Carboniferous pteridosperm studies: morphology and anatomy of Schopfiastrum decussatum

1972 ◽  
Vol 50 (12) ◽  
pp. 2649-2658 ◽  
Author(s):  
Gar W. Rothwell ◽  
Thomas N. Taylor
Keyword(s):  
Secondary Xylem ◽  
Vascular Cambium ◽  
Secondary Phloem ◽  
Outer Cortex ◽  
Southern Illinois ◽  
Leaf Arrangement ◽  
Resin Canals ◽  
Inner Cortex

The monostelic seed fern Schopfiastrum decussatum Andrews is described from a specimen collected at a Middle Pennsylvanian petrifaction locality in southern Illinois. The specimen measures 24 cm long and is about 1.1 cm in diameter. Two petioles are attached to the axis and abundant foliar material is also present. Leaf arrangement is alternate and distichous. The stem consists of an exarch protostele surrounded by a prominent zone of secondary xylem. Secondary phloem and a vascular cambium are also preserved. The cortex is characterized by an undulating outer epidermal zone consisting of alternating ridges and furrows; internally this zone is delimited by conspicuous lacunae. Sclerenchyma bands occur in the outer cortex, with prominent resin canals present in the inner cortex. The fronds are represented by dichotomizing rachides, primary pinnae, and laminar pinnules. Features of the plant are compared to those of other Carboniferous pteridosperms, and a reconstruction of Schopfiastrum is included.

Initiation of adventitious root primordia in very young Pinusbanksiana seedling cuttings

1983 ◽  
Vol 13 (1) ◽  
pp. 191-195 ◽  
Author(s):  
Cheryl R. Montain ◽  
Bruce E. Haissig ◽  
John D. Curtis
Keyword(s):  
Transition Zone ◽  
Adventitious Root ◽  
Secondary Xylem ◽  
Vascular Cambium ◽  
Root Initiation ◽  
Secondary Phloem ◽  
Root Primordia ◽  
Cortical Cells ◽  
Parenchyma Cells ◽  
Resin Canals

The present work describes the anatomy of adventitious root initiation in 20-day-old Pinusbanksiana Lamb, seedling cuttings propagated under intermittent mist. Shortly after cuttings were made, basal necrosis occurred in all tissues (epidermis, periderm, cortex, primary and secondary phloem, and vascular cambium) that surrounded the central xylem cylinder. Thereafter, a relatively small "callus complex" composed of parenchyma cells, a few secondary xylem tracheids, and incompletely differentiated callus vascular cambium and periderm developed at the base of cuttings. One or sometimes two root primordia initiated in the transition zone between the lowermost cortical cells of the hypocotyl and the uppermost callus parenchyma cells. Primordia invariably arose just outside one of the four axial resin canals in the hypocotyl. Results suggested that adventitious root primordia may be initiated in P. banksiana cuttings only in association with differentiated or differentiating resin canals.

REACTION TISSUES IN GNETUM GNEMON A PRELIMINARY REPORT

IAWA Journal ◽  
2001 ◽  
Vol 22 (4) ◽  
pp. 401-413 ◽  
Author(s):  
P. B. Tomlinson
Keyword(s):  
Cell Walls ◽  
Tension Wood ◽  
Secondary Xylem ◽  
Secondary Phloem ◽  
Outer Cortex ◽  
Cortical Cells ◽  
Wood Fibres ◽  
Developmental Feature ◽  
Gnetum Gnemon ◽  
Clear Differentiation

Gnetum gnemon exhibits Rouxʼs model of tree architecture, with clear differentiation of orthotropic from plagiotropic axes. All axes have similar anatomy and react to displacement in the same way. Secondary xylem of displaced stems shows little eccentricity of development and no reaction anatomy. In contrast, there is considerable eccentricity in extra-xylary tissue involving both primary and secondary production of apparent tension-wood fibres (gelatinous fibres) of three main kinds. Narrow primary fibres occur concentrically in all axes in the outer cortex as a normal developmental feature. In displaced axes gelatinous fibres are developed abundantly and eccentrically on the topographically upper side, from pre-existing and previously undetermined primary cortical cells. They are wide with lamellate cell walls. In addition narrow secondary phloem fibres are also differentiated abundantly and eccentrically on the upper side of displaced axes. These gelatinous fibres are narrow and without obviously lamellate cell walls. Eccentric gelatinous fibres thus occupy a position that suggests they have the function of tension wood fibres as found in angiosperms. This may be the first report in a gymnosperm of fibres with tension capability. Gnetum gne-mon thus exhibits reaction tissues of unique types, which are neither gymnospermous nor angiospermous. Reaction tissues seem important in maintaining the distinctive architecture of the tree.

