The mechanism of plication inception in palm leaves: histogenetic observations on the pinnate leaf of Chrysalidocarpus lutescens

1982 ◽  
Vol 60 (12) ◽  
pp. 2976-2998 ◽  
Author(s):  
Nancy G. Dengler ◽  
Ronald E. Dengler ◽  
Donald R. Kaplan
Keyword(s):  
Leaf Development ◽  
Leaf Primordia ◽  
Serial Sections ◽  
Ground Tissue ◽  
Differential Growth ◽  
Adaxial Side ◽  
Tissue Separation ◽  
Pinnate Leaf ◽  
Transmission Electron ◽  
Cell Layers

The reduplicate, pinnately compound leaf of Chrysalidocarpus lutescens begins development as a hood-shaped primordium with a smooth lamina. By the time the leaf is 5.5 mm in length, 40–42 pleats consisting of alternating ridges and furrows have been formed in a submarginal position on each half of the lamina. Serial sections of plastic-embedded leaf primordia were studied to distinguish between two alternative mechanisms of plication inception proposed in the literature: differential growth or tissue separation. Counts of the number of cell layers in the lamina during the period of plication initiation support the concept of differential growth, i.e., an increase in the number of tissue layers is observed at the site of furrow formation rather than a decrease in cell layers which would be expected if tissue separation were occurring. Ridges appear first on the adaxial side of the lamina, accompanied by periclinal and oblique divisions in the middle lamina layers. Further growth is associated with zones of anticlinal divisions alternating with the ridges. This plate meristem growth increases the surface area of a portion of the lamina bounded by the leaf apex, the unplicate margin, the petiole, and the rachis, and therefore tends to be accommodated by a buckling of the lamina between adaxial ridges. Intercalary growth of the intercostal sector causes the adaxial and abaxial ridges to be displaced from each other, deepening the plications. Examination of early stages of leaf development with the transmission electron microscope corroborates these results; there is no indication of schizogenous separation of cells within the ground tissue of the lamina or between protodermal cells. The protoderm and its cuticle are continuous at all stages of plication initiation, supporting the concept of differential growth.

Expression of shoot features in early leaf development of Murraya paniculata (Rutaceae)

1994 ◽  
Vol 72 (5) ◽  
pp. 678-687 ◽  
Author(s):  
Christian R. Lacroix ◽  
Rolf Sattler
Keyword(s):  
Early Development ◽  
Leaf Development ◽  
Sagittal Plane ◽  
Frontal Plane ◽  
Flowering Plants ◽  
Leaf Primordia ◽  
Differential Growth ◽  
Pinnate Leaf ◽  
Murraya Paniculata ◽  
Phylogenetic Perspective

The early development of the pinnately compound leaves in Murraya paniculata was studied using both epi-illumination and scanning electron microscopy as well as semithin plastic sectioning of the same specimens that were illustrated by means of epi-illumination. It is shown that morphological conclusions may be influenced by technical approaches such as the plane of sectioning. If the developing leaves are sectioned in the (median) sagittal plane, they appear to be rather different from stems and shoots. If, however, they are sectioned in the frontal plane, perpendicular to the sagittal plane, they appear more shoot-like in early development. Their apex could be described in terms of a tunica-corpus organization and the leaflet primordia are initiated like leaf primordia on a shoot tip with distichous phyllotaxy sensu lato. Subsequently, due to differential growth, reorientation of the leaflets occurs in one plane. Thus, the planar structure of the pinnate leaf is ontogenetically secondary. From a phylogenetic perspective, at least two conclusions are possible for plants with pinnate leaves such as those of Murraya: (i) if the ancestor of a pinnate taxon had simple leaves, the pinnate condition arose through homeosis, i.e., the expression of shoot features in leaf sites; (ii) if the ancestor of a pinnate taxon did not have simple leaves, the shoot-like early development of the pinnate leaves may indicate a common evolutionary basis of shoots and pinnate leaves in primitive branching systems. Since it is generally thought that the most primitive angiosperms have simple leaves, the homeotic hypothesis appears to be the preferred hypothesis for the origin of compound leaves in flowering plants. Key words: leaf development, comparative morphogenesis, shoot–leaf relationships, partial shoot theory of the leaf, homeosis.

