Initiation and structure of the secondary vascular system in Phytolacca dioica (Phytolaccaceae)

1984 ◽  
Vol 62 (12) ◽  
pp. 2580-2586 ◽  
Author(s):  
Bruce K. Kirchoff ◽  
Abraham Fahn
Keyword(s):  
Vascular System ◽  
Secondary Growth ◽  
Tissue Response ◽  
Vascular Cambium ◽  
Vascular Cylinder ◽  
Primary Growth ◽  
Secondary Thickening ◽  
Dividing Cells ◽  
Cathodic Side ◽  
Vascular Connections

Phytolacca dioica (L.) is characterized by anomalous secondary thickening by means of supernumerary cambia. After a period of primary growth and the formation of an initial (normal) vascular cambium, supernumerary cambia are initiated outside of the primary vascular cylinder. The initiation of the first supernumerary cambium takes place through approximately the number of nodes equal to the denominator of the phyllotactic fraction characterizing a given axis. At each node a segment of supernumerary cambium is initiated opposite the leaf traces supplying the leaf inserted at that node. The segments of differentiated cambium are preceded by regions of obliquely and anticlinally dividing cells. In the single juvenile axis studied supernumerary cambial segments also appear above the node to the cathodic side of the entering leaf traces, and opposite the medullary bundle immediately anodic to these traces. Vascular connections among the primary and supernumerary vascular cylinders occur between leaf insertions on the same orthostichy. The levels at which these connections occur vary among stems. The switch from ordinary to anomalous secondary growth may be caused by a change in tissue response to stimuli produced by leaves.

scholarly journals Morphoanatomy of the stem in Cyperaceae

2009 ◽  
Vol 23 (3) ◽  
pp. 889-901 ◽  
Author(s):  
Ana Claudia Rodrigues ◽  
Maria Emília Maranhão Estelita
Keyword(s):  
Apical Meristem ◽  
Vascular System ◽  
Secondary Growth ◽  
Cyperus Rotundus ◽  
External Morphology ◽  
Life Phase ◽  
Secondary Thickening ◽  
Primary Body ◽  
Stem Type ◽  
Phase Activity

Cyperaceae are usually perennial, with underground stems mainly rhizomatous, however, other stem types may also occur, such as corms and tubers. The underground stems of five Cyperaceae species were examined. Cyperus rotundus and Fuirena umbellata have plagiotropic rhizomes, while C. esculentus, C. odoratus, Hypolytrum schraderianum and Bulbostylis paradoxa have orthotropic rhizomes. Corms occur in C. rotundus and C. esculentus, and stolons in C. esculentus. The primary body originates from the activity of the apical meristem and later, from the primary thickening meristem (PTM). Secondary growth results from secondary thickening meristem (STM) activity, and occurs in rhizomes of H. schraderianum, B. paradoxa, C. odotarus and F. umbellata. The procambium and the PTM give rise to collateral bundles in H. schraderianum, and amphivasal bundles in the remaining species. The STM gives rise to the vascular system with the associated phloem and xylem. According to our results, the concept of stem type in Cyperaceae depends on external morphology, function, life phase, activity of the thickening meristems and the relative amount of parenchyma.

The continuity of primary and secondary growth in Cordyline terminalis (Agavaceae)

1985 ◽  
Vol 63 (11) ◽  
pp. 1907-1913 ◽  
Author(s):  
Darleen A. DeMason ◽  
Mark. A. Wilson
Keyword(s):  
Vascular System ◽  
Secondary Growth ◽  
Central Cylinder ◽  
Vascular Bundles ◽  
Outer Cortex ◽  
Azure B ◽  
Secondary Thickening ◽  
Radial Extent ◽  
Secondary Tissue ◽  
Wide Zone

The primary thickening meristem in Cordyline terminalis (L.) Kunth was found to be continuous with the secondary thickening meristem in vegetative shoots. This could be seen in longitudinal and transverse sections stained with azure B, aniline blue–black, or safranin and fast green. The primary thickening meristem was a wide zone in the crown, and initial cells were arranged in anticlinal files which were continuous from an area within the central cylinder to the outer cortex. The secondary thickening meristem was narrow in radial extent and consisted of initial cells which were arranged in short, anticlinal files. When vascular bundles were followed (and plotted) acropetally from serial transverse sections starting with groups of anastomosing secondary bundles, secondary bundles were continuous with both major and minor axial primary bundles or with procambial strands. All bundles were collateral in the crown but became amphivasal in the intermediate region of the central cylinder and remained so in the secondary tissue. Procambial strands ran along or within the thickening meristem at all levels of the stem. These observations lead us to believe that in Cordyline terminalis (i) the primary and secondary thickening meristems function as a single entity and (ii) the primary and secondary bundles describe a single, continuus vascular system.