Development of Included Phloem in the Stem of Combretum Nigricans (Combretaceae)

IAWA Journal ◽  
1995 ◽  
Vol 16 (2) ◽  
pp. 151-158 ◽  
Author(s):  
R. W. den Outer ◽  
W. L. H. van Veenendaal
Keyword(s):  
Secondary Xylem ◽  
Vascular Cambium ◽  
Secondary Phloem ◽  
Xylem Parenchyma ◽  
Long Period ◽  
Short Period ◽  
Outer Border

The development of diffuse included phloem strands in Combretum nigricans sterns is described, During a short period of time, a small phloem strand is cut off locally in an inward direction by an otherwise normal bidirectional vascular cambium. This contrasts with previous descriptions and interpretations because these strands are not formed after redifferentiation of secondary xylem parenchyma. A complementary cambium formed at the inner border of the young strand somewhat enlarges the strand and, during a relatively long period, produces secondary phloem outwards. Finally this complementary cambium stops functioning as a cambium and merges with the secondary phloem it has produced. Radial rows of cells are present within the included phloem strands which continue into the later-formed secondary xylem; rays transverse the strands. Crushing of the phloem takes place near the outer border of the strand, forming cap-like tissues of disorganized cells.

Differentiation of adventitious root primordia in callus of Pinusbanksiana seedling cuttings

1983 ◽  
Vol 13 (1) ◽  
pp. 195-200 ◽  
Author(s):  
Cheryl R. Montain ◽  
Bruce E. Haissig ◽  
John D. Curtis
Keyword(s):  
Adventitious Root ◽  
Secondary Xylem ◽  
Root Systems ◽  
Vascular Cambium ◽  
Root Primordia ◽  
Specific Identification ◽  
Resin Canals

The root systems of 97-day-old seedlings of Pinusbanksiana Lamb, were severed just below the lowermost needles, and the cuttings were placed in misted propagation benches. A complex of tissues including callus, vascular cambium, secondary xylem, periderm, and resin canals formed at the base of cuttings. Adventitious root primordia were initiated at the periphery of the basal-most portions of this complex in association with resin canals, tracheid "nests", periderm, and, possibly callus vascular cambium. Anatomical complexity of the developing tissues precluded more specific identification of sites of primordium initiation.

Seed fern (Dictyastrum chestriensis n. gen. and sp.) with a Dictyoxylon-type cortex from the Upper Mississippian of the Illinois Basin

1987 ◽  
Vol 61 (1) ◽  
pp. 184-195
Author(s):  
James R. Jennings
Keyword(s):  
Secondary Xylem ◽  
Fiber Bundles ◽  
Illinois Basin ◽  
Outer Cortex ◽  
Type Pattern ◽  
Inner Cortex

Dictyastrum chestriensis n. gen. and sp. is a seed fern that occurs in the Chester Series (Upper Mississippian) of the Illinois Basin, and is based on compressions, impressions, and pyritemarcasite petrifactions of the stem and frond. The stem has a mixed prostele with indistinct protoxylem, and the larger specimens have a thin zone of secondary xylem that contains many small rays. The inner cortex contains numerous transversely-oriented sclerotic nests, whereas the outer cortex contains prominent anastomosing fiber bundles that produce the Dictyoxylon-type pattern that is frequently observable on compressions and impressions. The petiole is massive, has an expanded base, and forks distally into unequal subdivisions. The distal frond has small pinnules with rounded lobes and corresponds to the form species Sphenopteris stricta (=S. bermudensiformis), which is used for isolated compressions and impressions. Dictyastrum chestriensis belongs to the Lyginopteridales and is intermediate morphologically between Lyginopteris and Heterangium.

Wood and Bark Anatomy of Lauraceae. ii. Licaria Aublet

IAWA Journal ◽  
1985 ◽  
Vol 6 (3) ◽  
pp. 187-199 ◽  
Author(s):  
Hans Georg Richter
Keyword(s):  
Diagnostic Tool ◽  
Secondary Xylem ◽  
Secondary Phloem ◽  
Structural Profile ◽  
Quantitative Characters ◽  
Important Diagnostic Tool ◽  
Species Groups ◽  
Bark Anatomy

Qualitative features of the secondary xylem of Licaria present a rather uniform structural profile. Constant differences in primarily quantitative characters lead to the formation of speeies groups wh ich loosely correspond to infrageneric sections based on floral and vegetative morphology. This subdivision is strongly corroborated by the highly variable secondary phloem structurc revealing considerable diversity in type and distribution of sc1erenchymatic tissues. Inorganic inclusions in the secondary xylem, crystals and silica, constitute an important diagnostic tool for differentiating certain species and species groups, but are hardly of importance in the bark.

