Structure and development of terminal bud scales in green ash

1990 ◽  
Vol 68 (1) ◽  
pp. 12-20 ◽  
Author(s):  
E. K. Merrill
Keyword(s):  
Developmental Stages ◽  
Early Summer ◽  
Leaf Primordia ◽  
Apical Region ◽  
Fraxinus Pennsylvanica ◽  
Green Ash ◽  
Foliage Leaf ◽  
Terminal Bud ◽  
Terminal Buds ◽  
Early Developmental

Structure and development of terminal bud scales of green ash (Fraxinus pennsylvanica var. subintegerrima) were studied to provide a basis for comparison with foliage leaves of the same species. To identify early developmental stages of bud scales, structure and phenology of terminal buds were investigated first. Overwintering terminal buds have typically three or four pairs of bud scales and three to six pairs of foliage leaf primordia. Bud scales have a flattened base topped by rudimentary leaflets. After bud break, the first leaf primordia that are initiated develop and mature into terminal bud scales by early summer. Although morphology and anatomy of mature foliage leaves and bud scales are very different, primordia of leaf forms are similar until they reach a length of 500 μm. At that length both leaf forms have a base and apical leaflets. Bud scale bases widen and elongate without much thickening, while growth in the apical region is restricted. Marginal growth of the bud scale base is different from that described for most leaf blades. Terminal bud scales could be interpreted as being ontogenetically derived from foliage leaf primordia.

Heteroblastic seedlings of green ash. III. Cell division activity and marginal meristems

1986 ◽  
Vol 64 (11) ◽  
pp. 2662-2668 ◽  
Author(s):  
E. K. Merrill
Keyword(s):  
Cell Division ◽  
Leaf Blade ◽  
Developmental Stages ◽  
Leaf Primordia ◽  
Leaf Margin ◽  
Green Ash ◽  
Histological Differentiation ◽  
Cell Counts ◽  
Histological Criteria ◽  
Early Developmental

The early developmental stages of simple and compound leaves of green ash (50–400 μm long) were used to relate cell division activity (mitotic index) to developing leaf form and histological differentiation. Densely cytoplasmic cells within cross-sectioned leaf primordia have higher mitotic indices than protodermal cells and other internal cells that are more vacuolate. Among densely cytoplasmic cells mitotic indices decrease from the primordial leaf margin toward the procambium. Ground meristem cells within three to five cell widths of the primordial margin had the highest mitotic indices. Actual cell counts indicate that densely cytoplasmic cells increase in number in areas of leaf blade or leaflet initiation more than do vacuolate cells or protodermal cells. It is proposed that marginal meristems defined by spatial and histological criteria are important in producing new cells that are the basis for the generation of simple and compound leaf forms.

Shoot ontogeny in Fraxinus pennsylvanica (green ash). I. Seasonal cycle of terminal meristem activity

1989 ◽  
Vol 67 (6) ◽  
pp. 1624-1632 ◽  
Author(s):  
W. R. Remphrey
Keyword(s):  
Seasonal Cycle ◽  
Histological Analysis ◽  
Leaf Primordia ◽  
Leaf Primordium ◽  
Fraxinus Pennsylvanica ◽  
Green Ash ◽  
Heat Unit ◽  
Foliage Leaf ◽  
Axillary Meristems ◽  
Bud Initiation

Terminal meristem ontogeny of mature Fraxinus pennsylvanica var. subintegerrima (Vahl) Fern, (green ash) was investigated by bud dissection, histological analysis, and scanning electron microscopy. The shoots were completely preformed and bud-scale initiation for the next bud began in the spring shortly before any visible sign of swell. Foliage-leaf initiation began in May and ceased in late June or early July, but there were certain differences in primordium production patterns between the two trees investigated and between the years of the study. Although temperature, as measured by heat-unit accumulation, played a significant role in the onset of shoot expansion and primordium initiation, its importance in controlling these processes diminished as the season progressed. Buds formed in the axil of every leaf primordium, but those in the axils of scales remained small. There was evidence of axillary bud initiation as early as the P1, stage. By P2 or P3 there was a clearly discernable shell zone of elongated cells. Such cells had relatively large vacuoles concentrated at each end, in contrast with the essentially nonvacuolate cells of the incipient bud meristem. In the terminal resting bud, there were well-developed scale-axil buds and protruding axillary meristems associated with foliage-leaf primordia.

Heteroblastic seedlings of green ash. I. Predictability of leaf form and primordial length

1986 ◽  
Vol 64 (11) ◽  
pp. 2645-2649 ◽  
Author(s):  
E. K. Merrill
Keyword(s):  
Leaf Development ◽  
Leaf Growth ◽  
Leaf Primordia ◽  
Fraxinus Pennsylvanica ◽  
Green Ash ◽  
Leaf Form ◽  
Compound Leaf ◽  
Controlled Conditions ◽  
Plastochron Index

Green ash (Fraxinus pennsylvanica var. subintegerrima) seedlings are heteroblastic; during development they produce two types of leaves, simple and compound. When grown under controlled conditions, the sequence of leaf types is predictable. Simple leaves are always at the first four nodes; compound leaves are always at node 8 and above. Nodes 5 through 7 have progressively fewer simple leaves and more compound leaves. Leaf growth on seedlings meets the preconditions of the plastochron index and leaf plastochron index. These indices, as well as the length of single expanding leaves, can be used to predict lengths of leaf primordia at nodes 4 and 8 so that early, simple and compound leaf development can be compared in further studies of green ash.

