Axillary Meristem Ontogeny in Araucaria cunninghamii Aiton ex D Don

1986 ◽  
Vol 34 (4) ◽  
pp. 357 ◽  
Author(s):  
GE Burrows
Keyword(s):  
Vascular Cylinder ◽  
Axillary Meristem ◽  
Bud Formation ◽  
Undifferentiated State ◽  
Axillary Meristems ◽  
Typical Condition ◽  
Terminal Shoot ◽  
Araucaria Cunninghamii ◽  
Vascular Connections ◽  
Periderm Formation

The presence of axillary meristems in apparently blank leaf axils from the main stem of 2-year-old Araucaria cunninghamii is demonstrated. These meristems are groups of cells of meristematic appearance, which possess neither a bud-like organisation nor vascular or pro-vascular connections with the central vascular cylinder. They are first discernible in the axils of the recently initiated leaves, where each meristem is delimited from the vacuolating cortex by a shell zone. The axillary meristems then persist indefinitely in an inhibited, undifferentiated state, unless stimulated to bud formation by decapitation of the terminal shoot apex. They are exogenous in origin but are subsequently buried beneath the stem surface by the formation of localised periderms, the bark patches, and are not abscissed when extensive periderm formation begins. A. cunninghamii is apparently unique amongst conifers in possessing distinct, long-lived, exogenously initiated meristems or bud primordia in macroscopically blank leaf axils. The meristems are found in most leaf axils not occupied by branch buds. In this respect A. cunninghamii differs from most conifers and approaches the typical condition of angiosperms. The axillary meristems are inter- mediate in form between previously described vegetative axillary structures in gymnosperms and angiosperms.

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.

scholarly journals Establishment of a Rapid Plant Regeneration System in Physalis angulata L. through Axillary Meristems

2015 ◽  
Vol 7 (4) ◽  
pp. 471-474
Author(s):  
Owk ANIEL KUMAR ◽  
Songa RAMESH ◽  
Sape SUBBA TATA
Keyword(s):  
Shoot Culture ◽  
Shoot Multiplication ◽  
Multiple Shoot ◽  
Herbaceous Plant ◽  
Axillary Meristem ◽  
Regeneration System ◽  
Axillary Meristems ◽  
Meristem Explants ◽  
Physalis Angulata

An optimal plant propagation method of Physalis angulata L., a medicinally important herbaceous plant species has been developed using axillary meristem explants. Shoot bud proliferation was initiated from axillary meristem explants cultured on MS medium supplemented with various concentrations of 0.5-2.5mg/L/(BAP)/(Zeatin)/(KIN). The maximum in vitro response of shooting frequency of explants (88.1%) and shoots per explant (42) was achieved with medium containing 1.0mg/L BAP. Multiple shoot culture was established by repeated subculturing of the shoot buds of axillary meristems on shoot multiplication medium. Among the subculture media BAP in combination with 1.5mg/L (IAA)+0.25mg/L(GA3) produced maximum shoots per explant (128±0.29) after two weeks of culture. Effective in vitro shoot elongation and rooting was achieved on 1.0mg/L(GA3) and 1.0mg/L(IBA), respectively. Most of the generated shoots were successfully transferred to soil under field conditions. The survival percentage of the transferred plants on soil was found to be 90 per cent.  This protocol can be used for commercial propagation and for future genetic improvement studies.

Pathways for inflorescence and floral induction in Antirrhinum

Development ◽  
1996 ◽  
Vol 122 (5) ◽  
pp. 1535-1544 ◽  
Author(s):  
D. Bradley ◽  
C. Vincent ◽  
R. Carpenter ◽  
E. Coen
Keyword(s):  
Morphological Analysis ◽  
Floral Induction ◽  
Leaf Size ◽  
Axillary Meristem ◽  
The Third ◽  
Axillary Meristems ◽  
Meristem Identity ◽  
Short Internodes ◽  
Dependent Pathway ◽  
Subtending Leaves

The presentation of flowers on a modified stem, the inflorescence, requires the integration of several aspects of meristem behaviour. In Antirrhinum, the inflorescence can be distinguished by its flowers, hairy stem, modified leaves, short internodes and spiral phyllotaxy. We show, by a combination of physiological, genetical and morphological analysis, that the various aspects of the inflorescence are controlled by three pathways. The first pathway, depends on expression of the floricaula gene, and is rapidly and discretely induced by exposure to long daylength. Activation of this pathway occurs in very young axillary meristems, resulting in a floral identity. In addition, the length of subtending leaves and hairiness of the stem are partially modified. The second pathway affects leaf size, internode length, and stem hairiness, but does not confer floral meristem identity. This pathway is induced by long daylength, but not as rapidly or discretely as the floricaula-dependent pathway. The third pathway controls the switch in phyllotaxy from decussate to spiral and is activated independently of daylength. The coordination of these three programmes ensures that apical and axillary meristem behaviour is integrated.