Collenchyma in Panicum maximum (Poaceae): localisation and possible role

2003 ◽  
Vol 51 (1) ◽  
pp. 69 ◽  
Author(s):  
Elder A. S. Paiva ◽  
Sílvia R. Machado
Keyword(s):  
Electron Microscopy ◽  
Leaf Blade ◽  
Sudden Change ◽  
Panicum Maximum ◽  
Vascular Bundles ◽  
Serial Sections ◽  
Adaxial Side ◽  
Transition Area ◽  
Transmission Electron ◽  
Phases Of Development

This work relates the occurrence and distribution of collenchyma in Panicum maximum Jacq. P.�maximum leaves were collected at different phases of development and sampled from both the base of the sheath and from the sheath–leaf blade transition area. For the stems, the study was made by using hand-cut sections of the internodal base. In the leaves, analyses of serial sections showed, at the base and sheath–leaf blade transition area, a sudden change of tissue at vascular bundle. The vascular bundles are surrounded by sclerenchyma, both in the sheath and the leaf blade, as well as by fibrous threads that occur on the adaxial side of the central bundles. However, at the base of the sheath and at the sheath–leaf blade transition area, sclerenchyma was substituted for collenchyma. In the stem, the substitution of sclerenchyma associated with vascular bundles for collenchyma occurs at the base of the internode, in the pulvinus region. The analyses from transmission electron microscopy showed the presence of lamellated cell wall and active protoplast in collenchyma cells.

Three-Dimensional Reconstruction Using Stereo Pairs from Serial Thick Sections

1977 ◽  
Vol 35 ◽  
pp. 562-563
Author(s):  
Robert Glaeser ◽  
Thomas Bauer ◽  
David Grano
Keyword(s):  
Three Dimensional ◽  
Dimensional Structure ◽  
Serial Sections ◽  
Thin Sections ◽  
3 Dimensional ◽  
Transmission Electron ◽  
Freeze Dried ◽  
Dimensional Reconstruction ◽  
Stereo Imagery ◽  
Whole Mounts

In transmission electron microscopy, the 3-dimensional structure of an object is usually obtained in one of two ways. For objects which can be included in one specimen, as for example with elements included in freeze- dried whole mounts and examined with a high voltage microscope, stereo pairs can be obtained which exhibit the 3-D structure of the element. For objects which can not be included in one specimen, the 3-D shape is obtained by reconstruction from serial sections. However, without stereo imagery, only detail which remains constant within the thickness of the section can be used in the reconstruction; consequently, the choice is between a low resolution reconstruction using a few thick sections and a better resolution reconstruction using many thin sections, generally a tedious chore. This paper describes an approach to 3-D reconstruction which uses stereo images of serial thick sections to reconstruct an object including detail which changes within the depth of an individual thick section.

Fine structure of the kinetochores in six species of the Coleoptera

Genome ◽  
1997 ◽  
Vol 40 (3) ◽  
pp. 379-385
Author(s):  
Klaus Werner Wolf
Keyword(s):  
Direct Contact ◽  
Karyotype Evolution ◽  
Coccinella Septempunctata ◽  
Cell Types ◽  
Male Meiosis ◽  
Serial Sections ◽  
Cell Type ◽  
Present Survey ◽  
Transmission Electron ◽  
Size Variability

Kinetochore structure was examined in a total of 6 species from 5 different families of the Coleoptera using transmission electron microscopy of ultrathin serial sections. Metaphase spermatogonia and primary and secondary spermatocytes were studied in Tenebrio molitor (Tenebrionidae) to determine whether kinetochore structure varies depending on the cell type. In all three cell types, the kinetochore microtubules (MTs) were in direct contact with the chromosomal surface, and kinetochore plates were not detectable. In the other species, only metaphase I spermatocytes were examined. As in T. molitor, distinct kinetochore plates were also absent in Adelocera murina (Elateridae), Agapanthia villosoviridescens (Cerambycidae), and Coccinella septempunctata (Coccinellidae). However, bivalents in male meiosis of two representatives of the Chrysomelidae, Agelastica alni and Chrysolina graminis, showed roughly spherical kinetochores at their poleward surfaces. Microtubules were in contact with this material. Thus, although the present survey covers only a small number of species, it is clear that at least two kinetochore types occur in the Coleoptera. The cytological findings are discussed in the context of chromosome number and genome size variability in the Coleopteran families studied. It is suggested that properties of the kinetochores could play a role in karyotype evolution in the Coleoptera.Key words: bivalent, microtubule, meiosis, metaphase, spermatocyte.