Seasonal Variation in Traumatic Resin Canal Formation in Chamaecyparis Obtusa Phloem

IAWA Journal ◽  
1998 ◽  
Vol 19 (2) ◽  
pp. 181-189 ◽  
Author(s):  
Keiko Kuroda
Keyword(s):  
Annual Ring ◽  
Stem Canker ◽  
Chamaecyparis Obtusa ◽  
Resin Canal ◽  
Annual Rings ◽  
Secondary Phloem ◽  
Resinous Stem Canker ◽  
Traumatic Resin Canals ◽  
Resin Canals ◽  
Artificial Wounding

Trunks of Chamaecyparis obtusa were injured to examine seasonal differences in traumatic resin canal formation in secondary phloem. Even after wounding during winter, differentiation of axial parenchyma into epithelium was initiated, and vertical resin canals formed. After winter wounding, resin canal development was slower and the tangential extent of resin canals was narrower than after spring wounding, and it took one to two months until resin secretion began. After spring wounding, the sites of resin canal formation were the 1- and 2-year-old annual rings of phloem. In August, the location of resin canal formation shifted into the current and 1-year-old annual ring. Resin canals never formed in secondary phloem areas that were 3 or more years old. In C. obtusa trunks that are affected by the resinous stem canker, numerous tangentiallines of resin canals are found throughout the phloem, not just recent and 1- to 2-year-old phloem. The present research indicates that these many lines of resin canals were not formed at one time, and that the stimuli that induce traumatic resin canals must occur repeatedly over many years. The data on artificial wounding effects are useful for understanding resinous stem canker.

Regeneration of vascular tissue through redifferentiation of interxylary phloem after complete girdling in Aquilaria sinensis

IAWA Journal ◽  
2021 ◽  
pp. 1-16
Author(s):  
Bei Luo ◽  
Arata Yoshinaga ◽  
Tatsuya Awano ◽  
Keiji Takabe ◽  
Takao Itoh
Keyword(s):  
Time Course ◽  
Potential Role ◽  
Vascular Tissue ◽  
Secondary Xylem ◽  
Vascular Cambium ◽  
Aquilaria Sinensis ◽  
Phloem Fibers ◽  
Interxylary Phloem ◽  
Time Course Study

Abstract We studied the time-course of stem response for six months following complete girdling in branches of Aquilaria sinensis to determine the potential role of interxylary phloem (IP) in this response. It was found that the vascular cambium, as well as its derivative secondary xylem and phloem, regenerated fully through redifferentiation of IP. We confirmed that vascular cambium regenerated within one month after girdling based on observation of new vessels, IP, and secondary phloem fibers. The time-course study showed that IPs made connections with each other, merged, and became larger through the proliferation of IPs parenchyma cells and the cleaving of secondary xylem in a narrow zone 400 to 1000 μm deep inside the girdled edge. This led to the formation of a complete circular sheath of vascular cambium, followed by the regeneration of vascular tissue. It is worth noting that the secondary xylem is regenerated always following the formation of a thick belt of wound xylem.

Effects of angiotensin II on regional afferent and efferent arteriole dimensions and the glomerular pole

2000 ◽  
Vol 279 (2) ◽  
pp. R629-R638 ◽  
Author(s):  
Kate M. Denton ◽  
Warwick P. Anderson ◽  
Raja Sinniah
Keyword(s):  
Angiotensin Ii ◽  
Arterial Pressure ◽  
Capillary Pressure ◽  
Ang Ii ◽  
Similar Extent ◽  
Outer Cortex ◽  
Efferent Arteriole ◽  
Vascular Casting ◽  
Cortical Regions ◽  
Inner Cortex

The diversity of renal arteriole diameters in different cortical regions has important consequences for control of glomerular capillary pressure. We examined whether intrarenal angiotensin II (ANG II; 0.1, 1, or 5 ng · kg−1 · min−1) in anesthetized rabbits acts preferentially on pre- or postglomerular vessels using vascular casting. ANG II produced dose-related reductions in afferent and efferent diameters in the outer, mid, and inner cortex, without effecting arterial pressure. Afferent diameter decreased more than efferent in the outer and mid cortex ( P < 0.05) but by a similar extent in juxtamedullary nephrons ( P = 0.58). Calculated efferent resistance increased more than afferent, especially in the outer cortex (127 vs. 24 units; 5 ng · kg−1 · min−1 ANG II). ANG II produced significant dose-related increases in the distance between the arterioles at the entrance to the glomerular pole in all regions. Thus afferent diameter decreased more in response to ANG II, but efferent resistance rose more due to smaller resting luminal dimensions. The results also indicate that glomerular pole dimensions change in response to ANG II.

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