scholarly journals Female Short Shoot and Ovule Development in Ginkgo biloba L. with Emphasis on Structures Associated with Wind Pollination

ISRN Botany ◽  
2012 ◽  
Vol 2012 ◽  
pp. 1-9 ◽  
Author(s):  
Biao Jin ◽  
Di Wang ◽  
Yan Lu ◽  
Xiao Xue Jiang ◽  
Min Zhang ◽  
...  
Keyword(s):  
Ginkgo Biloba ◽  
Mature Stage ◽  
Wind Pollination ◽  
Short Shoot ◽  
Female Cone ◽  
Architectural Features ◽  
Micropylar Canal ◽  
Short Shoots ◽  
Tip Cells

The orientation and morphology of the female cone are important for wind pollination in gymnosperms. To examine the role of female reproductive structures associated with wind pollination in Ginkgo biloba, we used scanning electron microscopy and semithin section techniques to observe the development of female short shoots and ovules in G. biloba before and during the pollination period. The ovule differentiation process was divided into six stages: undifferentiated, general stalk differentiation, integument differentiation, nucellus differentiation, collar differentiation, and mature stage. Before the pollination period, the integument tip generated the micropylar canal and the micropyle, while the nucellus tip cells degenerated to form the pollen chamber. During pollination, the micropylar canal surface became smooth, the micropyle split into several pieces and bore a pollination drop, and the pollen chamber directly faced the straight micropylar canal. The leaves and ovules were spirally arranged on the female short shoot, with the ovules erect and the fan-shaped leaves bent outwards and downwards. The ovules of G. biloba have differentiated some special architectural features adapted for pollen capture and transport. Together, these structures constitute a reproductive structural unit that may improve wind pollination efficiency at the female level.

The Pentoxylon plant

1985 ◽  
Vol 310 (1142) ◽  
pp. 77-108 ◽  
Keyword(s):  
Male Flower ◽  
Short Shoot ◽  
Female Cone ◽  
Leafy Shoots ◽  
Long Shoots ◽  
Short Shoots ◽  
Type 3 ◽  
Head Type

The various dispersed organs belonging to the Pentoxylon plant viz. Pentoxylon (stem), Nipaniophyllum (leaf), Sahnia (male flower) and Carnoconites (female cone) have been studied in detail. Apart from the long shoots (type 1 shoots), the plant bore three different kinds of short shoots: the thick woody short shoots, each with a broadly conical head (type 2 shoots); the slender parenchymatous short shoots (type 3 shoots); and the slightly thicker parenchymatous short shoot (type 4 shoot) terminating in a Sahnia flower. In addition to the well known Nipaniophyllum raoi leaves a second species, N. hobsonii sp. nov., is recognized. In Sahnia the sporangiophores were borne on a collar-like structure formed by the raised margin of the receptacle. The broadly conical head of the thick woody short shoot (type 2 shoot) might be the basis of the cone-bearing branchlets of Carnoconites fruits. The seeds of Carnoconites are spirally arranged rather than being in longitudinal rows as previously suggested. Pentoxylon was probably a shrubby plant which grew beside water. It sent up erect branched leafy shoots which after a few seasons of growth flopped onto the ground or on other stems, making a thicket. Although the stem, Pentoxylon , resembles Medullosa and Rhexoxylon anatomically, the reproductive parts of the plant, Sahnia and Carnoconites , are unlike those of any group of gymnosperms. The Pentoxylon plant is accordingly regarded as an extinct gymnosperm of unknown affinity. Nipanioxylon guptai has previously been regarded as related to Pentoxylon , but its holotype is believed to be a conifer and has nothing to do with the Pentoxylon plant.

