Xylary union between elongating lateral branches and the main stem in Populus deltoides

1983 ◽  
Vol 61 (4) ◽  
pp. 1040-1051 ◽  
Author(s):  
Philip R. Larson ◽  
David G. Fisher
Keyword(s):  
Populus Deltoides ◽  
Secondary Xylem ◽  
Cambial Activity ◽  
Main Axis ◽  
Main Stem ◽  
Leaf Trace ◽  
Primary Xylem ◽  
Lateral Bud ◽  
Lateral Branches ◽  
Secondary Vessels

The vasculature of elongating lateral branches was examined to determine how vessels produced in the branch unite with those produced in the main stem axis to form a continuous transport system. In a previous study it was found that differentiation of both primary and secondary xylem in a lateral bud or branch is independent of that in the main axis; i.e., xylem does not differentiate into the bud or branch from the main axis. When serial sections of the nodal region are followed downward, the bud vascular cylinder merges with that of the main axis and the adaxially situated bud traces (those nearest the stem) enter the bud gap margin first. The primary vessels of these bud traces differentiate in an oblique downward path along the margins of the bud gap, and they form radial files of primary vessels that lie adjacent to primary xylem of leaf traces in the stem. Traces situated more abaxially in the bud (those farther from the stem) contribute to other radial files of primary vessels, each of which lies progressively closer to the bud gap. Secondary xylem is initiated in the stem before it is in the branch. Consequently, the last-formed metaxylem vessels of the bud traces are continuous with secondary vessels of the stem. These latter vessels lie in the stem secondary xylem immediately external to primary xylem from the bud. Secondary xylem in the branch is initiated when foliage leaves and internodes mature. Secondary vessels formed in the branch traces are continuous with secondary vessels in the stem; these vessels are embedded in a matrix of fibers. Because cambial activity is more vigorous in the stem than in the branch, two vessels that are radially adjacent in the branch may be widely separated by fibers in the stem. The central trace of the axillant leaf enters the gap immediately below the last branch traces; at this level in the stem the leaf trace vasculature is entirely primary. The stem secondary xylem that overlies the leaf trace is continuous with that in the axillary branch.

Lateral branch vascularization: its circularity and its relation to anisophylly

1981 ◽  
Vol 59 (12) ◽  
pp. 2577-2591 ◽  
Author(s):  
Philip R. Larson ◽  
Jennifer H. Richards
Keyword(s):  
Populus Deltoides ◽  
Lateral Branch ◽  
Main Stem ◽  
Axillary Bud ◽  
The Third ◽  
Organizational Pattern ◽  
Lateral Branches ◽  
Bud Initiation ◽  
Derivatives Of ◽  
Lower Stem

The vasculature of elongating lateral branches of Populus deltoides Bartr. ex Marsh. was examined to determine how vascular continuity was attained around the entire branch circumference. In a previous study it was found that a pair of original bud traces (A, A′) gave rise to three pairs of bud traces in sequence (a, a′; b, b′; g, g′) that vascularized the axillary bud; the original bud traces then continued upward in the main stem axis. In this study we demonstrated that the lower, abaxial part of the branch cylinder was vascularized by derivatives of the first pair of bud traces (a, a′), the lateral parts primarily by derivatives of the second pair of bud traces (b, b′), and the upper, adaxial part by derivatives of the third pair of bud traces (g, g′). Thus, the organizational pattern for branch vascularization was established during the earliest stages of axillary-bud initiation. Leaves on all lateral branches were anisophyllous; the condition was related to the position of leaves in the phyllotactic array and to their vascularization. The smallest leaves always occurred on the upper branch side and their central traces were diverted upward in the main stem vascular cylinder. The largest leaves were usually on the lower stem side and their central traces were diverted downward. Some first-formed leaves were falcate, and the lateral traces serving the suppressed sides of their laminae were also found to be diverted upward in the main stem axis. It was suggested that both the small anisophyllous and the falcate leaves might result from a lower nutritional status because of their upward-directed leaf traces.