Vascular cambium necrosis in forest fires: using hyperbolic temperature regimes to estimate parameters of a tissue-response model

2004 ◽  
Vol 52 (6) ◽  
pp. 757 ◽  
Author(s):  
M. B. Dickinson ◽  
J. Jolliff ◽  
A. S. Bova
Keyword(s):  
Pinus Ponderosa ◽  
Forest Fires ◽  
Ponderosa Pine ◽  
Process Model ◽  
Acer Rubrum ◽  
Tissue Response ◽  
Vascular Cambium ◽  
Red Maple ◽  
Fixed Temperature ◽  
Temperature Regimes

Hyperbolic temperature exposures (in which the rate of temperature rise increases with time) and an analytical solution to a rate-process model were used to characterise the impairment of respiration in samples containing both phloem (live bark) and vascular-cambium tissue during exposures to temperatures such as those experienced by the vascular cambium in tree stems heated by forest fires. Tissue impairment was characterised for red maple (Acer rubrum), chestnut oak (Quercus prinus), Douglas fir (Pseudotsuga menziesii), and ponderosa pine (Pinus ponderosa) samples. The estimated temperature dependence of the model’s rate parameter (described by the Arrhenius equation) was a function of the temperature regime to which tissues were exposed. Temperatures rising hyperbolically from near ambient (30°C) to 65°C produced rate parameters for the deciduous species that were similar at 60°C to those from the literature, estimated by using fixed temperature exposures. In contrast, samples from all species showed low rates of impairment, conifer samples more so than deciduous, after exposure to regimes in which temperatures rose hyperbolically between 50 and 60°C. A hypersensitive response could explain an early lag in tissue-impairment rates that apparently caused the differences among heating regimes. A simulation based on stem vascular-cambium temperature regimes measured during fires shows how temperature-dependent impairment rates can be used to predict tissue necrosis in fires. To our knowledge, hyperbolic temperature exposures have not been used to characterise plant tissue thermal tolerance and, given certain caveats, could provide more realistic data more efficiently than fixed-temperature exposures.

scholarly journals Comparative stages of atretic oocytes between Episesarma versicolor and E. singaporense from Thailand: Implication on the reproductive success

2020 ◽  
Vol 19 (1) ◽  
pp. 75-86
Author(s):  
Chanyut Sudtongkong ◽  
◽  
Sinlapachai Senarat ◽  
Supparat Kong-oh ◽  
Pisit Poolprasert ◽  
...  
Keyword(s):  
Reproductive Success ◽  
Secondary Growth ◽  
Follicular Cell ◽  
Ovarian Maturation ◽  
Natural Habitats ◽  
Degenerative Process ◽  
Mangrove Area ◽  
Primary Growth

Informative reviews on the oocyte atresia referring to degeneration and resorptive mechanism are warranted in common animals, but it is rarely still found in carbs. In this current study, we focused on characteristics and stage of the atretic oocyte from two important female sesarmid carbs (violet vinegar crab, Episesarma versicolor, and Singapore vinegar crab, E. singaporense) during ovarian maturation. A total of 30 female samples in each carb species were collected from the Palian mangrove area of Trang province, Thailand. The results shared among those carb samples that both primary growth (PGs) and secondary growth (SGs) phases underwent a degenerative process of atresia. The latter of atresia during SGs was also divided into five stages (I, II, III, IV, and V). The degeneration of follicular cell and yolk architecture identifying in the SGs were highlighted. The number of atresias was slightly compared between E. versicolor and E. singaporense; therefore, there were no significant differences. Our observation suggested that the low number of atresia might be associated with the increased reproductive success of two female sesarmid carb living in natural habitats.

