EVOLUTIONARY TRENDS IN THE GENUS GINKGO

Three main independent phylogenetic groups within Ginkgoales , consisting of different families, are suggested. It is considered impossible to deduce the genus Ginkgo from any other genus by means of fossil evidence known at present.
The oldest finds of Ginkgo date from the Lower Jurassic. During the Cretaceous, increasing polymorphy in foliar remains indicates the rise of new species. During the Lower Cretaceous there also appears a type of leaf known both as G. adiantoides and as G. paradiantoides. This leaf is from the gross morphological and the anatomical point of view almost identical with the Tertiary and Recent Ginkgo populations, thus making a direct ancestry between the present-day Ginkgo and those of the Lower Cretaceous likely. By Lower Tertiary times a considerable reduction has taken place leaving only one gross morphological type of leaf, that of G. adiantoides. This is suggested to be identical with G. biloba. Although there is no positive evidence, it can be assumed that the final reduction of the genus, to its present-day East Asiatic home, has taken place during the Pleistocene period.     

The pollen cones of Ginkgo from the Early Cretaceous of China, and their bearing on the evolutionary significance

A well-preserved pollen cone of the genus Ginkgo was found in the Yixian Formation (Early Cretaceous) of Liaoning Province, China, and is described as the new species Ginkgo liaoningensis . The pollen cone, catkin-like, consists of a main axis bearing scales at its base and spirally arranged sporophylls bearing 3–4 (−2) oval or elliptical sporangia. The sporangia are pendulous and dehiscent by a longitudinal slit. The mature pollen grains are monocolpate and elongate-elliptical, and the juvenile pollen grains are found in the tetrad stage. The characteristics of G. liaoningensis are very similar to those of the living Ginkgo biloba , but the sporophylls of G. liaoningensis bear 3–4 (−2) sporangia, whereas those of G. biloba bear mostly two sporangia. G. liaoningensis differs from fossil cones of Ginkgo huttoni from the Jurassic of Yorkshire, UK, and an unnamed specimen of Ginkgo from the Upper Cretaceous of Alberta, Canada, in the size and number of sporangia. The comparison between G. liaoningensis (fossil) and G. biloba (living) supports the reduction hypothesis of ovule organs in Ginkgo , with the number of sporangia having experienced the process of reduction from three or four to two since the Early Cretaceous.  © 2006 The Linnean Society of London, Botanical Journal of the Linnean Society , 2006, 152 , 133–144.     

Evidence for the persistence of wild Ginkgo biloba (Ginkgoaceae) populations in the Dalou Mountains, southwestern China

?Premise of the study: The possible persistence of wild Ginkgo biloba populations in China has long been debated but never scientifically confirmed. We test our hypothesis that the extant Ginkgo populations in the Dalou Mountains (SW China) represent fragments of the original natural Ginkgo range and offer a range of pertinent perspectives on the living fossil Ginkgo's history, prehistory, ecology, and place in human culture-all important aspects of this highly valued species. ?Methods: We analyzed the vegetation of the study area, determined the population age structure of Ginkgo, and compared it to existing fossil records. For supporting material, we also examined records of the lack of human presence before the mid-17th century in the area, the local people's beliefs regarding preservation of the forests and existing genetic studies. ?Key results: Current species composition of Ginkgo forests in the Dalou Mountains agrees closely with floristic assemblages from fossil records bearing G. biloba. Current populations are found in habitats similar to those of fossil Ginkgo, which, as today, favored rock crevices. Female to male ratios are 3:2. Estimated ages for many of the trees show that Ginkgo was present in this area prior to human settlement and indigenous peoples of this area are unlikely to have planted Ginkgo because of traditional beliefs. Our results agree with existing genetic studies that show that these mountains were glacial refugia for G. biloba. ?Conclusions: The corroborative evidence confirms the finding that these populations represent fragments of the original natural Ginkgo in the valley and lower mountain slopes of the Dalou Mountains.     

Palaeophytochemical Constituents of Cretaceous Ginkgo coriacea Florin Leaves

Chemical investigation of the organic solvent extract of Cretaceous Ginkgo coriacea Florin leaves by liquid chromatography-mass spectroscopy （LC-MS） and gas chromatography-mass spectrometry （GC-MS）, analogous to those from extant leaves of Ginkgo biloba L., led to the detection of a group of natural flavonoids and other volatiles. The similarity of the chemical constituents in these two species of Ginkgo suggest that the secondary metabolism of extant G. biloba is close to that of the Cretaceous species. The remaining natural products may be one explanation why the leaves of the Cretaceous G. coriacea have been preserved morphologically in fossilization. The detection of flavonoids suggests that the leaves of G. coriacea experienced a mild post-depositional environment during their fossilization. This appears to be the oldest occurrence of flavonoids in plant fossils.     