Developmental comparison of leaf shape variation in three Chamaedorea species

Botany ◽  
2009 ◽  
Vol 87 (2) ◽  
pp. 210-221 ◽  
Author(s):  
Julia Nowak ◽  
Adam Nowak ◽  
Usher Posluszny
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Light Microscopy ◽  
Leaf Development ◽  
Leaf Shape ◽  
Shape Variation ◽  
Differential Growth ◽  
Scanning Electron ◽  
Palm Leaf ◽  
The Ideal

Compound palm leaf development is unique and consists of two processes. First, the primordial tissue folds through differential growth, forming plications. Second, these plications separate through an abscission-like process, forming leaflets. The second process of leaflet separation allows for the development of compound leaves. The question that this study addresses concerns the development of bifid leaves, as they do not form leaflets but only develop a cleft through an apical incision. The ideal genus to use for this study is Chamaedorea as it includes species with both pinnate and bifid leaves. Chamaedorea fragrans (Ruiz & Pav.) Mart. and Chamaedorea stolonifera H. Wendl. ex Hook. f. were chosen as the species with adult bifid leaves. Although Chamaedorea seifrizii Burret is a pinnate-leaved palm, its juvenile leaves are bifid. Scanning electron microscopy and light microscopy were used to study the development of bifid leaves. Our results indicate that neither of these bifid palms develop separation sites within the lamina, but rather the apical cleft develops through “late leaflet separation” or by an abscission-like process. In contrast, C. seifrizii juvenile leaves exhibit “early leaflet separation” when developing the apical cleft.

TEM and X-Ray Photoelectron Spectroscopic Studies of Wool Fibers after Cuticle Removal

1988 ◽  
Vol 58 (11) ◽  
pp. 640-645 ◽  
Author(s):  
Lyndsay M. Dowling ◽  
Leslie N. Jones ◽  
Ian H. Leaver ◽  
Anthony E. Hughes
Keyword(s):  
Electron Microscopy ◽  
Photoelectron Spectroscopy ◽  
Complete Removal ◽  
Spectroscopic Studies ◽  
Exposed Surface ◽  
X Ray ◽  
Immersion Medium ◽  
Wool Fibers ◽  
Transmission Electron ◽  
Cell Layers

A method is described for cleanly separating the cortex and cuticle of wool fibers using water or an aqueous buffered solution as the immersion medium. Nearly complete removal of cuticle cells can be achieved in 2–3 hours when snippets of wool are vortex-mixed with a suspension containing both glass fiber snippets and glass beads. Examination of treated fibers (transverse sections) by transmission electron microscopy indicates removal of cuticle cell layers (endo- and exocuticle), together with associated membrane intracellular bands ( i-layers). The surface elemental composition of the fiber (determined using x-ray photoelectron spectroscopy) changes appreciably with cuticle removal. The sulfur content of the intracellular cortical proteins at the exposed surface is estimated to be 2%, compared to 9% for the epicuticle proteins at the surface of untreated wool.

The Role of the Peripheral Cell Layers in the Geotropic Curvature of Sunflower Hypocotyls: a New Model of Shoot Geotropism

1977 ◽  
Vol 4 (3) ◽  
pp. 337 ◽  
Author(s):  
R Firn ◽  
J Digby
Keyword(s):  
Helianthus Annuus ◽  
Growth Regulator ◽  
Differential Rate ◽  
Lateral Movement ◽  
Differential Growth ◽  
Peripheral Cell ◽  
New Model ◽  
Helianthus Annuus L ◽  
Cell Layers

The rate of elongation of sunflower (Helianthus annuus L.) hypocotyl sections was found to be dependent on the rate of growth of the outermost cell layers (peripheral cell layers) of that tissue. Hypocotyl sections from which those layers had teen peeled grew but did not show typical geotropic curvature. A model of geotropic curvature is proposed where the differential growth causing curvature is due to a differential rate of elongation between the upper and lower peripheral cell layers of a horizontal shoot. In the model it is speculated that the peripheral cell layers are the site of both geoperception and georesponse. The model does not involve a lateral movement of a growth regulator and experiments with longitudinally bisected hypocotyl sections provided evidence consistent with this model but inconsistent with the Cholodny-Went theory of geotropism.