scholarly journals Apical control of xylem formation in the pine stem. I. Auxin effects and distribution of assimilates

2014 ◽  
Vol 51 (2) ◽  
pp. 187-201 ◽  
Author(s):  
Tomasz J. Wodzicki ◽  
Krzysztof Rakowski ◽  
Zofia Starck ◽  
Jarosław Porandowski ◽  
Stefan Zajączkowski
Keyword(s):  
Cell Wall ◽  
Late Summer ◽  
Cambial Activity ◽  
Early Summer ◽  
Main Stem ◽  
Wall Deposition ◽  
Daily Rate ◽  
Secondary Wall Deposition ◽  
Lateral Branches ◽  
Cell Wall Deposition

The effect of IAA upon cambial activity, xylem differentiation and translocation of assimilates from the lateral shoot was investigated in spring and late summer in decapitated and ring-barked young trees of <em>Pinus silvestris</em> in the forest stand. Decapitation interrupted cambial xylem production in the uppermost part of the main stem of decapitated trees in spring and late summer, regardless of whether lateral branches below were growing, dormant or disbudded, and the contact through phloem with the roots was maintained or severed. Auxin supplied to the decapitated stems caused an increasing stimulation of cambial xylem production in spring. It also stimulated cambial activity in August but was ineffective in September. Apical control of cambial xylem production was strongly dependent upon the continuity of phloem and/or cambial tissues of the decapitated main-stem-section with lower parts of the plant. Decapitation of the stem strongly reduced the daily rate of cell wall deposition in the cambial xylem derivatives which on the day the experiment started constituted the zones of radial enlargement and maturation. This reduction limited progressively secondary wall deposition in consecutive maturing tracheids even though the cells differentiated longer. Irrespective of the season, auxin prevented the effect of decapitation in cells which were already differentiating when the experiment started as well as extension of the maturation phase. The effect of auxin was somewhat reduced when the lateral branches were additionally decapitated in early summer. In early summer auxin caused a significant increase of the daily rate of cell wall deposition in cells of the cambial zone or the newly produced ones, thus resulting in formation of progressively thicker secondary walls. Late in summer assimilates were transported mostly to the lower part of the stem. Decapitation changed the intact tree pattern of assimilate distribution, increasing the transport in spring and reducing it later in the summer. Prevention of the contact with roots via phloem and cambium in spring (by ring-barking the stem at tree base) decreased decapitation-induced downward transport of assimilates. Application of auxin to the decapitated uppermost segment of the main stem resulted in a significant increase of assimilate translocation into the stem. At least two mechanisms of auxin involvement in regulation of the rate of secondary wall deposition in pine stem tracheids can be considered: (a) induction (or activation) of the cell wall metabolic potential which seems to occur during meristematic or early radial enlargement phases of tracheid differentiation, and (b) regulation of substrate availability during the phase of tracheid maturation.

Galtiera bostonensis, gen. et sp. nov., a protostelic calamopityacean from the New Albany shale of Kentucky

1987 ◽  
Vol 65 (2) ◽  
pp. 348-361 ◽  
Author(s):  
Charles B. Beck ◽  
William E. Stein Jr.
Keyword(s):  
Secondary Xylem ◽  
Vascular System ◽  
Pathological Response ◽  
Main Stem ◽  
Major Group ◽  
Infectious Agents ◽  
Primary Xylem ◽  
New Albany Shale ◽  
Stelar Morphology ◽  
Stem Fragment

Two parts of a single, anatomically preserved stem fragment form the basis of a new Lower Mississippian taxon that is characterized here in detail. Stelar morphology, leaf trace departure, secondary xylem, outer sparganum cortex, and Kalymma-like leaf bases provide evidence of taxonomic relationship with the Calamopityaceae. The primary vascular column is deeply three ribbed with protoxylem strands restricted to the periphery of the xylem. Trace departure is associated with a dextral shift in the position of primary xylem ribs such that the tip of each rib describes a helical course through the axis. The result is a Fibonacci phyllotactic fraction of at least 2/5. On the basis of our observations, we hypothesize that the protoxylem strands may comprise five sympodia and, further, that although protostelic in gross morphology, the primary vascular system of Galtiera might actually be more similar to typical eusteles of the Calamopityaceae than protosteles of any other major group. Sclerotic clusters and strands in the cortex are of interest because they are unusually numerous and are usually associated with the phloem either of the main stem vascular column or of leaf traces. The evidence is consistent with the hypothesis that this morphology reflects a pathological response by the plant to viral or other infectious agents.