Genetic variation of Ginkgo biloba L. (Ginkgoaceae) based on cpDNA PCR-RFLPs: inference of glacial refugia

Ginkgo biloba, a famous living fossil, is the sole survivor of the genus Ginkgo. To make inferences about the glacial refugia that harbored G. biloba, we examined the genetic structure of eight potential refugial populations and plantations using chloroplast DNA (cpDNA) with eight size variants in the trnK1-trnK2 fragment. The data consist of haplotypes from 158 trees collected from eight localities. The majority of the cpDNA haplotypes are restricted to minor portions of the geographical range. Our results suggest that refugia of G. biloba were located in southwestern China. This area is a current biodiversity hotspot of global importance, and may have been protected from the extremes of climatic fluctuations during the Pleistocene. The Ginkgos on West Tianmu Mountain, which were previously considered to be wild by many researchers, may, instead, have been introduced by Buddhist monks.     

New costapalmate palm leaves from the Oligocene Ningming Formation of Guangxi,China, and their biogeographic and palaeoclimatic implications

New palm leaves from the Oligocene Ningming Formation are placed into the morphogenus Sabalites because of their costapalmate leaf shape. Four taxa are described on the basis of leaf compressions with cuticular structure. S. guanxiensis sp. nov. is characterised by hypostomatic leaf blades with a stout costa and a symmetrical base. Sabalites cf. asymmetricus has amphistomatic leaf blades with a long, delicate costa and an asymmetrical base. Sabalites sp. 1 has amphistomatic leaf blades with a long, massive costa and wide segments. Sabalites sp. 2 is characterized by hypostomatic leaf blades with a prominent costa and an asymmetrical base. The four new palm taxa expand our understanding of the floristic elements and features of the Oligocene Ningming flora. Together with the other three palm taxa that were previously reported from the Ningming Formation, our material indicates that the Oligocene Ningming flora had a rich diversity of costapalmate palms. The relatively high species diversity of palms and other plants corroborate that the Oligocene Ningming flora represents a warm and humid climate.     

黑龙江渐新世银杏大化石及其古气候和植物地理意义

首次报道我国渐新世银杏属植物叶化石。化石采自黑龙江汤原县太平川剖面宝泉岭组,角质层保存状态良好。叶为下气孔式。上表皮细胞垂周壁平直,平周壁较平。下表皮大量气孔器不规则地散布于脉间区,形成气孔带;气孔密度约为117个/mm2;气孔器为单环式,保卫细胞下陷,侧副卫细胞角质化强烈并形成乳突。当前材料的形态及显微构造特征与古近纪北半球广泛分布的铁线蕨型银杏Ginkgo adiantoides(Ung.)Heer emend.Flo-rin(auctorum multorum)基本一致。这是我国目前已知年代最新的银杏大化石记录,对于探究银杏属在我国新生代的分布、迁徙以及当时相关的古植物地理和气候环境等具有重要意义。     

A new geranylgeranyl diphosphate synthase gene from Ginkgo biloba, which intermediates the biosynthesis of the key precursor for ginkgolides.

Geranylgeranyl diphosphate synthase (GGPPS, EC: 2.5.1.29) catalyzes the biosynthesis of geranylgeranyl diphosphate (GGPP), which is a key precursor for ginkgolide biosynthesis. Here we reported for the first time the cloning of a new full-length cDNA encoding GGPPS from the living fossil plant Ginkgo biloba. The full-length cDNA encoding G. biloba GGPPS (designated as GbGGPPS) was 1657bp long and contained a 1176bp open reading frame encoding a 391 amino acid protein. Comparative analysis showed that GbGGPPS possessed a 79 amino acid transit peptide at its N-terminal, which directed GbGGPPS to target to the plastids. Bioinformatic analysis revealed that GbGGPPS was a member of polyprenyltransferases with two highly conserved aspartate-rich motifs like other plant GGPPSs. Phylogenetic tree analysis indicated that plant GGPPSs could be classified into two groups, angiosperm and gymnosperm GGPPSs, while GbGGPPS had closer relationship with gymnosperm plant GGPPSs.     

