Department of Biology and the Burke Museum of Natural History and Culture, University of Washington, Box 351800, Seattle, WA, 98195-1800, USA.
New Phytol. 2019 Mar;221(4):2273-2285. doi: 10.1111/nph.15559. Epub 2018 Nov 26.
Anecdotal evidence indicating substantial silica accumulation in tissues of bryophytes suggests that silica (phytolith) deposition evolved early on in embryophytes. To test this hypothesis, we conducted the first survey of phytolith content representing the major liverwort, moss and hornwort clades. We also assessed the diagnostic value of bryophyte phytoliths. Silica extracted from bryophyte material through wet-ashing was described, focusing on abundance, classifying taxa as nonproducers, light producers and higher producers; and phytolith morphotypes. Ancestral state reconstruction of these characters was performed for mosses and liverworts using published phylogenies. Phytoliths are present in multiple subclades within liverworts, mosses and hornworts, but these phyla were not ancestrally high silica-producers. Higher deposition occurs in liverworts and mosses with specialized water-conducting cells. We hypothesize that active, high silica accumulation was not ancestral for embryophytes, but became possible in clades with increased water conductance. Phytoliths of diagnostic structures (e.g. pegged rhizoids) could help track bryophyte clades or water conductance evolution in the fossil record.
有证据表明，苔藓植物组织中存在大量的硅积累，这表明硅（植硅体）沉积在胚胎植物中很早就进化了。为了验证这一假设，我们对代表主要苔类植物、藓类植物和角苔类植物的主要分支的植硅体含量进行了首次调查。我们还评估了苔藓植物植硅体的诊断价值。通过湿法灰化从苔藓植物材料中提取的硅进行了描述，重点关注丰度、将分类群归类为非生产者、轻度生产者和高度生产者；以及植硅体形态类型。使用已发表的系统发育对苔藓植物和地钱进行了这些特征的祖先状态重建。植硅体存在于苔类植物、藓类植物和角苔类植物的多个亚科中，但这些门并不是硅的高生产者。在具有特殊输水细胞的地钱和藓类植物中，硅的沉积更高。我们假设，积极的、高硅积累对胚胎植物来说并不是原始的，但在输水能力增强的类群中变得可能。具有诊断结构（如钉状假根）的植硅体可以帮助追踪苔藓植物的进化或水传导在化石记录中的演化。
