Is there a tapetum in the hornwort capsule? Evidence from the sporogenesis of Phaeoceros

IF 2.3 2区 生物学 Q2 PLANT SCIENCES
Vladimir R Filin, Anna G Platonova
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Abstract

The tapetum is an important tissue in the sporangia of tracheophytes that provides nutrition for developing spores and participates in sporoderm construction, but the data on the tapetum in the sporangia of bryophytes and, in particular, hornworts, are contradictory. Some investigators considered the capsule wall and pseudoelates a tapetum in hornworts, but others suppose that the tapetum is absent in hornwort capsules at all. The structure of the sporocytes and spores, pseudoelaters, the lining layer of the capsule wall, and the outer layer of the columella of Phaeoceros laevis were studied at successive developmental stages by light, fluorescence, and transmission electron microscopy. We revealed that sporocytes accumulate carbohydrates that are required for the construction of the sporoderm and the storage of nutrients in mature spores before the formation of a special wall. Such a feature significantly distinguishes hornworts from mosses and angiosperms. Pseudoelaterocytes and pseudoelaters do not possess any ultrastructural features, indicating that they provide the sporocytes and spores with nutrition. Cells of the lining layer of the capsule wall and the outer layer of the columella do not possess characteristic ultrastructural features of secretory tissue at any developmental stage (in contrast to the moss tapetum), but they apparently participate in the transfer of nutrients in the capsule locule from the foot at the time the sporocytes are actively growing and accumulating nutrients. We accept the strict interpretation of the tapetum as a tissue that lines the capsule locule and has the specialized ultrastructure characteristic of the secretory tissues. Therefore, contrary to the opinion of some researchers, we believe that neither pseudoelaters nor the lining layer of the capsule wall should be considered a tapetum. Columella cells have a structural specialization for upward transport of assimilates, and they should not be regarded as a tapetum. We suppose that tapetum was absent in the common ancestor of the hornworts as well as in the common ancestor of embryophytes.
角草蒴果中是否有绦膜?来自辉石菌孢子发生过程的证据
担子是气管植物孢子囊中的一个重要组织,它为发育中的孢子提供营养,并参与孢子体的构建,但关于真菌纲植物,尤其是角叉菜孢子囊中担子的数据却相互矛盾。一些研究者认为角叉菜的蒴果壁和假髓鞘就是绦膜,但另一些研究者则认为角叉菜蒴果中根本没有绦膜。我们通过光镜、荧光显微镜和透射电子显微镜研究了月芒的孢子细胞和孢子、假elaters、蒴果壁衬里层和荚膜外层在各个发育阶段的结构。我们发现,孢子细胞在形成特殊的孢子壁之前,会积累构建孢子体和储存成熟孢子中营养物质所需的碳水化合物。这一特征将角叉菜与苔藓和被子植物明显区分开来。假胚层细胞和假胚层细胞不具有任何超微结构特征,这表明它们为孢子细胞和孢子提供营养。蒴果壁衬里层和菌褶外层的细胞在任何发育阶段都不具有分泌组织的超微结构特征(与苔藓的绦虫形成鲜明对比),但在孢子细胞积极生长和积累养分时,它们显然参与了从足部向蒴果室转移养分的过程。我们同意将绦膜严格解释为衬垫囊室的组织,并具有分泌组织特有的超微结构。因此,与一些研究人员的观点相反,我们认为假隔膜和蒴果壁的衬里层都不应被视为绦膜。结肠细胞具有向上运输同化物的特殊结构,因此不应被视为绦膜。我们认为,角草的共同祖先和胚状体的共同祖先都不存在绦膜。
本文章由计算机程序翻译,如有差异,请以英文原文为准。
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来源期刊
CiteScore
5.70
自引率
8.30%
发文量
54
审稿时长
3.5 months
期刊介绍: The Botanical Journal of the Linnean Society publishes original papers on systematic and evolutionary botany and comparative studies of both living and fossil plants. Review papers are also welcomed which integrate fields such as cytology, morphogenesis, palynology and phytochemistry into a taxonomic framework. The Journal will only publish new taxa in exceptional circumstances or as part of larger monographic or phylogenetic revisions.
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