Shade avoidance responses are mediated by the ATHB-2 HD-zip protein, a negative regulator of gene expression

Development ◽  
1999 ◽  
Vol 126 (19) ◽  
pp. 4235-4245 ◽  
Author(s):  
C. Steindler ◽  
A. Matteucci ◽  
G. Sessa ◽  
T. Weimar ◽  
M. Ohgishi ◽  
...  
Keyword(s):  
Gene Expression ◽  
Cell Proliferation ◽  
Cell Expansion ◽  
Lateral Root ◽  
Vascular System ◽  
Secondary Growth ◽  
Negative Regulator ◽  
Specific Cell ◽  
Shade Avoidance ◽  
Growth Responses

The ATHB-2 gene encoding an homeodomain-leucine zipper protein is rapidly and strongly induced by changes in the ratio of red to far-red light which naturally occur during the daytime under the canopy and induce in many plants the shade avoidance response. Here, we show that elevated ATHB-2 levels inhibit cotyledon expansion by restricting cell elongation in the cotyledon-length and -width direction. We also show that elevated ATHB-2 levels enhance longitudinal cell expansion in the hypocotyl. Interestingly, we found that ATHB-2-induced, as well as shade-induced, elongation of the hypocotyl is dependent on the auxin transport system. In the root and hypocotyl, elevated ATHB-2 levels also inhibit specific cell proliferation such as secondary growth of the vascular system and lateral root formation. Consistent with the key role of auxin in these processes, we found that auxin is able to rescue the ATHB-2 lateral root phenotype. We also show that reduced levels of ATHB-2 result in reciprocal phenotypes. Moreover, we demonstrate that ATHB-2 functions as a negative regulator of gene expression in a transient assay. Remarkably, the expression in transgenic plants of a derivative of ATHB-2 with the same DNA binding specificity but opposite regulatory properties results in a shift in the orientation of hypocotyl cell expansion toward radial expansion, and in an increase in hypocotyl secondary cell proliferation. A model of ATHB-2 function in the regulation of shade-induced growth responses is proposed.

Vascular System of the Stem of the Wheat Plant. I. Mature State

1972 ◽  
Vol 20 (1) ◽  
pp. 49 ◽  
Author(s):  
JW Patrick
Keyword(s):  
Triticum Aestivum ◽  
Vascular System ◽  
Wheat Plant ◽  
Triticum Aestivum L ◽  
Vascular Bundles ◽  
Vascular Connections ◽  
Main Tiller

The courses of the various vascular bundles in the nodes of the main tiller of Triticum aestivum L. have been reconstructed from anatomical observations of con- secutive serial transverse sections. Of the bundles entering a node (n) from its attached leaf, the first-formed and largest, the median, passes directly through the node to the second node below (n-2), where it bifurcates and fuses with other strands. These continue to node n- 3 before fusing completely with the nodal plexus. The next six bundles to form (laterals) establish some links with bundles from higher leaves in the node of entry, much more extensive connections in node n- 1, and fuse completely with the nodal plexus in node n-2. The next four lateral bundles to differentiate are more extensively linked in node n and fuse completely with the nodal plexus in node n - I . The remaining 16-20 bundles from the leaf (intermediates) follow much the same course but develop more extensive connections with other bundles. The extensive plexus which develops in each node ensures vascular connections between most bundles. The significance of these in transport is briefly discussed.

scholarly journals A role for spinal cord hypoxia in neurodegeneration

2019 ◽  
Vol 10 (11) ◽  
Author(s):  
Elena Hernandez-Gerez ◽  
Ian N. Fleming ◽  
Simon H. Parson
Keyword(s):  
Spinal Cord ◽  
Blood Flow ◽  
Traffic Accidents ◽  
Chronic Hypoxia ◽  
Road Traffic ◽  
Vascular System ◽  
Muscular Atrophy ◽  
Traumatic Event ◽  
Venous Occlusion ◽  
Tissue Response

