scholarly journals The sequence of cell divisions in the I tunic layer of Actinidia arguta Planch in light of the development of twin cell complexes

2014 ◽  
Vol 55 (2) ◽  
pp. 171-179 ◽  
Author(s):  
Zofia Puławska
Keyword(s):  
Leaf Primordia ◽  
Cell Complexes ◽  
Actinidia Arguta ◽  
Cell Divisions ◽  
Meristematic Activity ◽  
Mother Cells

In <em>Actinidia arguta</em>, the I tunc layer is formed by four cell complexes which descend from single initials. These initials are positioned in a corner of their complex, around the meristem axis. The meristematic activity of the I tunic layer depends on the formative divisions of the initials; the entire I tunic layer above the youngest leaf primordia is formed during the time the initials undergo only 4-8 divisions. In light of the development of the twin cell complexes. it is impossible for cells to be displaced from the I tunic layer into the meristem. The supposition is set forth that the impermanent. mericlinal sectors on variegated perinclinal chimeras develop due to periclinal cleavages within the subcomplexes which derive from tissue mother cells. Whereas. the cell initials do not undergo periclinal divisions and are not displaced.

scholarly journals Rape embryogenesis. IV. Appearance and disappearance of starch during embryo development

2014 ◽  
Vol 51 (3-4) ◽  
pp. 381-387 ◽  
Author(s):  
Teresa Tykarska
Keyword(s):  
Apical Part ◽  
Embryo Axis ◽  
Starch Grains ◽  
Cell Divisions ◽  
Embryo Cells ◽  
Dividing Cells ◽  
Gradual Accumulation ◽  
Black Seeds ◽  
Mother Cells ◽  
Storage Starch

Starch appears first in the suspensor of the proembryo with two-cell apical part. It is observed in the embryo proper from the octant stage. At first it is visible in all the embryo cells in the form of minute transient grains which disappear during cell divisions. But the columella mother cells and their derivatives have persistent large grains. When the embryo turns green in the heart stage a gradual accumulation of storage starch begins and lasts to the end of embryogenesis. Storage starch grains appear first in the auter cortex layers of the hypocotyl where the largest grains are to be found later, and afterwards in all the other tissues. Starch is usually absent in the frequently dividing cells, but even there it appears in the form of minute grains after the end of cell divisions. Disappearance of starch starts when the intensive green colour of the seed coat begins to fade. The first to disappear are the smallest granules in the regions where they were noted latest. In the embryo axis the starch grains remain deposited longest in dermatogen and cortex cells in the lower hypocotyl part. They are visible there, still when the seed turns brown. In black seeds starch may be only found in the columella the cells of which throughout embryogenesis contain amyloplasts filled with starch. These grains disappear completely at the time when the seeds become dry.

Bud development in Picea engelmannii. I. Vegetative bud development, differentiation, and early development of reproductive buds

1983 ◽  
Vol 61 (9) ◽  
pp. 2291-2301 ◽  
Author(s):  
Derek L. S. Harrison ◽  
John N. Owens
Keyword(s):  
Shoot Elongation ◽  
Longitudinal Axis ◽  
Leaf Primordia ◽  
Axillary Buds ◽  
Picea Engelmannii ◽  
Bud Burst ◽  
Bud Development ◽  
Vegetative Buds ◽  
Terminal Buds ◽  
Mother Cells

Vegetative buds of Engelmann spruce (Picea engelmannii Parry) from the Prince George Forest District (British Columbia) were collected and studied. In mid-April, dormancy ended as determined from mitotic divisions within the leaf primordia; 2 weeks later mitotic activity occurred in the bud apices. Bud-scale initiation began in terminal buds by late May followed by that in axillary buds 2 weeks later. Shoot elongation began in late May, bud burst occurred in late June, and both shoot elongation and bud-scale initiation were complete by late July. Terminal buds began to differentiate by the initiation of leaf primordia, into vegetative buds early in August whereas axillary buds began to differentiate 1 week later. Leaf initiation was completed in all vegetative buds by late September and buds were dormant by mid-October. Pollen cones initiated microsporophylls after bud-scale initiation. Microsporangial initiation began in late August. Microsporangial enlargement began in mid-September and continued until dormancy when pollen mother cells were observed in a premeiotic stage. Seed cones initiated bracts directly after bud-scale initiation. In mid-August, ovuliferous scales began to be initiated. Two ovule primordia formed adaxially, one on each side of the median longitudinal axis of each ovuliferous scale. Each ovule formed one large central megaspore mother cell which overwintered in a premeiotic stage.

scholarly journals An illustrated step-by-step protocol for investigating liverwort chromosomes

2021 ◽  
Vol 43 (1) ◽  
Author(s):  
ARETUZA SOUSA ◽  
SUSANNE S. RENNER
Keyword(s):  
Acetic Acid ◽  
Developmental Stage ◽  
Vascular Plants ◽  
Glacial Acetic Acid ◽  
Mitotic Chromosome ◽  
Cell Divisions ◽  
Cytogenetic Studies ◽  
The Right ◽  
Mother Cells ◽  
Young Sporophytes