Samara development of black maple (Acer saccharum ssp. nigrum) with emphasis on the wing

1991 ◽  
Vol 69 (6) ◽  
pp. 1349-1360 ◽  
Author(s):  
Carol Jacobs Peck ◽  
Nels R. Lersten
Keyword(s):  
Acer Saccharum ◽  
Late Summer ◽  
Vascular Bundles ◽  
Short Fibers ◽  
Ground Tissue ◽  
Dorsal Ridge ◽  
Cell Layers ◽  
Oriented Parallel ◽  
Reticulate Venation ◽  
Lateral Orientation

Black maple (Acer saccharum Marsh, ssp. nigrum (Michx. f.) Desm.) carpels are initiated in late summer and over winter as paired, hood-shaped primordia with a naked megasporangium on each inrolled margin. The biloculate ovary develops from the lower portion of the primordium. The mature pericarp, about 30 cells thick, includes (i) the exocarp: outer epidermis and one to three layers of thick-walled hypodermal cells; (ii) the mesocarp: about 20 cells thick with reticulate venation and an innermost crystalliferous layer; and (iii) the endocarp: five to eight layers of short fibers oriented parallel to the locule surface. The samara wing arises from the dorsal ridge of the carpel primordium. The wing blade is approximately 10 cell layers thick with unifacial anatomy. Vascular bundles from opposite sides of the carpel alternate within the wing, thus xylem and phloem are oriented oppositely in adjacent bundles. The chlorenchymatous ground tissue ranges from compact subepidermal cells to elongated spongy cells, with increasing lateral orientation of cell arms in the mid-lamina. These central cells become sclerified, forming curved, branched fibers that buttress the vascular framework. Wing development and structure suggest early photosynthetic activity, which declines as sclerification and drying progress. Key words: Acer saccharum, anatomy, development, fruit, maple, samara.

Seed development, testa structure and precocious germination of Chinese cabbage (Brassica rapasubsp.pekinensis)

1998 ◽  
Vol 8 (3) ◽  
pp. 385-398 ◽  
Author(s):  
Chengwei Ren ◽  
J. Derek Bewley
Keyword(s):  
Seed Development ◽  
Chinese Cabbage ◽  
Dry Weight ◽  
Aleurone Layer ◽  
Palisade Layer ◽  
Adaxial Side ◽  
Precocious Germination ◽  
Mechanical Restraint ◽  
Cell Structures ◽  
Cell Layers

AbstractOn the basis of embryo and seed colour, morphology, accumulation of fresh and dry weight, seed development of Chinese cabbage (Brassica rapasubsp.pekinensis) can be divided into 10 discrete but contiguous stages. Precocious germination (PG) occurs in the seeds of a Chinese cabbage mutant on the parent plant mainly during the maturation period (from stage 5 to 8), with either the radicle or the cotyledon protruding out of the testa. All plants of the mutant line produce some PG seeds, but among the seeds, only 18% (maximum) germinate precociously. The developing mutant seeds have higher water contents and lower dry weights than those of the wild-type and are less tolerant of desiccation. The testa structure of Chinese cabbage seed is similar to that of otherBrassicaspecies. In developing seeds, it consists of the epidermis, subepidermis, palisade layer and pigmented layers, while in the mature dry seeds, all the cell layers except the palisade layer are crushed into non-cell structures and are stacked on the outer and inner faces of the palisade layer; the aleurone layer is fused to the testa. An alteration in testa structure of the mutant seeds (both non-germinated and precociously-germinated seeds) is probably related to PG. The secondary cell wall materials are less, or not deposited on the radial and basal walls of the palisade cells on the adaxial side of the testa, which could result in a weaker mechanical restraint, thus leading to PG.

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.

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