Effets physiologiques de l'atrazine à doses sublétales sur Lemna minor. V. Influence sur l'ultrastructure des chloroplastes

1980 ◽  
Vol 58 (14) ◽  
pp. 1571-1577 ◽  
Author(s):  
G. Beaumont ◽  
A. Lord ◽  
G. Grenier
Keyword(s):  
Lemna Minor ◽  
Sublethal Concentration ◽  
Ultrastructural Changes ◽  
Dense Network ◽  
Mesophyll Cells ◽  
Mineral Solution

A sublethal concentration of 0.25 ppm of atrazine produced many ultrastructural changes on the chloroplasts of mesophyll cells of Lemna minor L., cultivated aseptically in a mineral solution. The number of grana per chloroplast increased, whereas the intralamellar vesicles disappeared and outgrowths formed at the ends of chloroplasts. The grana of treated chloroplasts showed a reduction in the number of lamellae and formed a very dense network. The stroma of the same chloroplasts was reduced and accumulated osmiophilic globules.

Ultrastructure and Senescence in an Achloroplastic Mutant of Hordeum vulgare L. cv. Dyan

1992 ◽  
Vol 50 (1) ◽  
pp. 844-845
Author(s):  
R.H.M. Cross ◽  
C.E.J. Botha ◽  
A.K. Cowan ◽  
B.J. Hartley
Keyword(s):  
Cell Wall ◽  
Hordeum Vulgare ◽  
Leaf Tissue ◽  
Ultrastructural Changes ◽  
Hordeum Vulgare L ◽  
Mesophyll Cells ◽  
Lethal Mutant ◽  
Cytoplasmic Matrix ◽  
Close Proximity ◽  
Pinocytotic Vesicles

Senescence is an ordered degenerative process leading to death of individual cells, organs and organisms. The detection of a conditional lethal mutant (achloroplastic) of Hordeum vulgare has enabled us to investigate ultrastructural changes occurring in leaf tissue during foliar senescence.Examination of the tonoplast structure in six and 14 day-old mutant tissue revealed a progressive degeneration and disappearance of the membrane, apparently starting by day six in the vicinity of the mitochondria associated with the degenerating proplastid (Fig. 1.) where neither of the plastid membrane leaflets is evident (arrows, Fig. 1.). At this stage there was evidence that the mitochondrial membranes were undergoing retrogressive changes, coupled with disorganization of cristae (Fig. 2.). Proplastids (P) lack definitive prolamellar bodies. The cytoplasmic matrix is largely agranular, with few endoplasmic reticulum (ER) cisternae or polyribosomal aggregates. Interestingly, large numbers of actively-budding dictysomes, associated with pinocytotic vesicles, were observed in close proximity to the plasmalemma of mesophyll cells (Fig. 3.). By day 14 however, mesophyll cells showed almost complete breakdown of subcellular organelle structure (Fig. 4.), and further evidence for the breakdown of the tonoplast. The final stage of senescence is characterized by the solubilization of the cell wall due to expression and activity of polygalacturonase and/or cellulose. The presence of dictyosomes with associated pinocytotic vesicles formed from the mature face, in close proximity to both the plasmalemma and the cell wall, would appear to support the model proposed by Christopherson for the secretion of cellulase. This pathway of synthesis is typical for secretory glycoproteins.

ULTRASTRUCTURAL CHANGES IN CHLOROPLASTS OF AUTUMN LEAVES

1971 ◽  
Vol 13 (3) ◽  
pp. 550-559 ◽  
Author(s):  
Mark E. Stearns ◽  
E. B. Wagenaar
Keyword(s):  
Populus Tremuloides ◽  
Ultrastructural Changes ◽  
Starch Granules ◽  
Membrane Structures ◽  
Mesophyll Cells ◽  
Stroma Lamellae ◽  
Typical Summer ◽  
Palisade Cells ◽  
Acer Ginnala ◽  
Rhus Typhina