Structure, distribution and taxonomic importance of foliar stomata in some Indian Amaranthaceae

The structure, distribution and taxonomic importance of foliar stomata in 45 taxa belonging to 19 genera have been studied. In all, six stomatal types have been recognized viz., anomocytic, anisocytic, diacytic, paracytic, hemiparacytic and brachyparacytic. The majority of the taxa are amphistomatic whereas hypostomatic leaves are confined to only three taxa. Stomatal diversity is common but most of the taxa show either dominance or codominance. Stomatal distribution is helpful in distinguishing the three tribes of the Amaranthaceae. The tribe Celosieae shows exclusive presence of anomocytic and anisocytic stomata whereas Amarantheae and Gomphreneae show other stomatal types viz., paracytic and diacytic in addition to anomocytic and anisocytic stomata. Further, the latter two tribes are each distinguishable into two subtribes on the basis of stomata.     

银杏与玉米花粉肌动蛋白含量的比较研究

通过免疫印迹鉴定,证明银杏(Ginkgo biloba L.)花粉中存在肌动蛋白。同时对银杏和玉米(Zeamays L.)花粉肌动蛋白含量进行了比较。结果表明,银杏花粉肌动蛋白含量明显少于玉米花粉肌动蛋白含量。SDS-PAGE扫描图谱显示,银杏花粉肌动蛋白含量只有玉米花粉的1/6。两种花粉DNaseⅠ活性抑制结果表明,银杏花粉肌动蛋白含量约为玉米花粉的1/7。     

Reproductive short-shoots of Ginkgo biloba: A quantitative analysis of the disposition of axillary structures

Ginkgo biloba, the only living representative in an otherwise extinct clade, is of pivotal importance to understanding seed plant phylogeny. Although G. biloba and its fossil relatives have been studied for over two centuries, there are both gaps and contradictions in the information available. We present data documenting the distributions of strobili and consider what an understanding of the disposition of strobili along short-shoots in Ginkgo adds to knowledge of the evolution of reproductive structures in seed plants in general. The megasporangiate strobili are found at and around the boundary between bracts and foliage leaves, while the expanse of microsporangiate strobili centers on the fifth bract back from that boundary. Quantitative analysis of the locations of the strobili along the short-shoot finds that increases in numbers of strobili are the result of recruitment of adjacent axils into morphogenetic activity. Gaps in the series of strobili are exceedingly rare. Further, while increased numbers of megasporangiate strobili arise from the symmetrical addition of axils into the fertile zone, increased numbers of microsporangiate strobili arise from a distinctly asymmetrical, basipetally biased, addition of axillary positions. This accurate morphological framework should orient molecular genetic studies that probe gymnosperm development itself or that consider gymnosperms as the proximate sources of gene expression redeployed in the origin of the angiosperm flower.     

Sex-linked photosynthetic physiologic research and the evolutionary ecological analysis in living fossil plant, Ginkgo biloba L.

Ginkgo is an ancient dioecious plant. At present, only Ginkgo biloba L. still exists as a living fossil plant. Botanists have studied it from different aspects in the world due to its unique characteristics. Plant sex physiological ecology is still a knowledge gap in plant ecology. This article measured the photosynthetic traits of adult male and female ginkgoes which grew in suitable environment condition. The result indicated that male and female ginkgoes had similar response to light. The light saturate points (LSP), light compensate point (LCP) and dark respiration rate (Rd) between male and female were also of insignificant differences. However, the net photosynthetic rate (Pn) of female ginkgo was significantly higher than male. From the view of evolution and through comparison with other gymnosperms and angiosperms, the photosynthetic capacity of ginkgo is not obviously lower than that of other plants. It gave us a clue that the photosynthetic capacity was not the direct reason, which restricted the distribution of ginkgo in the Tertiary.     

A New Morphological Interpretation of the Female Reproductive Organs in Ginkgo biloba L., with a Phylogenetic Consideration on Gymnosperms

