An ultrastructural study of the araucarian pollen grain Cyclusphaera radiata Archangelsky from the Albian of Patagonia
An ultrastructural study of the araucarian pollen grain Cyclusphaera radiata Archangelsky from the Albian of Patagonia
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DOI：
10.1016/j.revpalbo.2011.12.010
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发表时间：
2012-04-01
影响因子：
1.9
通讯作者：
Archangelsky, Ana
中科院分区：
文献类型：
--
作者：
Del Fueyo, Georgina M.;Archangelsky, Sergio;Archangelsky, Ana
根据阿根廷圣克鲁斯省Albian时代Piedra Clavada组新发现的材料，对原生花粉颗粒cyusphaera radiata Archangelsky进行了修正。采用透射光镜、扫描电镜和透射电镜对花粉的一般形态和超微结构进行了研究。放射状C呈盘状，呈赤道增厚，有两个相对较大的孔，其中一个孔呈放射状增厚，两个中心孔闭塞的伞状结构。下面是一层厚的无定形电子致密层。在这种花粉类型中所看到的特征组合是非常不寻常的，并且在化石或现存的裸子植物颗粒中没有类似的东西。孔内壁的功能解释表明，径向增厚和孔膜参与了协调，萌发过程中有盖状结构，孔内壁可能是一个强化层。本文还提出了一种假设的辐射草传粉机制。这个分类群的古生物地理学表明，在中生代，生产这些谷物的植物居住在冈瓦纳的广阔地区，包括南美洲、非洲、印度和南极洲。(C) 2011 Elsevier B.V.版权所有
The araucarian pollen grain Cyclusphaera radiata Archangelsky is emended based on newly discovered material from the Piedra Clavada Formation of Albian age in Santa Cruz province, Argentina. The general morphology and ultrastructure of the pollen were studied by means of transmitted light, scanning, and transmission electron microscopy. C radiata is discoid with an equatorial thickening and two large opposite apertures, with radial thickenings in one of them and two central apertural occlusive opercula-like structures. Beneath there is a thick amorphous electron-dense nexine. The combination of characters seen in this pollen type is very unusual, and no parallels are known in fossil or extant gymnosperm grains. Functional interpretation of the apertural exine suggests that the radial thickenings and apertural membranes were involved in harmomegthy, the opercula-like structures in germination, and the apertural nexine perhaps as a strengthening layer. A hypothetical pollination mechanism is also presented for C radiata. The paleobiogeography of this taxon shows that during the Mesozoic, the plants that produced these grains inhabited an extensive area of Gondwana that included South America, Africa, India and Antarctica. (C) 2011 Elsevier B.V. All rights reserved.