Cytogenetic studies in bryophytes have been limited by the difficulty of obtaining sufficient dividing nuclei and by the absence of modern protocols. The technical difficulties stem from the plants’ small size and lack of roots and pollen mother cells, the main sources of cells in division in vascular plants. In bryophytes instead, tiny sporophytes, antheridia, or phyllid meristems must be used to obtain meiotic or mitotic chromosome spreads. We here describe the preparation of such spreads from phyllids, antheridia, and sporophytes in several species of liverworts and compare available protocols with or without prefixation treatments. We also provide illustrated step-by-step instructions. The three prefixation agents (including colchicine) that we tested failed to improve synchronization of cell divisions. Young sporophytes were the best source of diploid synchronized cells, while antheridia were the best source of haploid cells. For meiotic nuclei, a short fixation of capsule tissue at the right developmental stage with 45% acetic acid sufficed to conserve the DNA for cytological investigations, while for mitotic nuclei, fixation in 3:1 ethanol/glacial acetic acid for a longer period (4–24 h) worked well.

The initial protrusion of a leaf primordium can form without concurrent periclinal cell divisions

1971 ◽  
Vol 49 (9) ◽  
pp. 1601-1603 ◽  
Author(s):  
Donald E. Foard
Keyword(s):  
Gamma Rays ◽  
Shoot Apex ◽  
Cell Layer ◽  
Fold Increase ◽  
Leaf Primordia ◽  
Leaf Primordium ◽  
Initial Number ◽  
Wheat Grains ◽  
Cell Divisions ◽  
Number Of Cells

The view that periclinal cell divisions cause the initial protrusion of a leaf primordium may be tested by using ionizing radiation to prevent cell divisions without preventing growth. After receiving 800 krad of gamma rays, wheat grains containing embryos with three leaf primordia produce seedlings in which a fourth protrusion of the shoot apex forms unaccompanied by cell divisions. This protrusion without periclinal divisions occurs in the same phyllotactic position as that of the fourth leaf primordium in which periclinal divisions occur. In addition to proper phyllotactic position, the protrusion without cell divisions is formed by the outermost cell layer, as is the initial protrusion of a typical leaf primordium of wheat; moreover, the initial number of cells involved is the same in both kinds of protrusions. Therefore the fourth protrusion in seedlings from irradiated grain is interpreted as the initial protrusion of a leaf primordium that formed without periclinal cell divisions. Measured along the axis of greatest extension, the protrusions without cell divisions represent about a four- to eight-fold increase over the anticlinal dimension of the surface-cell layer in the embryo. These protrusions do not develop further. The absence of cell divisions limits the extent of primordial growth, but does not prevent its inception. Periclinal cell divisions do not cause the initial protrusion of a leaf primordium.

Differentiation of bud meristems and cataphylls during adventitious bud formation on embryos of Picea abies

1989 ◽  
Vol 67 (2) ◽  
pp. 422-428 ◽  
Author(s):  
Sara Von Arnold ◽  
Chris Hawes
Keyword(s):  
Picea Abies ◽  
Adventitious Bud ◽  
Bud Formation ◽  
Meristematic Cells ◽  
Cell Divisions ◽  
Adventitious Bud Formation ◽  
Cytokinin Treatment ◽  
Meristematic Activity ◽  
Xylem Elements ◽  
Needle Primordia

Embryos of Picea abies were pulse-treated with benzyladenine for 24 h and then cultured on medium lacking growth regulators. Meristemoids developed on all embryos during the 2nd week after the cytokinin treatment. Cells within the meristemoids divided randomly. As the meristemoids developed, further cell divisions became more organized so that separate regions of meristematic activity could be distinguished within each meristemoid. These meristematic regions developed into individual nodules and each nodule developed further into either a bud meristem or a cataphyll. Cataphylls were composed of unorganized, vacuolated, thick-walled cells whereas bud meristems were composed of organized meristematic cells. Later, xylem elements developed at the base, and needle primordia at the top of bud meristems. The bud apex had cytohistological zonation typical of conifers. The appearance of the developing adventitious buds depended on the number of cataphylls formed per bud as well as on the marginal expansion of the cataphylls.