scholarly journals Effect of auxin (iaa) upon the proteolytic system in differentiating secondary xylem of pine (Pinus sylvestris L.)

2014 ◽  
Vol 64 (1) ◽  
pp. 25-28 ◽  
Author(s):  
Krzysztof J. Rakowski ◽  
Tomasz J. Wodzicki
Keyword(s):  
Pinus Sylvestris ◽  
Proteolytic Activity ◽  
Secondary Xylem ◽  
Cambial Activity ◽  
Main Stem ◽  
Stem Segment ◽  
Proteolytic System ◽  
Simultaneous Application ◽  
Meristematic Activity

Effects of decapitation and IAA on proteolytic activity were studied in main stem of 4-7 year-old <i>Pinus sylvestris</i> trees. Proteolytic activity in the extract from differentiating secondary xylem was found to be totally reduced in decapitated 2-3 year-old segments of the main stem after a few weeks. Simultaneous application of IAA in lanolin paste prevented this reduction. Proteolytic activity reduced totally after decapitation was restored within 2 days when auxin was applied. Analogous responses to decapitated and auxin application were observed in respect to cambial activity and protein level. The latter effects were not correlated in time with the effects upon the activity of proteases. The differences were especially visible when phloem continuity between the decapited stem segment and the rest of the tree crown was broken by ring-barking. The results suggest dependence of a proteolytic system on the shoot apical control. In this epigenetic system of control the role of auxin seems to be directly associated with the seasonal meristematic activity of the cambium, which was observed in earlier studies.

scholarly journals RESILIENCE OF FERNS: WITH REFERENCE TO DESICCATION AND REHYDRATION STRESS OFFER NEW INSIGHTS

2017 ◽  
Vol 4 (2) ◽  
pp. 89-94
Author(s):  
Kavitha C.H ◽  
Meenu Krishnan ◽  
Murugan K
Keyword(s):  
Vascular Plants ◽  
Stress Proteins ◽  
Secondary Xylem ◽  
Plant Water Relations ◽  
Vascular Bundles ◽  
Late Cenozoic ◽  
Primary Xylem ◽  
Hydraulic Failure ◽  
Pit Membrane ◽  
Selection For

Ferns are one of the oldest vascular plants in existence and they are the second most diverse group of vascular plants followed to angiosperms. To unravel fern success has focused on the eco-physiological power and stress tolerance of their sporophyte and the gametophyte generations. In this context, those insightsencompass plant water relations, as well as the tolerance to and recovery from drought or desiccation stresses in the fern life cycle are reviewed. Lack of secondary xylem in ferns is compensated by selection for efficient primary xylem composed of large, closely arranged tracheids with permeable pit membranes.Protection from drought-induced hydraulic failure appears to arise from a combination of pit membrane traits and the arrangement of vascular bundles. Features such as tracheid-based xylem and variously sized megaphylls are shared between ferns and more derived lineages, and offer an opportunity to compare convergent and divergent hydraulic strategies critical to the success of xylem-bearing plants. Similarly the synthesis and accumulation of sugar, proline and stress proteins along with the production of pool of polyphenols add strength to desiccation stress. Thus, it can possible to suggest that selection acted on the physiology in a synchronous manner that is consistent with selection for drought tolerance in the epiphytic niche, and the increasingly diverse habitats of the mid to late Cenozoic.