Shoot ontogeny in Arctostaphylos uva-ursi (bearberry): the annual cycle of apical activity

1984 ◽  
Vol 62 (9) ◽  
pp. 1925-1932 ◽  
Author(s):  
W. R. Remphrey ◽  
T. A. Steeves
Keyword(s):  
Leaf Primordia ◽  
Growth Strategy ◽  
Bud Burst ◽  
Foliage Leaf ◽  
Lateral Buds ◽  
Previous Season ◽  
Lateral Shoots ◽  
Terminal Buds ◽  
Floral Bracts ◽  
Vegetative Bud

Phenological investigation of shoot ontogeny in the prostrate shrub Arctostaphylos uva-ursi (L.) Spreng. (bearberry) at two sites in Saskatchewan, Canada, revealed that most growth occurred from May to July. Vegetative bud swell and leaf primordium initiation began around the 1st of May. Following bud burst in late May, elongation of most shoots continued for 3 to 5 weeks. Most bearberry shoots were not completely preformed; that is, several neoformed foliage leaves were initiated during current-year shoot extension in addition to the leaves that had been preformed during the previous season and had overwintered in the bud. In many shoots, a terminal inflorescence was initiated in the latter part of May of the year prior to anthesis. During conversion to the flowering state, the terminal apex initiated seven to nine floral bracts, each subtending a bud. In vegetative terminal shoots, bud-scale initiation also began in mid-May to late May and new terminal buds were first evident in early to mid-June. Following the initiation of bud scales and transitional leaves, the production of preformed foliage-leaf primordia continued until about August 1. Protruding lateral buds were evident histologically in the axils of preformed leaves during the initial stages of bud swell. On long, dominant shoots numerous neoformed leaves were initiated and shoot extension was often prolonged well into August. Second-flush terminal and lateral shoots, which resulted from the expansion of neoformed leaves and internodes, were also observed. The occurrence of neoformed growth in a large proportion of shoots suggests an exploitive, opportunistic growth strategy in this species.

Leader size and number of leaf primordia as factors in timing of terminal bud flush in black spruce and tamarack

1987 ◽  
Vol 17 (11) ◽  
pp. 1390-1393
Author(s):  
V. J. Lieffers
Keyword(s):  
Black Spruce ◽  
Leaf Primordia ◽  
North Central ◽  
Large Numbers ◽  
Terminal Bud ◽  
Final Length ◽  
Bud Growth ◽  
Terminal Buds ◽  
Individual Trees

Black spruce (Piceamariana (Mill.) B.S.P.) and tamarack (Larixlaricina (Du Roi) K. Koch) in a peatland in north central Alberta were examined twice weekly for terminal bud flush, length of leader, and cessation of leader elongation. Time of terminal bud flush of black spruce, which has determinate bud growth, was negatively correlated with the final length of leader. Differences in timing of flush of terminal buds of individual trees between 1984 and 1985 were negatively related to the ratio of leader length in 1984 to that in 1985. It is proposed that part of the variability in time of bud flush is related to the number of leaf primordia in the expanding bud. Buds with large numbers of leaf primordia flushed earlier than buds with few primordia. Time of terminal bud flush of tamarack, which has indeterminate bud growth, was poorly correlated with the final length of leader.

Correlated Studies of Cellular Interactions Using TEM, Freeze Etching, and SEM

1974 ◽  
Vol 32 ◽  
pp. 320-321
Author(s):  
J. P. Revel
Keyword(s):  
Developmental Stages ◽  
Three Dimensional ◽  
Cell Movement ◽  
Cellular Interactions ◽  
Serial Sections ◽  
Cell Sheets ◽  
Freeze Etching ◽  
Early Developmental

Movement of individual cells or of cell sheets and complex patterns of folding play a prominent role in the early developmental stages of the embryo. Our understanding of these processes is based on three- dimensional reconstructions laboriously prepared from serial sections, and from autoradiographic and other studies. Many concepts have also evolved from extrapolation of investigations of cell movement carried out in vitro. The scanning electron microscope now allows us to examine some of these events in situ. It is possible to prepare dissections of embryos and even of tissues of adult animals which reveal existing relationships between various structures more readily than used to be possible vithout an SEM.

