The Experts below are selected from a list of 360 Experts worldwide ranked by ideXlab platform
Yong Yang - One of the best experts on this subject based on the ideXlab platform.
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Gnetum chinense, a new species of Gnetaceae from southwestern China.
PhytoKeys, 2020Co-Authors: Wei-yin Jin, Chen Hou, Shou-zhou Zhang, Tao Wan, Bing Liu, Yong YangAbstract:Gnetum chinensesp. nov., a new lianoid species of Gnetaceae, is described from southwestern China. The new species is morphologically similar to G. montanum Markgr. in its oblong elliptic leaves and the ovoid to ellipsoid chlamydosperm, but differs from the latter by its shorter male spikes having fewer involucral collars (7-10 vs. 13-18 in G. montanum). We also did a new molecular analysis using one nuclear marker (i.e. nrITS) and four chloroplast markers (i.e. matK gene, rpoC1 intron, psbB-rps12 IGS, and trnF-trnV IGS). The result suggests that this specific clade is sister to a large clade consisting of all other known Chinese lianoid species of Gnetum except G. parvifolium (Warb.) W.C. Cheng.
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ProtoGnetaceae: A new gnetoid macrofossil family from the Jurassic of northeastern China
Perspectives in Plant Ecology Evolution and Systematics, 2017Co-Authors: Yong Yang, Lei Xie, David K. FergusonAbstract:Abstract The divergence of the gnetophytes has been controversial due to the lack of appropriate fossils to calibrate the phylogenetic trees. Here we describe a new macrofossil family, ProtoGnetaceae Y. Yang, L. Xie et D.K. Ferguson, fam. nov., from the Middle Jurassic, consisting of only Protognetum jurassicum Y. Yang, L. Xie et D.K. Ferguson, gen. et sp. nov. This monotypic family displays transitional morphology between Ephedraceae and Gnetaceae. It is similar to the Ephedraceae in the longitudinally striated twigs, the linear parallel-veined leaves decussate at the swollen nodes, and to the Gnetaceae in the lax female spikes and a few sessile female reproductive units (FRUs) verticillately arranged at the nodes. These FRUs are subtended by leaf-like linear bracts, and have an apical short and straight tube. The ProtoGnetaceae provide new evidence to understand the early evolution of the gnetophytes. We reconstructed a phylogeny of gymnosperms based on six DNA markers, and dated the divergence of the gnetophytes with calibration using our new macrofossil. We found that the crown age of the gnetophytes is in the Middle Triassic, the age of modern Ephedra is in the Neogene, and modern Gnetum is dated back to the K/T boundary.
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A new gnetalean macrofossil from the Early Cretaceous and its evolutionary significance
Cretaceous Research, 2017Co-Authors: Yong Yang, Longbiao Lin, David K. Ferguson, Shou-zhou Zhang, Tao WanAbstract:Modern gnetophytes consist of three families, i.e. the Ephedraceae, the Gnetaceae, and the Welwitschiaceae, which show diversified morphology. The basal group Ephedraceae possesses an extremely reduced female cone with only the uppermost pair/whorl being fertile, while both the Gnetaceae and the Welwitschiaceae bear female cones/spikes with multiple whorls of fertile bracts. Here, we describe a new ephedroid macrofossil, Liaoningia decussata Yang et Lin, gen. et sp. nov., from the Lower Cretaceous Yixian Formation of western Liaoning in China. This species has typical ephedroid morphology, e.g. the dichasial branching shoot system, swollen nodes, internodes having many fine longitudinal striations, and decussate phyllotaxy, lengthy linear leaves possessing two parallel veins, and female cones consisting of paired bracts. This new genus is similar to the Ephedraceae in its vegetative organs, but differs from the latter by the female spikes with multiple pairs of fertile bracts. In this respect Liaoningia is similar to both the Gnetaceae and the Welwitschiaceae, but distinctly differs from the latter two genera in its vegetative organs. As a result, our new genus shows intermediate morphology between the Ephedaceae and the other two families of the gnetophytes, and is probably a missing link in the evolutionary process from the Ephedraceae to the clade including the Gnetaceae and the Welwitschiaceae.