Abnormal cell divisions in leaf primordia caused by the expression of the rice homeobox gene

1996 ◽  
Vol 251 (1) ◽  
pp. 13 ◽  
Author(s):  
Yutaka Sato ◽  
Masanori Tamaoki ◽  
Taka Murakami ◽  
Naoki Yamamoto ◽  
Yuriko Kano-Murakami ◽  
...  
Keyword(s):  
Homeobox Gene ◽  
Leaf Primordia ◽  
Abnormal Cell ◽  
Cell Divisions

Cytological and histological changes induced by cold temperature in the young shoots of Marquillo × Kenya Farmer wheat dwarf 1

1972 ◽  
Vol 50 (3) ◽  
pp. 403-408 ◽  
Author(s):  
J. D. Mahon ◽  
D. T. Canvin
Keyword(s):  
Apical Meristem ◽  
Leaf Primordia ◽  
Vascular Bundles ◽  
Vascular Differentiation ◽  
Main Shoot ◽  
Histological Changes ◽  
Whole Plant ◽  
Meristematic Activity ◽  
Extensive Cell ◽  
Extent Of Damage

The growth of Marquillo × Kenya Farmer 1 heat plants has been shown to be irreversibly terminated if they are exposed to a 16° temperature when 10 days old and it has been proposed that this low temperature sensitivity proceeds through a rapid inactivation of the shoot apical meristem. Histological and microautoradiographic techniques were used to study the effects of 16° treatment on the morphology and meristematic activity of the young shoots of both Marquillo × Kenya Farmer 1 and normal Marquillo plants.Within 12 h of the beginning of 16° treatment, damaged cells were visible in the young developing leaf and stem tissues and such cells became numerous after longer periods at 16°. The cells most rapidly destroyed were those surrounding the vascular bundles in both leaf primordia and stem tissues and the extent of damage in a tissue was closely related to the stage of vascular differentiation in the adjacent bundles.Cell division in the apical meristem of the main shoot was inhibited even more rapidly. The proportion of cells dividing and the incorporation of 3H-thymidine into the nuclei of meristem cells decreased rapidly at 16° and the reversibility of these effects was similar to that of the whole plant effects.It is suggested that the cessation of growth in Mql × KF 1 exposed to 16° is due to the lack of cell division and that the permanence of this effect is due to the extensive cell destruction that occurs in the meristematic regions.

Sexual reproduction of Sitka spruce (Picea sitchensis)

1980 ◽  
Vol 58 (8) ◽  
pp. 886-901 ◽  
Author(s):  
John N. Owens ◽  
Marje Molder
Keyword(s):  
Sexual Reproduction ◽  
Female Gametophyte ◽  
Seed Set ◽  
Mature Female ◽  
Picea Sitchensis ◽  
Contributing Factors ◽  
Embryo Abortion ◽  
Male And Female ◽  
Cell Divisions ◽  
Mother Cells

The phenology of sexual reproduction of Picea sitchensis (Bong.) Carr. was similar at the three sites on Vancouver Island, British Columbia, used in the study. As indicated by cell divisions, cone buds ended dormancy in early March, 2 weeks before dormancy ended in vegetative buds. Pollen mother cells underwent meiosis in mid-March and mature, saccate, four- or five-celled pollen was formed by late April. Megaspore mother cells underwent meiosis in late March and mature female gametophytes were developed by late May. Pollination occurred in late April. A pollination drop was produced by the nucellus and exuded between the two micropylar arms and pollen was drawn down into a nucellar depression where pollen germinated in late April. Fertilization occurred in early June and early stages of embryo development occurred by late June, 9 weeks after pollination. Cotyledons were initiated in late July and seed was mature by mid-August and shed during the early fall.Development of male and female gametophytes and embryos was similar to patterns shown for other species of Picea. In this study seed set was very poor and resulted primarily from a lack of pollination. Other contributing factors were female gametophyte abortion before fertilization, embryo abortion during early development, and insect damage.

Development and Determination of Hairs and Bristles in the Milkweed Bug, Oncopeltus Fasciatus (Lygaeidae, Hemiptera)

1966 ◽  
Vol 1 (4) ◽  
pp. 475-498 ◽  
Author(s):  
P. A. LAWRENCE
Keyword(s):  
Oncopeltus Fasciatus ◽  
Cytoplasmic Process ◽  
Dense Population ◽  
Electron Microscopic ◽  
German Word ◽  
Cell Divisions ◽  
Microscopic Studies ◽  
Mother Cells ◽  
Proliferative Cell

The term ‘organule’ is proposed as an English equivalent for the German word ‘Kleinorgan’. The different organules on the third sternite of Oncopeltus are described: larvae possess innervated bristles and special sensilla termed ‘chemosensilla’, whereas the adult develops, in addition, a dense population of non-innervated hairs. The hairs, bristles and ‘chemosensilla’ each develop from mother cells which undergo a particular series of differentiative divisions. The course of events is described for each type of organule. Electron-microscopic studies of the fine structure of the outgrowing hairs are described. As in the outgrowth of a scale, longitudinal arrays of microtubules and bundles of fibres are found in the first cytoplasmic process of the trichogen cell. Experiments show that bristle determination occurs between the onset of the moult and the proliferative cell divisions in the epidermis. The period of hair determination is found to occur later than that of the bristles and to be later than the proliferative cell divisions in the last larval stage. A discussion of the results includes a review of the knowledge of differentiative divisions concerned in the formation of organules in other groups of insects, and a consideration of Wigglesworth's theory of bristle determination.

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