A Scanning and Transmission Electron Microscope Study of Leaf Axil Structure in Araucaria cunninghamii

1991 ◽  
Vol 39 (1) ◽  
pp. 67 ◽  
Author(s):  
GE Burrows
Keyword(s):  
Smooth Endoplasmic Reticulum ◽  
Leaf Axil ◽  
Thin Walls ◽  
Hoop Pine ◽  
Axillary Meristems ◽  
Full Complement ◽  
Plasmodesmatal Frequency ◽  
Transmission Electron Microscope Study ◽  
Storage Products ◽  
Araucaria Cunninghamii

The cells of active plant meristems are characterised by their small size, thin walls and a full complement of organelles, most noticeably a large nucleus surrounded by densely staining, little-vacuolated cytoplasm. The axillary meristems of Araucaria cunninghamii Aiton ex D. Don (hoop pine) possess a similar ultrastructure, even though they quickly assume a near complete, potentially permanent quiescence following their detachment from the flanks of the actively dividing apical meristem. However, they differ from metabolically active cells in that those organelles and structures associated with cytokinesis and cell wall formation are either absent (microtubules) or infrequent and in an apparently inactive state (smooth endoplasmic reticulum, non-vesiculating dictyosomes, nuclei with a low heterochromatin to euchromatin ratio). In addition, storage products (starch, lipid globules), usually not present in metabolically active cells, are well developed. In addition to not developing a bud-like organisation, the meristems are also unlike typical axillary buds in that they have no vascular or provascular connections with the axial vascular tissues and are bounded adaxially by a group of thick-walled cells. While these cells constitute a physical barrier around the axillary meristems, they are nucleated and possess numerous simple pits that have a high plasmodesmatal frequency. Thus it appears that the meristems are not physiologically isolated, but are in cytoplasmic continuity with the remainder of the plant.

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.

Morphology and development of the primary and accessory buds of Eucalyptus regnans

1972 ◽  
Vol 20 (2) ◽  
pp. 175 ◽  
Author(s):  
KW Cremer
Keyword(s):  
Axillary Meristem ◽  
Serial Sections ◽  
Meristematic Tissue ◽  
Eucalyptus Regnans ◽  
Apical Bud ◽  
Direct Observations ◽  
Continuous Sequence ◽  
Shoot System ◽  
Axillary Meristems ◽  
Thin Walled

The vegetative axillary buds of Eucalyptus regnans F. Muell. at various ages were studied by light microscopy in serial sections and by direct observations in the field and glasshouse. All buds (except the very first apical bud) originated from axillary meristems, i.e. from generative tissue which arose in the axils of primordial leaves and survived in a meristematic condition for many years. Each axillary meristem normally produced one emergent primary bud and then an indefinite sequence of concealed accessory buds. The extensive dynamic shoot-system condensed within a primary bud comprised secondary as well as tertiary axes and their respective appendages. All parts were present throughout the year in a continuous sequence of maturation which extended also to the expanding shoot. During winter, development appeared to be merely slowed down or suspended. Primary buds which did not grow into shoots were shed after only a few weeks. The accessory buds were formed in a uniserial descending series at the base of and abaxial to each primary axillary bud. The first of the accessory buds was initiated within the primary bud, and the second within the expanding shoot. The first accessory bud resembled young primary buds in structure, but subsequent accessory buds were less and less complex. Keeping pace with the cambium, the axillary meristem formed a radial trace of thick-walled parenchyma in the wood and accessory buds embedded in a strand of thin-walled parenchyma in the bark. The distal portions of the bud strand and the buds embedded in it were shed progressively with the decorticating bark. Each of the bud strands which traversed the bark of 20-year-old E. viminalis Labill. was found to contain six to 12 radial strips of meristematic tissue. When epicormic growth was stimulated, several of these strips produced files of separate, new, condensed shoots. Of the scores of shoots thus initiated throughout the length of the bud strand, up to 10 or 20 of the distal ones emerged from the bark and grew into epicormic shoots. The buds of 20 other eucalypt species were examined by dissecting microscope only. It appeared that their bud systems were essentially similar to that of E. regnans. The widened concept of the axillary meristem shifts attention from individual buds to the continuous generative powers of the axillary meristem and helps to explain the outstanding capacity of the eucalypts to produce new shoots.

scholarly journals A suppressor of axillary meristem maturation promotes longevity in flowering plants