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Chengia laxispicata gen. et sp. nov., a new ephedroid plant from the Early Cretaceous Yixian Formation of western Liaoning, Northeast China: evolutionary, taxonomic, and biogeographic implications
BMC Evolutionary Biology, 2013Co-Authors: Yong Yang, Longbiao Lin, Qi WangAbstract:Background: The extant Gnetales include three monotypic families, namely, Ephedraceae (Ephedra), Gnetaceae (Gnetum), and Welwitschiaceae (Welwitschia), all of which possess compound female cones that comprise a main axis and 1 to multiple pairs/whorls of bracts subtending a female reproductive unit or having lower pairs/whorls of bracts sterile. However, the evolutionary origin of such a reproductive architecture in Gnetales is controversial in the light of the competing anthophyte versus gnetifer hypotheses of seed plant relationships. Hence, macrofossils demonstrating the structure of compound female cones of the Gnetales should be important to decipher the early evolution of the order. Results: A new ephedroid plant Chengia laxispicata gen. et sp. nov. is described from the Early Cretaceous Yixian Formation of western Liaoning, Northeast China. The fossil represents a part of a leafy shooting system with reproductive organs attached. The main shoot bears internodes and swollen nodes, from which lateral branches arise oppositely. Reproductive organs consist of female spikes terminal to twigs or axillary to linear leaves. Spikes are loosely arranged, having prominent nodes and internodes. Bracts of the spikes are decussately opposite and comprise 4—8 pairs of bracts. Each bract subtends an ellipsoid seed. Seeds are sessile, with a thin outer envelope and a distal micropylar tube. Conclusions: Chengia laxispicata gen. et sp. nov. provides a missing link between archetypal fertile organs in the crown lineage of the Gnetales and compound female cones of the extant Ephedraceae. Combined with a wealth of Ephedra and ephedroid macrofossils from the Early Cretaceous, we propose a reduction and sterilization hypothesis that the female cone of the extant Ephedraceae may have stemmed from archetypal fertile organs in the crown lineage of the Gnetales. These have undergone sequentially intermediate links similar to female cones of Cretaceous Siphonospermum, Chengia ,a ndLiaoxia by reduction and sterilization of the lower fertile bracts, shortenings of internodes and peduncles as well as loss of reproductive units in all inferior bracts. The basal family Ephedraceae including Ephedra of the extant Gnetales was demonstrated to have considerable diversity by the Early Cretaceous, so an emended familial diagnosis is given here. The Jehol Biota in Northeast China and adjacent areas contains a plethora of well-preserved macrofossils of Ephedra and ephedroids that show different evolutionary stages including primitive and derived characters of Ephedraceae, so Northeast China and adjacent areas may represent either the centre of origination or one of the centres for early diversification of the family.
Jeffrey S. Carmichael - One of the best experts on this subject based on the ideXlab platform.
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Development of sterile ovules on bisexual cones of Gnetum gnemon (Gnetaceae).
American Journal of Botany, 2001Co-Authors: Courtney J. Haycraft, Jeffrey S. CarmichaelAbstract:Angiosperms and Gnetales (Ephedra, Gnetum, Welwitschia ) represent the only seed plants that regularly produce bisexual cones. Unfortunately, the fertility and function of ovules formed on bisexual cones of Gnetales have remained unclear. Some reports indicate that the ovules are sterile while others indicate that they may develop into seeds. This study demonstrates three different developmental patterns of ovules formed on bisexual cones of Gnetum gnemon.Type I ovules did not develop at all after pollination and represented the majority of ovules on each cone. Type II ovules enlarged slightly after pollination due to the enlargement of nucellar tissue. Type III ovules were typically found on the terminal whorl and developed into seed-like structures. The enlargement was due to proliferation of megagametophyte tissue. Sectioned material revealed that megagametophytes show altered development compared to those found in functional female ovules. None of the ovules studied contained embryos, and thus all were sterile. Densitometry of 49,6-diamidino2-phenylindole (DAPI)- stained sections revealed that megagametophyte nuclei formed in the sterile ovules are unreduced (diploid) and thus do not form viable female gametes.
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Development of sterile ovules on bisexual cones of Gnetum gnemon (Gnetaceae).