The ovuliferous structure of Ginkgo biloba L. has been variously interpreted morphologically. As a result the systematic position and the relationship with other gymnosperms of this ancestral gymnosperm have long been under dispute. In the present paper, a brief survey of the main views as to the nature of the ovuliferous structure is givcn. Based on morphological and teratological data previously reported, a new interpretation is proposed. The essential points are summarized as follows: 1. In morphological essence, a fertile dwarf shoot with some ovuliferous structures in Ginkgo biloba L. might as a whole be nothing but a megasporophyll strobilus (female cone), which is shared actually by all the conifers in the gymnosperms. The fertile dwarf shoot has appearance extremely similar to that of the vegetative dwarf shoot, suggesting that in Ginkgo biloba L. the vegetative organs and the reproductive organs have not been yet well differentiated, and thus its megasporophyll strobilus might represent one of the most primitive compound strobilus types. 2. In Ginkgo biloba, the ovuliferous structure borne in the axil of a scale leaf (sometimes a normal leaf) on the dwarf shoot, together with the scale leaf itself, might be the homogenous organ corresponding to the bract-scale and seed-scale complex of the compound female strobilus of the typical conifers. The complex is a relatively isolated reproductive unit on the strobilus. The normal leaves and the scale leaves on the dwarf shoot might be equivalent to the bract-scales in the typical cones, though the normal leaves still retain the vegetative nature as the foliage leaves on the vegetative shoot. The stalk hearing ovules at its top might be equivalent to a seed-scale of the typical cones. 3. The megasporophyll strobilus in Ginkgo biloba, namely a whole fertile dwarf shoot as mentioned above, seems to show much more primitive characteristics than those of typical conifers. In this plant it is very difficult to distinguish the fertile dwarf shoot from the common vegetative dwarf shoot before reproduction time. Moreover, its megasporophyll strobilus often exhibits more atavistic abnormalities than those of other conifers. All the evidence indicates that the primitive ancestor of conifers might have had the fertile organs which might be of basically identical morphology as vegetative shoots, except that in the fertile organs there might exist numerous fertile leaves bearing one or many ovules. 4. The longer stalk of the ovuliferous structure in Ginkgo biloba might have come from mainly a secondary elongation growth of the seed scale, and only a little part of it might be the remains of the original shoot. The fork structure bearing ovules at the top of the stalk might be the rudementary part of the petioles of the only two extremely reduced megasporophylls. The collar around the base of the ovule might be a secondary protective structure. 5. A correct morphological interpretation of the female strobilus in Ginkgo biloba is doubtless of important significance for our better understanding of the evolution of the female reproductive organs in conifers. According to our interpretation mentioned above, together with the concept of the bractscale and seed-scale complex proposed in the present paper, which is mainly based on the concept of the seed-scale complex propose by Florin, here we put forward an evolutionary theory of the bract-scale and seed-scale complex. According to this theory, the female reproductive organs of the ancestral conifers should be very similar, as mentioned above, to the sterile foliage shoot except that the former might have some fertile leaves which could produce ovules at reproduction time. This ancestral female reproductive organ type might have had evolved towards two directions and thus formed two main evolutionary lines. One is represented by the genus Cycas and we may call it the Cycas Evolutionary Line (C-line), in which the megasporophyll strobilus is monopodial, with the fertile leaves and sterile bracts occurring directly on the main axis. The Cycadaceae is the only living gymnosperm member along this evolutionary line. The second line is represented by all the conifers including Ginkgo, which all have the structure of the bract-scale and seed-scale complex, and thus we called it the "Bract-scale and Seed-scale Complex Evolutionary Line" (BS-line). The members along this line have multipodial female strobilus, i.e. compound strobilus. On the main axis occur some sterile vegetative bracts. In the axils of some or most of the bracts occur the seed-scales. The seed-scales are actually the remains of the extremely, or smetimes completely reduced fertile shoots. Each part of the bractt-scale and seed-scale complex and the main axis of the strobilus could have undergone independent or correlated changes, and thus have had formed various types of strobilus which are found in the living conifers. 6. Our theory on the evolution of the bract-scale and seed-scale complex seems to support the division of all the gymnosperms into two major groups as proposed by Chamberlain, and is also in favour of the placement of Ginkgo biloba into the conifers as the most primitive member along BS-line. 7. Based on their similar morphological characters, it can be considered that Ginkgo biloba might have close relationships with the Nageiaceae, Ephedraceae, Welwitschiaceae and Araucariaceae. All these groups have multinerved leaves without costa. These living gymnosperms might have a more direct relationship withthe ancestral cordaites.     

Tertiary leaves of the tribe Banksieae (Proteaceae) from south-eastern Australia

Leaves from the tribe Banksieae of the Proteaceae are well represented in Tertiary deposits in south-eastern Australia. Four new species of Banksieaephyllum are erected, taking the total to 11, and two species are described in a new genus, with leaves with architectural similarities to the tribe Banksieae but without organic preservation. The fossil species demonstrate that the tribe was diverse by the end of the Eocene, but it is difficult to determine the ancestral type from the fossil evidence at present. The vegetation associated with some of the fossil species suggests that the tribe may have had its origins in rainforest, and became adapted to the typically dry, nutrient-poor conditions of sclerophyllous vegetation during the course of the Tertiary.     