2020 ◽  
Author(s):  
Omid Karami ◽  
Arezoo Rahimi ◽  
Majid Khan ◽  
Marian Bemer ◽  
Rashmi R. Hazarika ◽  
...  
Keyword(s):  
Stem Cell ◽  
Embryonic Development ◽  
Ectopic Expression ◽  
Flowering Plants ◽  
Axillary Meristem ◽  
Flowering Genes ◽  
Axillary Meristems ◽  
Maturation State ◽  
Stem Cell Niches ◽  
Ga Biosynthesis

AbstractPost embryonic development and growth of flowering plants are for a large part determined by the activity and maturation state of stem cell niches formed in the axils of leaves, the so-called axillary meristems (AMs)1,2. Here we identify a new role for the Arabidopsis AT-HOOK MOTIF CONTAINING NUCLEAR LOCALIZED 15 (AHL15) gene as a suppressor of AM maturation. Loss of AHL15 function accelerates AM maturation, whereas ectopic expression of AHL15 suppresses AM maturation and promotes longevity in Arabidopsis and tobacco. Together our results indicate that AHL15 expression acts as a key molecular switch, directly downstream of flowering genes (SOC1, FUL) and upstream of GA biosynthesis, in extending the plant’s lifespan by suppressing AM maturation.

barren inflorescence2 regulates axillary meristem development in the maize inflorescence

Development ◽  
2001 ◽  
Vol 128 (15) ◽  
pp. 2881-2891 ◽  
Author(s):  
Paula McSteen ◽  
Sarah Hake
Keyword(s):  
Critical Role ◽  
Leaf Primordia ◽  
Axillary Meristem ◽  
Meristematic Tissue ◽  
Inflorescence Development ◽  
Stage Of Development ◽  
Sequence Of Events ◽  
Normal Maize ◽  
Meristem Development ◽  
Axillary Meristems

Organogenesis in plants is controlled by meristems. Shoot apical meristems form at the apex of the plant and produce leaf primordia on their flanks. Axillary meristems, which form in the axils of leaf primordia, give rise to branches and flowers and therefore play a critical role in plant architecture and reproduction. To understand how axillary meristems are initiated and maintained, we characterized the barren inflorescence2 mutant, which affects axillary meristems in the maize inflorescence. Scanning electron microscopy, histology and RNA in situ hybridization using knotted1 as a marker for meristematic tissue show that barren inflorescence2 mutants make fewer branches owing to a defect in branch meristem initiation. The construction of the double mutant between barren inflorescence2 and tasselsheath reveals that the function of barren inflorescence2 is specific to the formation of branch meristems rather than bract leaf primordia. Normal maize inflorescences sequentially produce three types of axillary meristem: branch meristem, spikelet meristem and floral meristem. Introgression of the barren inflorescence2 mutant into genetic backgrounds in which the phenotype was weaker illustrates additional roles of barren inflorescence2 in these axillary meristems. Branch, spikelet and floral meristems that form in these lines are defective, resulting in the production of fewer floral structures. Because the defects involve the number of organs produced at each stage of development, we conclude that barren inflorescence2 is required for maintenance of all types of axillary meristem in the inflorescence. This defect allows us to infer the sequence of events that takes place during maize inflorescence development. Furthermore, the defect in branch meristem formation provides insight into the role of knotted1 and barren inflorescence2 in axillary meristem initiation.

Striped maple: shoot growth and bud formation related to light intensity

1977 ◽  
Vol 7 (1) ◽  
pp. 1-7 ◽  
Author(s):  
B. F. Wilson ◽  
B. C. Fischer
Keyword(s):  
Solar Radiation ◽  
Light Intensity ◽  
Shoot Growth ◽  
Late Summer ◽  
Maximum Height ◽  
Forest Trees ◽  
Leaf Production ◽  
Bud Formation ◽  
Terminal Shoot ◽  
Light Maximum

Terminal shoot growth and bud formation in striped maple (Acerpensylvanicum) were followed both in vigorous and suppressed forest trees and in suppressed trees grown in the greenhouse and garden under 10 light intensities from 6 to 82% of solar radiation in the open. All buds contained (1) a pair of preformed early leaves that grew rapidly and (2) a pair of rudimentary primordia that became either bud scales in suppressed trees, after abortion of the blade, or a second pair of leaves in vigorous or released trees. The fate of the rudimentary primordia could be regulated by light intensity. They formed bud scales at 6% light or leaves at about 18% light. Maximum height growth and leaf pair formation occurred at 30–60% solar radiation in the open, although the first internode was longest under the lowest light. When leaf production stopped, bud formation was similar in vigorous and suppressed trees. The inner and outer bud scales and the pair of preformed early leaves were produced at 2- to 4-week intervals. The rudimentary primordia were not formed until after an interval of 8–12 weeks, in late summer near the end of bud formation.

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