Microstructure of high-temperature (>73 °C) siliceous sinter deposited around hot springs and geysers, Yellowstone National Park: the role of biological and abiological processes in sedimentation

2003 ◽  
Vol 40 (11) ◽  
pp. 1611-1642 ◽  
Author(s):  
Donald R Lowe ◽  
Deena Braunstein
Keyword(s):  
High Temperature ◽  
Yellowstone National Park ◽  
National Park ◽  
Hot Springs ◽  
Strain Effect ◽  
Temperature Sinter ◽  
Architectural Features ◽  
Siliceous Sinter ◽  
High Temperature Sinter

Slightly alkaline hot springs and geysers in Yellowstone National Park exhibit distinctive assemblages of high-temperature (>73 °C) siliceous sinter reflecting local hydrodynamic conditions. The main depositional zones include subaqueous pool and channel bottoms and intermittently wetted subaerial splash, surge, and overflow areas. Subaqueous deposits include particulate siliceous sediment and dendritic and microbial silica framework. Silica framework forms thin, porous, microbe-rich films coating subaqueous surfaces. Spicules with intervening narrow crevices dominate in splash zones. Surge and overflow deposits include pool and channel rims, columns, and knobs. In thin section, subaerial sinter is composed of (i) dark brown, nearly opaque laminated sinter deposited on surfaces that evaporate to dryness; (ii) clear translucent silica deposited subaqueously through precipitation driven by supersaturation; (iii) heterogeneous silica representing silica-encrusted microbial filaments and detritus; and (iv) sinter debris. Brownish laminations form the framework of most sinter deposited in surge and overflow zones. Pits and cavities are common architectural features of subaerial sinter and show concave-upward pseudo-cross-laminations and micro-unconformities developed through migration. Marked birefringence of silica deposited on surfaces that evaporate to dryness is probably a strain effect. Repeated wetting and evaporation, often to dryness, and capillary effects control the deposition, morphology, and microstructure of most high-temperature sinter outside of the fully subaqueous zone. Microbial filaments are abundant on and within high-temperature sinter but do not provide the main controls on morphology or structuring except in biofilms developed on subaqueous surfaces. Millimetre-scale lamination cyclicity in much high-temperature sinter represents annual layering and regular seasonal fluctuations in silica sedimentation.

Hypoxia-driven angiogenesis: role of tip cells and extracellular matrix scaffolding

2010 ◽  
pp. 1 ◽  
Author(s):  
Stéphane Germain ◽  
Catherine Monnot ◽  
Laurent Muller ◽  
Anne Eichmann
Keyword(s):  
Extracellular Matrix ◽  
Tip Cells

Effect of Ginkgo biloba extract on rat hepatic microsomal CYP1A activity: role of ginkgolides, bilobalide, and flavonols

2004 ◽  
Vol 82 (1) ◽  
pp. 57-64 ◽  
Author(s):  
I fan Kuo ◽  
Jie Chen ◽  
Thomas K.H Chang
Keyword(s):  
Ginkgo Biloba ◽  
Ginkgo Biloba Extract ◽  
Inhibitory Potency ◽  
Hepatic Microsomes ◽  
Cyp1a Activity ◽  
Ginkgo Biloba Extracts ◽  
The Individual ◽  
Vitro Effect

The present study investigated the in vitro effect of Ginkgo biloba extracts and some of the individual constituents (ginkgolides, bilobalide, and flavonols such as kaempferol, quercetin, isorhamnetin, and their glycosides) on CYP1A-mediated 7-ethoxyresorufin O-dealkylation in hepatic microsomes isolated from rats induced with β-naphthoflavone. G. biloba extract competitively inhibited CYP1A activity, with an apparent Ki value of 1.6 ± 0.4 µg/mL (mean ± SE). At the concentrations present in the G. biloba extracts, ginkgolides A, B, C, and J and bilobalide did not affect CYP1A activity, whereas kaempferol (IC50 = 0.006 ± 0.001 µg/mL, mean ± SE), isorhamnetin (0.007 ± 0.001 µg/mL), and quercetin (0.050 ± 0.003 µg/mL) decreased this activity. The monoglycosides (1 and 10 µg/mL) and diglycosides (10 µg/mL) of kaempferol and quercetin but not those of isorhamnetin also inhibited CYP1A activity. The order of inhibitory potency was kaempferol ~ isorhamnetin > quercetin, and for each of these flavonols the order of potency was aglycone >> monoglycoside > diglycoside. In summary, G. biloba extract competitively inhibited rat hepatic microsomal CYP1A activity, but the effect was not due to ginkgolides A, B, C, or J, bilobalide, kaempferol, quercetin, isorhamnetin, or the respective flavonol monoglycosides or diglycosides.Key words: bilobalide, CYP1A, cytochrome P450, Ginkgo biloba, ginkgolide, flavonol.

