Ligrone Roberto, Duckett Jeffrey G
Facoltà di Scienze Ambientali Seconda, Università di Napoli, via Arena 22, 81100 Caserta, Italy.
School of Biological Sciences, Queen Mary & Westfield College, Mile End Road, London, E1 4NS, UK.
New Phytol. 1998 Nov;140(3):567-579. doi: 10.1111/j.1469-8137.1998.00298.x.
Contrary to the long-held belief that, internal to the cortical sterome, the central region of Sphagnum stems comprises unspecialized parenchyma, the present light- and electron-microscope study has revealed that these cells in fact have a highly specialized cytoplasmic organization. Their key features are: (a) the absence of large central vacuoles; (b) a spindle-shaped nucleus positioned internally; (c) a prominent axial system of endoplasmic microtubules associated with the nucleus, mitochondria, pleomorphic vacuoles, and membrane-bounded tubules and vesicles; (d) a distinct cytoplasmic polarization, with the cellular region near the capitulum being richer in organelles than the basal region; and (e) a high frequency of plasmodesmata in the cross walls with an enlarged median region containing no discernible desmotubule. Such a distinctive combination of cytological features has been hitherto only described for putative food-conducting cells in bryoid mosses. The results introduce a major new character common to Sphagnum and bryoid mosses and strongly suggest that this cytological organization underlines cellular specialization in symplasmic transport.
与长期以来的观点相反，即泥炭藓茎的中央区域在皮层组织内部由未特化的薄壁细胞组成，目前的光学显微镜和电子显微镜研究表明，这些细胞实际上具有高度特化的细胞质组织。它们的关键特征是：（a）没有大的中央液泡；（b）内部有一个纺锤形的细胞核；（c）与细胞核、线粒体、多形液泡以及膜结合的小管和囊泡相关的内质微管的突出轴向系统；（d）明显的细胞质极化，靠近头状体的细胞区域比基部区域含有更多的细胞器；（e）横壁中胞间连丝的频率很高，中间区域扩大，没有可辨别的连丝微管。迄今为止，这种独特的细胞学特征组合仅在苔藓类苔藓的假定输导食物的细胞中被描述过。这些结果引入了泥炭藓和苔藓类苔藓共有的一个主要新特征，并强烈表明这种细胞学组织是共质体运输中细胞特化的基础。