SEPTORIA CANKER OF INTRODUCED AND NATIVE HYBRID POPLARS

1939 ◽  
Vol 17c (6) ◽  
pp. 195-204 ◽  
Author(s):  
J. E. Bier
Keyword(s):  
North American ◽  
Main Stem ◽  
Leaf Injury ◽  
Hybrid Poplars ◽  
Septoria Musiva ◽  
Lateral Branches

Studies have shown that Septoria musiva Peck, a North American fungus which occurs commonly as a leaf-spotting parasite on native poplars, produces cankers, in addition to leaf injury, on certain introduced poplars (Populus Rasumowskyana Schneid., P. Petrowskyana Schneid., and P. berolinensis Dipp.), and the native hybrids, Northwest and Saskatchewan poplar.Field observations and inoculation experiments demonstrated that most of the inoculum for spring infection arises from ascospores of a Mycosphaerella stage, and that the fungus enters the stems through mechanical wounds uninjured lenticels, leaf petioles, or stipules. Incipient cankers occur in the bark of the current year's wood, soon girdling leading and side shoots. They later spread from lateral branches into the main stem, developing into perennial cankers which ultimately girdle and kill the trees.

scholarly journals Influence of plant growth stage on resistance to anthracnose in Andean lupin (Lupinus mutabilis)

2015 ◽  
Vol 66 (7) ◽  
pp. 729 ◽  
Author(s):  
Cesar E. Falconi ◽  
Richard G. F. Visser ◽  
Sjaak van Heusden
Keyword(s):  
Developmental Stages ◽  
Main Stem ◽  
Colletotrichum Acutatum ◽  
Leaf Stage ◽  
Lupinus Mutabilis ◽  
Early Seedling ◽  
Flower Stage ◽  
Necrotic Spots ◽  
Lateral Branches ◽  
Plant Pathogen Interactions

Anthracnose, caused by Colletotrichum acutatum, is the most destructive fungal disease of Andean lupin (Lupinus mutabilis Sweet) in Ecuador and of other lupin species around the world. Symptoms of necrotic spots occur throughout the main stem, and infection progresses to cause bending of the main stem and lateral branches, resulting in yield loss. Although there is no known anthracnose resistance, this study aims to assess tolerance of Andean lupin and investigate lupin–C. acutatum interactions. Two Andean lupin genotypes, I-450 Andino and I-451 Guaranguito, were inoculated on the meristematic section of the main stem, either by spraying or by pipetting C. acutatum spores on to an artificial wound. Although the two methods gave similar results, spraying is the preferred method because it mimics natural pathogen infection. Plant-pathogen interactions were assessed at five different phenological stages (leaf stages 2–3, 4–5, 6–7, 8–9, and 10–11) with three C. acutatum isolates by using a 0–5 scale to assess disease symptoms. In both genotypes, anthracnose symptoms were greater at early seedling stage (2–3-leaf stage), decreasing significantly in early vegetative phase (6–7-leaf stage) and increasing again when the flower stage began (10–11-leaf stage). However, the tolerance of these two Andean lupin genotypes to anthracnose was not equally expressed at all developmental stages. We recommend, in a breeding program, that screening for anthracnose first occurs at the 6–7-leaf stage (6 weeks old) and again when flowering starts at the 10–11-leaf stage (10 weeks old) so that the overall tolerance can be determined. This method could be used in lupin breeding programs for improving resistance to anthracnose.

Arachnoxylon from the Middle Devonian of southwestern Virginia

1983 ◽  
Vol 61 (4) ◽  
pp. 1283-1299 ◽  
Author(s):  
William E. Stein Jr. ◽  
David C. Wight ◽  
Charles B. Beck
Keyword(s):  
Middle Devonian ◽  
Main Axis ◽  
Supplementary Information ◽  
Monotypic Genus ◽  
Primary Xylem ◽  
New Material ◽  
Shale Formation ◽  
Definition Of ◽  
A Minor ◽  
First Time

