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.

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.

scholarly journals Physical constraints on early blastomere packings

2021 ◽  
Vol 17 (1) ◽  
pp. e1007994
Author(s):  
James Giammona ◽  
Otger Campàs
Keyword(s):  
Cell Division ◽  
Developmental Stages ◽  
Physical Parameters ◽  
Cell Stage ◽  
Physical Constraints ◽  
Equilibrium Dynamics ◽  
Deformable Particles ◽  
Early Embryos ◽  
Early Developmental Stages ◽  
Early Developmental

At very early embryonic stages, when embryos are composed of just a few cells, establishing the correct packing arrangements (contacts) between cells is essential for the proper development of the organism. As early as the 4-cell stage, the observed cellular packings in different species are distinct and, in many cases, differ from the equilibrium packings expected for simple adherent and deformable particles. It is unclear what are the specific roles that different physical parameters, such as the forces between blastomeres, their division times, orientation of cell division and embryonic confinement, play in the control of these packing configurations. Here we simulate the non-equilibrium dynamics of cells in early embryos and systematically study how these different parameters affect embryonic packings at the 4-cell stage. In the absence of embryo confinement, we find that cellular packings are not robust, with multiple packing configurations simultaneously possible and very sensitive to parameter changes. Our results indicate that the geometry of the embryo confinement determines the packing configurations at the 4-cell stage, removing degeneracy in the possible packing configurations and overriding division rules in most cases. Overall, these results indicate that physical confinement of the embryo is essential to robustly specify proper cellular arrangements at very early developmental stages.

Leaf development in the anisophyllous shoots of Pellionia daveauana (Urticaceae)

1984 ◽  
Vol 62 (6) ◽  
pp. 1158-1170 ◽  
Author(s):  
Petra A. Mueller ◽  
Nancy G. Dengler
Keyword(s):  
Cell Division ◽  
Developmental Stage ◽  
Leaf Blade ◽  
Vascular System ◽  
Structural Features ◽  
Leaf Primordium ◽  
Early Developmental Stage ◽  
Time Period ◽  
Cell Dimensions ◽  
Early Developmental

The dorsiventral shoot system of Pellionia daveauana (Godefr.) N.E. Br. is characterized by opposite pairs of dimorphic leaves. The small dorsal leaves differ from the large ventral leaves by having a reduced leaf blade, fewer tissue layers in the epidermis and mesophyll, a reduced vascular system and significantly smaller cell size in all tissue layers. The observations reported here document the developmental basis of these morphological and histological differences. Although both dorsal and ventral leaves appear to be initiated simultaneously, the volume of the ventral leaf primordium is greater than that of the dorsal leaf primordium and growth in length occurs over a longer time period. Early plate meristem activity results in the elaboration of the ventral leaf blade, while plate meristem activity is lacking in dorsal leaves. During ventral leaf expansion periclinal divisions in adaxial and abaxial protoderm and ground meristem give rise to multiple epidermis and new mesophyll layers, respectively. Similar periclinal divisions in dorsal leaves occur at an earlier developmental stage and are restricted in extent. Measurements of cell dimensions show that cell enlargement also ceases at an early developmental stage in dorsal leaves. Development of the ventral leaf is characterized by a relatively long period of cell division and enlargement. In contrast, early cessation of cell division and precocious cell maturation result in the distinctive structural features of the dorsal leaf blade.

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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