Abstract The vascular system of the spinal cord is particularly complex and vulnerable. Damage to the main vessels or alterations to the regulation of blood flow will result in a reduction or temporary cessation of blood supply. The resulting tissue hypoxia may be brief: acute, or long lasting: chronic. Damage to the vascular system of the spinal cord will develop after a traumatic event or as a result of pathology. Traumatic events such as road traffic accidents, serious falls and surgical procedures, including aortic cross-clamping, will lead to an immediate cessation of perfusion, the result of which may not be evident for several days, but may have long-term consequences including neurodegeneration. Pathological events such as arterial sclerosis, venous occlusion and spinal cord compression will result in a progressive reduction of blood flow, leading to chronic hypoxia. While in some situations the initial pathology is exclusively vascular, recent research in neurodegenerative disease has drawn attention to concomitant vascular anomalies in disorders, including amyotrophic lateral sclerosis, spinal muscular atrophy and muscular sclerosis. Understanding the role of, and tissue response to, chronic hypoxia is particularly important in these cases, where inherent neural damage exacerbates the vulnerability of the nervous system to stressors including hypoxia.

Leaf Axil Anatomy of the Araucariaceae

1987 ◽  
Vol 35 (6) ◽  
pp. 631 ◽  
Author(s):  
GE Burrows
Keyword(s):  
Leaf Axil ◽  
Vascular Cylinder ◽  
Axillary Meristem ◽  
External Appearance ◽  
The Family ◽  
Vascular Connections

Well defined, persistent meristems, which possess neither a bud-like organisation nor vascular connections with the central vascular cylinder, were found in the apparently blank leaf axils of six species of Agathis and 13 species of Araucaria. In other conifers, leaf axils of similar external appearance are usually reported to lack, or gradually lose, any specialised bud-forming tissues. Meristems were found in all axils investigated and in this respect the Araucariaceae approach the typical angiospermous condition of a bud in each leaf axil. Evidence is presented that the type of axillary meristem ontogeny previously described for A. cunninghamii may be widespread in the family.

EFFECT OF UREA AND AMMONIUM NITRATE ON YIELDS AND NITROGEN CONCENTRATION OF TIMOTHY AND BROMEGRASS AND LOSS OF AMMONIA FROM UREA SURFACE APPLICATIONS

1987 ◽  
Vol 67 (1) ◽  
pp. 185-192 ◽  
Author(s):  
H. T. KUNELIUS ◽  
J. A. MACLEOD ◽  
K. B. MCRAE
Keyword(s):  
Ammonium Nitrate ◽  
Total Nitrogen ◽  
Dry Matter ◽  
Field Experiments ◽  
Nitrogen Concentration ◽  
Secondary Growth ◽  
Nitrogen Sources ◽  
Primary Growth ◽  
Total Nitrogen Concentration ◽  
Harvest Year

Urea and ammonium nitrate were applied at 30, 60, 90 and 120 kg N ha−1 in spring and after cutting the primary growth of timothy and bromegrass in three field experiments. Dry matter yields of timothy and bromegrass and total nitrogen concentration of tissue and nitrogen yields of timothy were determined. Loss of nitrogen as ammonia was monitored on microplots between the end of May and early July. Primary growth yields were usually similar for ammonium nitrate and urea but in the secondary growth timothy fertilized with ammonium nitrate outyielded timothy fertilized with urea in four out of six harvest years. Dry matter response to applied nitrogen was usually curvilinear in primary growth but linear in secondary growth over the nitrogen rates studied. Total nitrogen concentration in primary and secondary growths of timothy increased linearly with nitrogen rate during the initial 2–3 yr; ammonium nitrate and urea were equally effective in all but one harvest year. Total nitrogen production of timothy also increased linearly over the range of 30–120 kg N ha−1, while ammonium nitrate outyielded urea-fertilized timothy during one season in primary and two seasons out of four in secondary growth. Nitrogen losses increased from spring to summer, in general, with 68–75% of the variation explained by air temperature. Urea and ammonium nitrate were considered equivalent nitrogen sources for the primary growth of timothy but urea was less efficient in the secondary growth under summer conditions.Key words: Urea, ammonium nitrate, timothy, bromegrass, ammonia losses

scholarly journals From primary to secondary growth: origin and development of the vascular system

2007 ◽  
Vol 58 (13) ◽  
pp. 3485-3501 ◽  
Author(s):  
M. Baucher ◽  
M. El Jaziri ◽  
O. Vandeputte
Keyword(s):  
Vascular System ◽  
Secondary Growth
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