American Journal of Botany, 2001Co-Authors: Courtney J. Haycraft, Jeffrey S. CarmichaelAbstract:Angiosperms and Gnetales (Ephedra, Gnetum, Welwitschia ) represent the only seed plants that regularly produce bisexual cones. Unfortunately, the fertility and function of ovules formed on bisexual cones of Gnetales have remained unclear. Some reports indicate that the ovules are sterile while others indicate that they may develop into seeds. This study demonstrates three different developmental patterns of ovules formed on bisexual cones of Gnetum gnemon.Type I ovules did not develop at all after pollination and represented the majority of ovules on each cone. Type II ovules enlarged slightly after pollination due to the enlargement of nucellar tissue. Type III ovules were typically found on the terminal whorl and developed into seed-like structures. The enlargement was due to proliferation of megagametophyte tissue. Sectioned material revealed that megagametophytes show altered development compared to those found in functional female ovules. None of the ovules studied contained embryos, and thus all were sterile. Densitometry of 49,6-diamidino2-phenylindole (DAPI)- stained sections revealed that megagametophyte nuclei formed in the sterile ovules are unreduced (diploid) and thus do not form viable female gametes.
Qi Wang - One of the best experts on this subject based on the ideXlab platform.
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Chengia laxispicata gen. et sp. nov., a new ephedroid plant from the Early Cretaceous Yixian Formation of western Liaoning, Northeast China: evolutionary, taxonomic, and biogeographic implications
BMC Evolutionary Biology, 2013Co-Authors: Yong Yang, Longbiao Lin, Qi WangAbstract:Background: The extant Gnetales include three monotypic families, namely, Ephedraceae (Ephedra), Gnetaceae (Gnetum), and Welwitschiaceae (Welwitschia), all of which possess compound female cones that comprise a main axis and 1 to multiple pairs/whorls of bracts subtending a female reproductive unit or having lower pairs/whorls of bracts sterile. However, the evolutionary origin of such a reproductive architecture in Gnetales is controversial in the light of the competing anthophyte versus gnetifer hypotheses of seed plant relationships. Hence, macrofossils demonstrating the structure of compound female cones of the Gnetales should be important to decipher the early evolution of the order. Results: A new ephedroid plant Chengia laxispicata gen. et sp. nov. is described from the Early Cretaceous Yixian Formation of western Liaoning, Northeast China. The fossil represents a part of a leafy shooting system with reproductive organs attached. The main shoot bears internodes and swollen nodes, from which lateral branches arise oppositely. Reproductive organs consist of female spikes terminal to twigs or axillary to linear leaves. Spikes are loosely arranged, having prominent nodes and internodes. Bracts of the spikes are decussately opposite and comprise 4—8 pairs of bracts. Each bract subtends an ellipsoid seed. Seeds are sessile, with a thin outer envelope and a distal micropylar tube. Conclusions: Chengia laxispicata gen. et sp. nov. provides a missing link between archetypal fertile organs in the crown lineage of the Gnetales and compound female cones of the extant Ephedraceae. Combined with a wealth of Ephedra and ephedroid macrofossils from the Early Cretaceous, we propose a reduction and sterilization hypothesis that the female cone of the extant Ephedraceae may have stemmed from archetypal fertile organs in the crown lineage of the Gnetales. These have undergone sequentially intermediate links similar to female cones of Cretaceous Siphonospermum, Chengia ,a ndLiaoxia by reduction and sterilization of the lower fertile bracts, shortenings of internodes and peduncles as well as loss of reproductive units in all inferior bracts. The basal family Ephedraceae including Ephedra of the extant Gnetales was demonstrated to have considerable diversity by the Early Cretaceous, so an emended familial diagnosis is given here. The Jehol Biota in Northeast China and adjacent areas contains a plethora of well-preserved macrofossils of Ephedra and ephedroids that show different evolutionary stages including primitive and derived characters of Ephedraceae, so Northeast China and adjacent areas may represent either the centre of origination or one of the centres for early diversification of the family.
Dedy Darnaedi - One of the best experts on this subject based on the ideXlab platform.
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Stilbene derivatives from Gnetum gnemon Linn.
Phytochemistry, 2003Co-Authors: Ibrahim Iliya, Zulfiqar Ali, Toshiyuki Tanaka, Munekazu Iinuma, Miyuki Furusawa, Ken-ichi Nakaya, Jin Murata, Dedy Darnaedi, Nobuyasu Matsuura, Makoto UbukataAbstract:Four stilbene derivatives, gnemonols K and L (resveratrol trimers), M (isorhapontigenin dimer), and gnemonoside K (glucoside of resveratrol trimer) together with eleven known stilbenoids and a lignan were isolated from the acetone, methanol and 70% methanol soluble parts of the root of Gnetum gnemon (Gnetaceae). The structures of the isolates were determined by spectral analysis. The antioxidant activity of the stilbenoids on lipid peroxide inhibition and super oxide scavenging activity were also investigated.