STEMS AND LEAVES OF CUNNINGHAMIOSTROBUS GOEDERTII FROM THE OLIGOCENE OF WASHINGTON

This report is based on nine specimens of fossil conifer stems and leaves from the Early Oligocene Jansen Creek Member of the Makah Formation. They were collected along the northern shore of the Olympic Peninsula of Washington. The fossils are preserved as siliceous permineralizations and were exposed in surface view along rock fractures. Details of leaf morphology and epidermal construction appear on fracture surfaces of certain specimens while the cellular construction of the leaves and twigs is visible in thin sections. Leaves are dorsiventrally flattened, attached to twigs that contain up to four growth increments of secondary xylem, up to 2.3 cm long, 3.5 mm wide, and have parallel margins with minute teeth. The leaves are about 0.5 mm thick and have a central vascular strand surrounded by transfusion tissue. A large resin canal occurs abaxial to the vascular strand, and generally two additional resin canals occur in the mesophyll near each leaf margin. Leaves are mostly hypostomatic, with sunken stomata in two longitudinal bands, one to each side of the midline of the leaf and each containing eight to 13 longitudinal rows of stomata. Several unusual anatomical features in the stems also occur in the peduncle and cone axis of seed cones described as Cunninghamiostrobus goedertii, which occurs at the same locality. Thus, the leafy twigs belong to the same species as produced the cones. The cones, leaves, and shoots of this Tertiary conifer are similar to those of modern Cunninghamia but differ from the living species in several respects.     

MULTIVARIATE COMPARISON OF FOSSIL AND RECENT GINKGO WOOD

Multivariate statistical analysis of the anatomical structure of the wood of Recent Ginkgo biloba L. and of fossil Ginkgo beckii Scott, Barghoorn, & Prakash revealed significant differences not apparent through general microscopic observation. On the basis of a multiple discriminant analysis by computer of 10 anatomical characters, the living and fossil Ginkgo woods were separated into two distinct groups. All Recent wood specimens were classified into a single disjoint group by the computer, and all fossil wood specimens were classified into another without misclassifications when all 10 characteristics were included in the analysis. Three characters—number of pits per millimeter of tracheid length on radial wall, ray height, and tangential diameter of late wood tracheids—accounted for most of the discrimination between the two groups.     

Gingkos and multituberculates: evolutionary interactions in the tertiary

The genus Ginkgo is a north temperate gymnosperm taxon represented by fossilized leaves and wood from the early Jurassic through the Pliocene, and by the living species G. biloba native to eastern China. Seeds produced by this widely cultivated tree consist of an odoriferous, vesicatory coat surrounding a hard-shelled "nut." Dispersal of ginkgo seeds is a two step process: repulsion of predators by the toxic coat, followed by attraction of dispersers by the edible "nut." Based on anatomical and distributional evidence, extinct mammalian multituberculates in the genus Ptilodus are plausible consumers and dispersers of ginkgo seeds during the Paleocene and the Eocene. From the Oligocene through Pleistocene, seed-caching rodents are the most likely dispersal agents of ginkgo. Among extant genera in the class Coniferopsida which produce fleshy, animal-dispersed seeds, there appear to be two distinct evolutionary lines: (1) those with relatively large (greater than 20 mm), odoriferous diaspores dispersed primarily by mammals; and (2) those with relatively small (less than 10 mm), visually attractive diaspores dispersed primarily by birds.     

银杏药用物质的开发利用现状及其发展设想

本文概述了银杏叶的药理作用及其开发利用现状。目前,银杏药用物质的获取仍然是通过叶片提取这一途径,这同时存在地理环境、季节等诸多限制因素。而通过银杏组织、细胞培养获得其药用物质的技术研究刚刚起步,距离实际应用仍有相当的距离,但随着这项技术的不断发展,它不仅可用于生产银杏黄酮类和银杏内酯,而且有助于进一步研究银杏所含的特殊化学成分及其相关的代谢途径。     

银杏叶多酚的机械力辅助提取及其体外抗氧化活性研究

为优化银杏叶多酚提取工艺,通过单因素试验考察填充率、球磨转速、球磨时间、乙醇浓度、料液比、提取温度、提取时间七个因素对机械力辅助提取银杏叶多酚得率的影响,以银杏叶多酚得率为响应值,采用Box-Benhnken三因素三水平响应面设计优化工艺,同时比较了4种提取方法对银杏叶多酚提取得率和抗氧化活性的差异。结果表明,机械力辅助提取银杏叶多酚的最佳工艺条件为:填充率26%、球磨转速为400rpm、球磨时间为15min。在此条件下,银杏叶多酚的得率为7.33%。机械力辅助乙醇提取银杏叶多酚得率低于碱水提取法,但是抗氧化活性高于碱水法提取的银杏叶多酚;抗氧化活性与乙醇回流法提取的银杏叶多酚相当,但是提取得率高于乙醇回流法。此提取工艺高效可行,具有一定的参考价值。