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Zhang W.,Shenyang Institute of Geology and Mineral Resources | Yang X.-J.,CAS Nanjing Institute of Geology and Palaeontology | Fu X.-P.,Shenzhen Fairy Lake Botanical Garden | Zheng S.-L.,Shenyang Institute of Geology and Mineral Resources | And 2 more authors.
Review of Palaeobotany and Palynology | Year: 2012

A new fossil cycad stem Sinocycadoxylon liianum gen. et sp. nov. is described based on a well-preserved petrified specimen collected from the Middle Jurassic of Beipiao, Liaoning Province, China. The stem is composed of a small pith, a polyxylic vascular cylinder and cortex. The pith is parenchymatous with medullary vascular bundles, transfusion cells and mucilage canals. The polyxylic vascular cylinder consists of sixteen centrifugal rings and one centripetal vascular ring, all with distinct growth rings in secondary xylem. The presence of polyxyly with growth rings distinguishes this new genus from all fossil and extant Cycadales. The primary xylem is mesarch. Secondary xylem tracheids have araucarioid radial pitting. The rays are uni- or multiseriate and the latter are usually accompanied by mucilage canals and transfusion cells. This polyxylic stem is believed to be related to the Encephalartoideae of Zamiaceae. The new find provides new insights into cycad evolution which is consistent with former phylogenetic analyses indicating that Cycadales originated form Medullosales. © 2012 Elsevier B.V. Source

He X.,Sun Yat Sen University | Jin J.,Sun Yat Sen University | Wang S.,CAS Institute of Botany | Wang S.,CAS Nanjing Institute of Geology and Palaeontology | And 3 more authors.
International Journal of Plant Sciences | Year: 2010

A marattialean trunk of Psaronius laowujiensis sp. nov. is described from the Upper Permian of the Xuanwei Formation, Panxian County, Guizhou Province, South China. The specimen most likely represents the lower part of the trunk, because the preserved thickness of the root mantel is somewhat larger than the diameter of the stem. Meristeles of the stem are arranged in approximately five tangential stelar cycles but not in radial files. Inner meristeles are in small number, ;12-13, and loosely arranged. Leaf traces diverge helically and are organized in a 2/5 phyllotaxy. The leaf base vascular configuration consists of three strands that include a large U-shaped, centrifugal strand, a small centripetal strand, and an inverted V-shaped internal strand. A vascular bundle sheath one or two cell layers thick surrounds each meristele. Within the centripetal concavity of each peripheral cauline bundle there are anchor-shaped sclerenchymatous strands. Ground tissue appears to consist of aerenchymatous parenchyma, in which secretory cavities are dispersed. Bound roots mostly possess seven to nine protoxylem poles. The vascular bundle sheath is one or two cell layers thick. The inner cortex consists of aerenchymatous parenchyma. A detailed comparison of the present specimen with known species of Psaronius from the Permian of South China is made. Our specimen is similar to Psaronius wangii in many aspects, but the two can be clearly distinguished by the structure of the ground tissue of the stem and the leaf base vascular configuration, which leads to the erection of a new species, P. laowujiensis, for this specimen. Certain important characters in species from the Permian of South China are discussed. The tree- or anchor-shaped sclerenchymatous configuration within the centripetal concavity of the peripheral cauline bundles is unique to species from the South China Permian. The permanent vascular bundle sheath surrounding the meristeles of the stem and the stele of the root is another remarkable feature of those species. The analogous tissue, termed "inner cortex" by certain authors, is also present in some Psaronius from the Euramerican and North China floras, but in those cases it is thinner walled and not as remarkable as the vascular bundle sheath in the species from South China. The leaf base vascular configuration of the species from the Permian in South China is more diverse than those from other places. © 2010 by The University of Chicago. All rights reserved. Source

Kuang D.-Y.,Shenzhen Fairy Lake Botanical Garden | Kuang D.-Y.,South China Agricultural University | Wu H.,South China Agricultural University | Wang Y.-L.,CAS South China Botanical Garden | And 4 more authors.
Genome | Year: 2011

Here, we report a completely sequenced plastome using Illumina/Solexa sequencing-by-synthesis (SBS) technology. The plastome of Magnolia kwangsiensis Figlar & Noot. is 159 667 bp in length with a typical quadripartite structure: 88 030 bp large single-copy (LSC) and 18 669 bp small single-copy (SSC) regions, separated by two 26 484 bp inverted repeat (IR) regions. The overall predicted gene number is 129, among which 17 genes are duplicated in IR regions. The plastome of M. kwangsiensis is identical in its gene order to previously published plastomes of magnoliids. Furthermore, the C-to-U type RNA editing frequency of 114 seed plants is positively correlated with plastome GC content and plastome length, whereas plastome length is not correlated with GC content. A total of 16 potential putative barcoding or low taxonomic level phylogenetic study markers in Magnoliaceae were detected by comparing the coding and noncoding regions of the plastome of M. kwangsiensis with that of Liriodendron tulipifera L. At least eight markers might be applied not only to Magnoliaceae but also to other taxa. The 86 mononucleotide cpSSRs that distributed in single-copy noncoding regions are highly valuable to study population genetics and conservation genetics of this endangered rare species. © 2011 Published by NRC Research Press. Source

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