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Stilbene Derivatives from Two Species of Gnetaceae
Chemical & pharmaceutical bulletin, 2002Co-Authors: Ibrahim Iliya, Zulfiqar Ali, Toshiyuki Tanaka, Munekazu Iinuma, Ken-ichi Nakaya, Jin Murata, Miyuki Furasawa, Yoshiaki Shirataki, Dedy DarnaediAbstract:Five new stilbene oligomers (gnemonols A, B and C, gnemonoside E and gnetal) were isolated together with 2b-hydroxyampelopsin F and gnetin E from Gnetum gnemon and G. gnemonoides. The structures of the compounds were elucidated on the basis of spectral evidence.
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Stilbenoids from the stem of Gnetum latifolium (Gnetaceae).
Phytochemistry, 2002Co-Authors: Ibrahim Iliya, Zulfiqar Ali, Toshiyuki Tanaka, Munekazu Iinuma, Miyuki Furusawa, Ken-ichi Nakaya, Jin Murata, Dedy DarnaediAbstract:Abstract An acetone extract of the stem of Gnetum latifolium Blume afforded the stilbene trimer (latifolol) together with five known stilbenoids (gnetin E, gnetin D, gnetin C, (−)e-viniferin and resveratrol). Their structures were elucidated on the basis of spectral evidence, in particular by using 2D NMR methods.
Courtney J. Haycraft - One of the best experts on this subject based on the ideXlab platform.
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Development of sterile ovules on bisexual cones of Gnetum gnemon (Gnetaceae).
American Journal of Botany, 2001Co-Authors: Courtney J. Haycraft, Jeffrey S. CarmichaelAbstract:Angiosperms and Gnetales (Ephedra, Gnetum, Welwitschia ) represent the only seed plants that regularly produce bisexual cones. Unfortunately, the fertility and function of ovules formed on bisexual cones of Gnetales have remained unclear. Some reports indicate that the ovules are sterile while others indicate that they may develop into seeds. This study demonstrates three different developmental patterns of ovules formed on bisexual cones of Gnetum gnemon.Type I ovules did not develop at all after pollination and represented the majority of ovules on each cone. Type II ovules enlarged slightly after pollination due to the enlargement of nucellar tissue. Type III ovules were typically found on the terminal whorl and developed into seed-like structures. The enlargement was due to proliferation of megagametophyte tissue. Sectioned material revealed that megagametophytes show altered development compared to those found in functional female ovules. None of the ovules studied contained embryos, and thus all were sterile. Densitometry of 49,6-diamidino2-phenylindole (DAPI)- stained sections revealed that megagametophyte nuclei formed in the sterile ovules are unreduced (diploid) and thus do not form viable female gametes.
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Development of sterile ovules on bisexual cones of Gnetum gnemon (Gnetaceae).
American Journal of Botany, 2001Co-Authors: Courtney J. Haycraft, Jeffrey S. CarmichaelAbstract:Angiosperms and Gnetales (Ephedra, Gnetum, Welwitschia ) represent the only seed plants that regularly produce bisexual cones. Unfortunately, the fertility and function of ovules formed on bisexual cones of Gnetales have remained unclear. Some reports indicate that the ovules are sterile while others indicate that they may develop into seeds. This study demonstrates three different developmental patterns of ovules formed on bisexual cones of Gnetum gnemon.Type I ovules did not develop at all after pollination and represented the majority of ovules on each cone. Type II ovules enlarged slightly after pollination due to the enlargement of nucellar tissue. Type III ovules were typically found on the terminal whorl and developed into seed-like structures. The enlargement was due to proliferation of megagametophyte tissue. Sectioned material revealed that megagametophytes show altered development compared to those found in functional female ovules. None of the ovules studied contained embryos, and thus all were sterile. Densitometry of 49,6-diamidino2-phenylindole (DAPI)- stained sections revealed that megagametophyte nuclei formed in the sterile ovules are unreduced (diploid) and thus do not form viable female gametes.