing and microwave digestion techniques have been used. However, the impact of these techniques on the δ13C value of phytoliths of different plant species (trees, shrubs and grasses) is not well understood. The present study compares the recovered materials (RM) from these four extraction methods by scanning electron microscope (SEM) and carbon isotopic composition (δ13CRM). We find that the recovery yield is high in one of the wet-oxidation methods, showing significant organic residues (tissues) as evident from the SEM images. In other three methods, the SEM images show near-complete removal of bulk plant residues. However, the wide variation (up to 14‰) seen in the δ13CRM values (even within a species) suggests a difference in response of bulk tissues and phytoliths towards the extraction methods. The difference in organic constituents within the cell wall and lumen phytoliths also possibly contribute to the variation in δ13CRM values. The characteristic difference observed in 13C/12C ratio between the RM and bulk tissue (Δ13CRM-Bulk) suggests the predominance of lumen phytoliths in grasses and cell wall phytoliths in trees/shrubs species. Since the same extraction methods are also used to remove the organic residues adhering to the phytoliths in soils/paleosols, careful consideration is required before employing phytolith δ13C value for vegetation reconstruction in paleoecological and archeological studies.

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植硅体中吸留碳的碳同位素组成：植硅体提取方法的比较研究

摘要 植硅体是沉淀在植物叶片表皮细胞内的微小硅质颗粒。植硅体形态及其碳同位素组成 (δ13C) 通常用于了解过去的植被组成。为了从现代植物中提取植硅体，已经使用了两种不同的湿氧化、干灰化和微波消化技术。然而，这些技术对不同植物物种（乔木、灌木和草）植硅体 δ13C 值的影响尚不清楚。本研究通过扫描电子显微镜 (SEM) 和碳同位素组成 (δ13CRM) 比较了从这四种提取方法中回收的材料 (RM)。我们发现其中一种湿式氧化方法的回收率很高，从 SEM 图像中可以看出明显的有机残留物（组织）。在其他三种方法中，SEM 图像显示几乎完全去除了大量植物残留物。然而，δ13CRM 值（甚至在一个物种内）中看到的广泛变化（高达 14‰）表明大块组织和植硅体对提取方法的响应存在差异。细胞壁和管腔植硅体内有机成分的差异也可能导致 δ13CRM 值的变化。在 RM 和大块组织 (Δ13CRM-Bulk) 之间观察到的 13C/12C 比率的特征差异表明草中的管腔植硅体和树木/灌木物种中的细胞壁植硅体占优势。由于同样的提取方法也用于去除土壤/古土壤中附着在植硅体上的有机残留物，