Review of early developmental stages of trilobites and agnostids from the Barrandian area (Czech Republic)

2017 ◽  
Vol 186 (1) ◽  
pp. 103-112
Author(s):  
Lukáš Laibl ◽  
Oldřich Fatka
Keyword(s):  
Czech Republic ◽  
Developmental Stages ◽  
History Of Research ◽  
Early Developmental Stages ◽  
History Of ◽  
Barrandian Area ◽  
Early Developmental

This contribution briefly summarizes the history of research, modes of preservation and stratigraphic distribution of 51 trilobite and five agnostid taxa from the Barrandian area, for which the early developmental stages have been described.

scholarly journals The Effect of an Anthropogenic Magnetic Field on the Early Developmental Stages of Fishes—A Review

2021 ◽  
Vol 22 (3) ◽  
pp. 1210
Author(s):  
Krzysztof Formicki ◽  
Agata Korzelecka-Orkisz ◽  
Adam Tański
Keyword(s):  
Magnetic Fields ◽  
Developmental Stages ◽  
Negative Influence ◽  
Pigment Cells ◽  
Egg Activation ◽  
Industrial Equipment ◽  
Positive Effects ◽  
Early Developmental Stages ◽  
Species Specific ◽  
Early Developmental

The number of sources of anthropogenic magnetic and electromagnetic fields generated by various underwater facilities, industrial equipment, and transferring devices in aquatic environment is increasing. These have an effect on an array of fish life processes, but especially the early developmental stages. The magnitude of these effects depends on field strength and time of exposure and is species-specific. We review studies on the effect of magnetic fields on the course of embryogenesis, with special reference to survival, the size of the embryos, embryonic motor function, changes in pigment cells, respiration hatching, and directional reactions. We also describe the effect of magnetic fields on sperm motility and egg activation. Magnetic fields can exert positive effects, as in the case of the considerable extension of sperm capability of activation, or have a negative influence in the form of a disturbance in heart rate or developmental instability in inner ear organs.

scholarly journals Wnt/β-catenin Pathway-Mediated PPARδ Expression during Embryonic Development Differentiation and Disease

2021 ◽  
Vol 22 (4) ◽  
pp. 1854
Author(s):  
Tabinda Sidrat ◽  
Zia-Ur Rehman ◽  
Myeong-Don Joo ◽  
Kyeong-Lim Lee ◽  
Il-Keun Kong
Keyword(s):  
Embryonic Development ◽  
Transcriptional Activation ◽  
Target Gene ◽  
Developmental Stages ◽  
Embryonic Stem ◽  
Hereditary Diseases ◽  
Peroxisome Proliferator ◽  
Peroxisome Proliferator Activated Receptor ◽  
Stem Cell Regulation ◽  
Early Developmental

The Wnt/β-catenin signaling pathway plays a crucial role in early embryonic development. Wnt/β-catenin signaling is a major regulator of cell proliferation and keeps embryonic stem cells (ESCs) in the pluripotent state. Dysregulation of Wnt signaling in the early developmental stages causes several hereditary diseases that lead to embryonic abnormalities. Several other signaling molecules are directly or indirectly activated in response to Wnt/β-catenin stimulation. The crosstalk of these signaling factors either synergizes or opposes the transcriptional activation of β-catenin/Tcf4-mediated target gene expression. Recently, the crosstalk between the peroxisome proliferator-activated receptor delta (PPARδ), which belongs to the steroid superfamily, and Wnt/β-catenin signaling has been reported to take place during several aspects of embryonic development. However, numerous questions need to be answered regarding the function and regulation of PPARδ in coordination with the Wnt/β-catenin pathway. Here, we have summarized the functional activation of the PPARδ in co-ordination with the Wnt/β-catenin pathway during the regulation of several aspects of embryonic development, stem cell regulation and maintenance, as well as during the progression of several metabolic disorders.

scholarly journals Mitochondrial Processes during Early Development of Dictyostelium discoideum: From Bioenergetic to Proteomic Studies

Genes ◽  
2021 ◽  
Vol 12 (5) ◽  
pp. 638
Author(s):  
Monika Mazur ◽  
Daria Wojciechowska ◽  
Ewa Sitkiewicz ◽  
Agata Malinowska ◽  
Bianka Świderska ◽  
...  
Keyword(s):  
Life Cycle ◽  
Developmental Stages ◽  
Coupling Efficiency ◽  
Slime Mold ◽  
Intact Cells ◽  
Life Cycle Stages ◽  
Early Developmental Stages ◽  
Proteomic Study ◽  
And Function ◽  
Early Developmental

The slime mold Dictyostelium discoideum’s life cycle includes different unicellular and multicellular stages that provide a convenient model for research concerning intracellular and intercellular mechanisms influencing mitochondria’s structure and function. We aim to determine the differences between the mitochondria isolated from the slime mold regarding its early developmental stages induced by starvation, namely the unicellular (U), aggregation (A) and streams (S) stages, at the bioenergetic and proteome levels. We measured the oxygen consumption of intact cells using the Clarke electrode and observed a distinct decrease in mitochondrial coupling capacity for stage S cells and a decrease in mitochondrial coupling efficiency for stage A and S cells. We also found changes in spare respiratory capacity. We performed a wide comparative proteomic study. During the transition from the unicellular stage to the multicellular stage, important proteomic differences occurred in stages A and S relating to the proteins of the main mitochondrial functional groups, showing characteristic tendencies that could be associated with their ongoing adaptation to starvation following cell reprogramming during the switch to gluconeogenesis. We suggest that the main mitochondrial processes are downregulated during the early developmental stages, although this needs to be verified by extending analogous studies to the next slime mold life cycle stages.

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