The phenomenon of aging of leaves in autumn was studied in three deciduous trees, viz. Acer ginnala Maxim., Populus tremuloides Michx. and Rhus typhina L. The leaves were collected at three stages of development: at maximum summer development, at early senescence, and at a full senescence. Electron microscope studies of fully matured leaves generally showed lens-shaped chloroplasts fairly uniform in shape and size with extensive granalamellae, large starch granules and a few small lipid globules. Green, partly senescent leaves had somewhat smaller chloroplasts with large lipid globules within the reduced stroma-lamellae; virtually no starch granules were present. Fully senescent, brightly coloured, autumn leaves showed a definite decrease in size and number of chloroplasts. These plastids had lost their typical summer structure, were small and cylindrical, and contained densely packed globules that replaced the membrane structures. The presence of the carotenoids in these globules probably contributed to the autumn pigmentation of the leaves. Not all leaf cells followed the above described pattern of senescence at the same rate. The chloroplasts of palisade cells degraded earlier than those in the mesophyll cells.

Degeneration of leaf cells resulting from starvation after excision. I. Electron microscopic observations

1970 ◽  
Vol 48 (11) ◽  
pp. 1913-1922 ◽  
Author(s):  
H. W. J. Ragetli ◽  
M. Weintraub ◽  
Esther Lo
Keyword(s):  
Nuclear Membrane ◽  
Nuclear Material ◽  
Ultrastructural Changes ◽  
Cell Aging ◽  
Starvation Stress ◽  
Electron Microscopic ◽  
Nicotiana Glutinosa ◽  
Mesophyll Cells ◽  
Unequal Distribution ◽  
3 Dimensional

Mesophyll cells of Nicotiana glutinosa exposed to starvation in the light after leaf excision showed the following major changes: vacuolation of the cytoplast; rearrangement of chloroplast and nuclear material; accumulation of cytoplasmic crystals and of starch; evagination and increased perforation of the nuclear membrane; and lysis of the tonoplast. Rearrangement of chloroplast material resulted in extended, 3-dimensional arrays (pseudocrystalline bodies), composed of electron-dense globules 85–100 Å in diameter. The ultrastructural degeneration of cells within a leaf was unsynchronized, and the sequence of degenerative intracellular events was not fixed. These observations are compatible with an unequal distribution of "essential" metabolites among those cells. Cells suffering from starvation stress showed ultrastructural changes not observed in cells of aging attached leaves and vice versa. Thus, starvation stress does not merely accelerate the process of cell-aging, as it operates in attached leaves.

Étude ultrastructurale des modifications induites par Exserohilum turcicum chez le limbe de Zea mays – Effet du gène de résistance Ht-1

1987 ◽  
Vol 65 (10) ◽  
pp. 2061-2066
Author(s):  
B. Gélie ◽  
M. Petitprez ◽  
A. Souvre ◽  
L. Albertini
Keyword(s):  
Zea Mays ◽  
Comparative Study ◽  
Inbred Lines ◽  
Bundle Sheath ◽  
Ultrastructural Changes ◽  
Exserohilum Turcicum ◽  
Mesophyll Cells ◽  
Isogenic Lines ◽  
Bundle Sheath Cells ◽  
Cellular Components

Ultrastructural changes induced by Exserohilum turcicum (Pass.) Leonard et Suggs in maize leaf cells are observed 24 to 72 h after inoculation, in a comparative study between two isogenic lines with or without the Ht-1 gene. In the susceptible plants (without Ht-1), the plasmalemma and the tonoplast of the mesophyll cells are the first cellular components altered, followed by disorganisation and alteration of organelles, which become scattered throughout the cell. Chloroplasts in particular seem to be very sensitive to the toxic action of the pathogen, which causes disruption of their envelope and grana. Bundle sheath cells are altered later and to a lesser extent than the mesophyll cells. In Ht-1 monogenic resistant inbred lines, cytoplasmic residues of prematurely dead cells surround healthy mesophyll cells protecting them and stimulating their activity and resulting in stabilization of the pathotoxic process 36 to 48 h after inoculation.

scholarly journals Morphological and Ultrastructural Changes of Organelles in Leaf Mesophyll Cells of the Arctic and Antarctic Plants of Poaceae Family Under Cold Influence

2015 ◽  
Vol 47 (1) ◽  
pp. 17-25 ◽  
Author(s):  
Irena Giełwanowska ◽  
Marta Pastorczyk ◽  
Wioleta Kellmann-Sopyła ◽  
Dorota Górniak ◽  
Ryszard J. Górecki
Keyword(s):  
The Arctic ◽  
Ultrastructural Changes ◽  
Mesophyll Cells ◽  
Antarctic Plants ◽  
Leaf Mesophyll ◽  
Poaceae Family