Growth and reproductive biology of Joffrea speirsii gen. et sp. nov., a Cercidiphyllum-like plant from the Late Paleocene of Alberta, Canada

1985 ◽  
Vol 63 (2) ◽  
pp. 340-364 ◽  
Author(s):  
Peter R. Crane ◽  
Ruth A. Stockey
Keyword(s):  
Upper Cretaceous ◽  
Constant Field ◽  
Short Shoot ◽  
Early Tertiary ◽  
Late Paleocene ◽  
Large Numbers ◽  
Close Relationship ◽  
Field Association ◽  
Short Shoots ◽  
Floodplain Habitats

Six kinds of angiosperm compression fossils are described from the Paskapoo Formation (Late Paleocene) at Joffre Bridge near Red Deer, Alta. Pistillate inflorescences with attached carpels, folliculate infructescences, seeds, seedlings, leaves, and shoots arc all assigned to Joffrea speirsii gen. et sp. nov. Crane and Stockey. Evidence for treating the different organs under a single binomial includes attachment of inflorescences and leaf petioles to long and short shoot systems, morphological intermediates between carpels and follicles, follicles preserved expelling seeds, seeds preserved during germination, stages in seedling development, similarity between seedling and adult foliage, and constant field association. Joffrea is similar in many respects to the widespread Upper Cretaceous and early Tertiary fossil Nyssidium arcticum (Heer) Iljinskaja. Comparison of Joffrea to the extant genera Cercidiphyllum Siebold et Zuccarini, Trochodendron Siebold et Zuccarini, and Tetracentron Oliver indicates a close relationship to Cercidiphyllum; and Joffrea is interpreted as an extinct representative of the family Cercidiphyllaceae. The fossil material clarifies morphological interpretations of the pistillate reproductive structures in extant Cercidiphyllum. The probable staminate inflorescences of Joffrea, are also similar to extant Cercidiphyllum. They are budlike and composed of 10–20 bracts, some of which have stamens in their axils. Pollen has not been recovered from the anthers. Pistillate inflorescences developed from axillary buds on the short shoots and were probably wind-pollinated. The production of numerous small winged seeds, epigeal germination, and the preservation of large numbers of in situ seedlings suggest that Joffrea speirsii and similar extinct Upper Cretaceous and early Tertiary species may have been "weedy" plants capable of rapidly colonizing open floodplain habitats.

The histone acetyltransferase HBO1 (KAT7) promotes efficient tip cell sprouting during angiogenesis

Development ◽  
2021 ◽  
Author(s):  
Zoe L. Grant ◽  
Peter F. Hickey ◽  
Waruni Abeysekera ◽  
Lachlan Whitehead ◽  
Sabrina M. Lewis ◽  
...  
Keyword(s):  
Histone Acetyltransferase ◽  
Dynamic Changes ◽  
Cell Behaviour ◽  
Tip Cell ◽  
Sprouting Angiogenesis ◽  
A Genome ◽  
Vessel Growth ◽  
Intergenic Regions ◽  
Tip Cells

Blood vessel growth and remodelling are essential during embryonic development and disease pathogenesis. The diversity of endothelial cells (ECs) is transcriptionally evident and ECs undergo dynamic changes in gene expression during vessel growth and remodelling. Here, we investigated the role of the histone acetyltransferase HBO1 (KAT7), which is important for activating genes during development and histone H3 lysine 14 acetylation (H3K14ac). Loss of HBO1 and H3K14ac impaired developmental sprouting angiogenesis and reduced pathological EC overgrowth in the retinal endothelium. Single-cell RNA-sequencing of retinal ECs revealed an increased abundance of tip cells in Hbo1 deleted retinas, which lead to EC overcrowding in the retinal sprouting front and prevented efficient tip cell migration. We found that H3K14ac was highly abundant in the endothelial genome in both intra- and intergenic regions suggesting that the role of HBO1 is as a genome organiser that promotes efficient tip cell behaviour necessary for sprouting angiogenesis.

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