Eight specimens from the Middle Devonian Purcell Member of the Millboro Shale Formation in southwestern Virginia conform to a recent definition of the previously monotypic genus Arachnoxylon. The new material provides supplementary information on several tissue regions of the main axis, including evidence on variability in the structure of the protoxylem, and on departure of the large, or "major" traces. In addition, evidence is provided here for the first time on a discrete region, immediately adjacent to the primary xylem, containing probable conducting elements of the primary phloem, on the structure of the epidermis, and on the presence of multicellular superficial emergences. Although clearly assignable to Arachnoxylon, all but one of our specimens vary significantly from previous specimens in the genus in several features which may be interpreted as relating directly or indirectly to size. It is possible that all specimens in Arachnoxylon represent portions of a single kind of plant. However, organic connection between the large and small forms has not been demonstrated. We elect, therefore, to establish A. minor sp. n. for the smaller specimens.

scholarly journals WOOD ANATOMY OF THE VANGUERIEAE (IXOROIDEAERUBIACEAE), WITH SPECIAL EMPHASIS ON SOME GEOFRUTICES

IAWA Journal ◽  
2000 ◽  
Vol 21 (4) ◽  
pp. 443-455 ◽  
Author(s):  
Frederic Lens ◽  
Steven Jansen ◽  
Elmar Robbrecht ◽  
Erik Smets
Keyword(s):  
Pacific Ocean ◽  
Wood Anatomy ◽  
Secondary Xylem ◽  
Vessel Diameter ◽  
Underground Structures ◽  
Axial Parenchyma ◽  
Tropical Asia ◽  
Primary Xylem ◽  
The Pacific ◽  
The Pacific Ocean

The Vanguerieae is a tribe consisting of about 500 species ordered in 27 genera. Although this tribe is mainly represented in Africa and Madagascar, Vanguerieae also occur in tropical Asia, Australia, and the isles of the Pacific Ocean. This study gives a detailed wood anatomical description of 34 species of 15 genera based on LM and SEM observations. The secondary xylem is homogeneous throughout the tribe and fits well into the Ixoroideae s.l. on the basis of fibre-tracheids and diffuse to diffuse-in-aggregates axial parenchyma. The Vanguerieae include numerous geofrutices that are characterised by massive woody branched or unbranched underground parts and slightly ramified unbranched aboveground twigs. The underground structures of geofrutices are not homologous; a central pith is found in three species (Fadogia schmitzii, Pygmaeothamnus zeyheri and Tapiphyllum cinerascens var. laetum), while Fadogiella stigmatoloba shows central primary xylem which is characteristic of roots. Comparison of underground versus aboveground wood shows anatomical differences in vessel diameter and in the quantity of parenchyma and fibres.

Surgical studies on growth and xylem differentiation in the cotyledonary shoots of flax

1978 ◽  
Vol 56 (5) ◽  
pp. 476-482 ◽  
Author(s):  
M. V. S. Raju ◽  
W. N. Marchuk ◽  
Patricia L. Polowick
Keyword(s):  
Linum Usitatissimum ◽  
Secondary Xylem ◽  
Xylem Differentiation ◽  
Primary Xylem ◽  
The Third ◽  
Lateral Shoots

Growth and xylem differentiation in cotyledonary shoots were studied by partially isolating one shoot surgically in nondecapitated and decapitated flax plants (Linum usitatissimum var. noralta). Three types of cuts were made. The first type separated the shoot from the hypocotyl and the second from the epicotyl. The third type of cut was made at the node separating the two shoots, which, however, remained independently connected with the hypocotyl and epicotyl. In nondecapitated plants, the lateral shoots were inhibited. They had at their bases primary xylem strands, some of which were connected with the hypocotylary stele; the strands contained predominantly tracheids. In decapitated plants, the separated shoot grew vigorously when it was connected with both hypocotyl and epicotyl or hypocotyl alone. Such shoots contained at their bases abundant secondary xylem strands which were connected with the hypocotylary stele; the strands included predominantly vessels. The shoot that was isolated from the hypocotyl but connected with the epicotyl was inhibited even though it had abundant secondary xylem strands at its base. Results of this study suggest that growth of the cotyledonary shoot is dependent on the prior development of adequate xylem connections with the hypocotylary stele.

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