Inhibition of chlorophyll synthesis in Lemna minor by nalidixic acid

1975 ◽  
Vol 53 (20) ◽  
pp. 2319-2324 ◽  
Author(s):  
Hugh Frick ◽  
Raymond F. Jones
Keyword(s):  
Nalidixic Acid ◽  
Normal Individual ◽  
Lemna Minor ◽  
Chlorophyll Synthesis ◽  
Heterotrophic Growth ◽  
Free Medium ◽  
Mesophyll Cells ◽  
Normal Cells ◽  
Dense Cytoplasm ◽  
Rates Of Growth

Nalidixic acid bleached Lemna minor during growth in white light on a medium supporting heterotrophic growth. Immature, vacuolate mesophyll cells from bleached tissue contained plastids with aberrant thylakoids and had less-electron-dense cytoplasm than normal cells. Mitochondrial shape appeared normal. Individual bleached plants regreened and regained normal rates of growth after transfer to nalidixic-acid- (NAL-) free medium. Frond multiplication was also inhibited by NAL during growth in darkness. Purine and pyrimidine ribonucleosides did not prevent NAL-induced bleaching or growth inhibition.

Changes in the plastid ultrastructure during greening in cultured soybean cells

1989 ◽  
Vol 47 ◽  
pp. 1010-1011
Author(s):  
M.A. Gillott ◽  
G. Erdös ◽  
D. E. Buetow
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Gene Regulation ◽  
Uranyl Acetate ◽  
Total Darkness ◽  
Ultrastructural Changes ◽  
Ethanol Dehydration ◽  
Mesophyll Cells ◽  
Plastid Ultrastructure ◽  
Transmission Electron

Mesophyll cells isolated from soybeans (Glycine max, L. Merr. var. Corsoy) can be grown photoautotrophically in suspension culture. The SB-P cell line can be bleached by maintaining them in total darkness in sucrose supplemented media for several weeks, and will regain photosynthetic competency when returned to the light. This system is ideally suited for the study of gene regulation and the biochemical and ultrastructural changes which occur during the greening process.Cells were fixed for electron microscopy after 8 weeks of growth in total darkness and at intervals of 1 h to 12 d after transfer to the light. Chlorophyll measurements were determined for each sample. For transmission electron microscopy, the cells were fixed for 1-2 h in 4% glutaraldehyde in 0.1M Pipes buffer, pH 7.4, washed in the same buffer, then postfixed for 1 h in 1% OsO4 in Pipes, pH 6.8. Following a graded ethanol dehydration series the cells were transferred into propylene oxide and embedded in Epon. Sections were stained with uranyl acetate and observed on a JEOL 100C TEM operated at 80 kV.

Fine structure of sunflower crown gall tissue

1970 ◽  
Vol 48 (8) ◽  
pp. 1455-1458 ◽  
Author(s):  
M. S. Manocha
Keyword(s):  
Crown Gall ◽  
Electron Microscopic Examination ◽  
Mesophyll Cell ◽  
Ultrastructural Changes ◽  
Bacterial Inoculation ◽  
Electron Microscopic ◽  
Mesophyll Cells ◽  
Thin Sections ◽  
Gall Tissue ◽  
Crown Gall Tissue

Electron microscopic examination of thin sections from sunflower crown gall tissue, induced by Agrobacterium tumefaciens, revealed certain details about its intracellular organization not previously reported. Tumor tissue showed a marked increase in the number of ribosomes, endoplasmic reticulum, and Golgi dictyosomes, over that of normal mesophyll cells. Mitochondria and chloroplasts did not show any detectable change. Crystalline bodies, consisting of a lattice surrounded by a unit membrane, were frequently observed in tumorous cells. The nucleoli of tumor cells contained vacuoles and were clearly differentiated into two zones, pars amorpha and nucleolonema. The possible significance of these ultrastructural changes has been discussed. Small vesicle-like bodies were observed in the nuclei of mesophyll cells 4 days after bacterial inoculation. Whether or not these vesicle-like bodies are responsible for the transformation of a normal mesophyll cell to a fully autonomous tumor cell is not known, but the possibility is an intriguing one.

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