Accroissement de la résistance au froid (jusqu'à −30 °C) de plantules de Blé avec un milieu cryoprotecteur. Effets de ce traitement sur les ultrastructures de cellules parenchymateuses d'ébauches foliaires

1980 ◽  
Vol 58 (23) ◽  
pp. 2520-2532 ◽  
Author(s):  
C. M. Gazeau
Keyword(s):  
Leaf Primordia ◽  
Cold Temperature ◽  
Ultrastructural Changes ◽  
Wheat Seedlings ◽  
Parenchyma Cells ◽  
Mitotic Figures ◽  
Peripheral Cytoplasm ◽  
Peripheral Regions

Wheat seedlings treated with a frost-protecting medium containing a mixture of glycerol, dimethyl sulfoxyde, and saccharose, were subjected to cooling at the rate of 1 °C/min during a few hours. Seedlings treated in this way were resistant to temperatures of −30 °C. However on rewarming, the growth of leaves and coleoptiles was slightly slowed down compared with that of control seedlings.Seedling impregnation with the frost-protecting medium provoked few ultrastructural changes in the parenchyma cells of leaf primordia. Only lipidic, osmiophilic globules were relatively abundant, and these were scattered in the peripheral cytoplasm, along the plasmalemma. Cooling to −30 °C tended to make certain organelles migrate preferentially towards peripheral regions; the plasmalemma, osmiophilic globules, microtubules, and mitochondria came into contact with each other. In spite of the very cold temperature, some mitotic figures persisted with no evident signs of changes.On rewarming the seedlings, the various changes observed during cold treatments gradually diminished and disappeared. [Journal translation]

Influence de la température et de la durée d'un traitement cryoprotecteur sur la résistance au froid de plantules de blé. Étude ultrastructurale des ébauches foliaires

1983 ◽  
Vol 61 (4) ◽  
pp. 1025-1039 ◽  
Author(s):  
C. M. Gazeau
Keyword(s):  
Endoplasmic Reticulum ◽  
Treatment Period ◽  
Day Treatment ◽  
Leaf Primordia ◽  
Ultrastructural Changes ◽  
Distilled Water ◽  
Wheat Seedlings ◽  
Starch Grains ◽  
Different Temperatures ◽  
Protective Treatment

Wheat seedlings were treated at different temperatures and for various periods of time with a cold-protective substance, composed of a mixture of glycerol, dimethylsulfoxide, and saccharose. When the treatment was done at 20 °C, slight ultrastructural changes appeared in leaf primordia as soon as day 1. Thus numbers of lipid globules increased significantly. When the treatment period was increased to 4 days, numbers of starch grains increased, and there was a marked enlargement of mitochondria and plasts. When the treatment was done at 2 °C, cytoplasmic alterations occurred later than at 20 °C. After a 4-day treatment, they were similar to changes induced at 20 °C. When the treatment period was increased to 12 days, dictyosomes were markedly altered. They clustered close to the nucleus in two or three groups and gave rise to numerous pale vesicles with various shapes and sizes. Around each cluster of such vesicles, there gathered many endoplasmic reticulum vesicles and other organelles (mitochondria, plasts, microbodies, vacuoles). A further cooling of 1 °C/min, down to −15 or −30 °C, enhanced these phenomena. After the seedlings were warmed up to 20 °C in distilled water, the changes induced by the frost-protective treatment and then by freezing were shown to be reversible. [Journal translation]

Ultrastructural Changes in the Cell Walls of Cambial Derivatives During Wood Formation in Indian ELM (Holoptelea Integrifolia)

IAWA Journal ◽  
2012 ◽  
Vol 33 (4) ◽  
pp. 403-416 ◽  
Author(s):  
Karumanchi S. Rao ◽  
Yoon Soo Kim ◽  
Pramod Sivan
Keyword(s):  
Cell Wall ◽  
Cell Walls ◽  
Middle Lamella ◽  
Ultrastructural Changes ◽  
Cell Wall Polysaccharides ◽  
Lignin Distribution ◽  
Parenchyma Cells ◽  
Ray Cells ◽  
Xylem Elements ◽  
S2 Layer

Sequential changes occurring in cell walls during expansion, secondary wall (SW) deposition and lignification have been studied in the differentiating xylem elements of Holoptelea integrifolia using transmission electron microscopy. The PATAg staining revealed that loosening of the cell wall starts at the cell corner middle lamella (CCML) and spreads to radial and tangential walls in the zone of cell expansion (EZ). Lignification started at the CCML region between vessels and associated parenchyma during the final stages of S2 layer formation. The S2 layer in the vessel appeared as two sublayers,an inner one and outer one.The contact ray cells showed SW deposition soon after axial paratracheal parenchyma had completed it, whereas noncontact ray cells underwent SW deposition and lignification following apotracheal parenchyma cells. The paratracheal and apotracheal parenchyma cells differed noticeably in terms of proportion of SW layers and lignin distribution pattern. Fibres were found to be the last xylem elements to complete SW deposition and lignification with differential polymerization of cell wall polysaccharides. It appears that the SW deposition started much earlier in the middle region of the fibres while their tips were still undergoing elongation. In homogeneous lignin distribution was noticed in the CCML region of fibres.

Ultrastructural changes in shoot apex cells of winter wheat seedlings during ice encasement

1978 ◽  
Vol 56 (7) ◽  
pp. 786-794 ◽  
Author(s):  
M. Keith Pomeroy ◽  
Chris J. Andrews
Keyword(s):  
Endoplasmic Reticulum ◽  
Winter Wheat ◽  
Structural Integrity ◽  
Triticum Aestivum L ◽  
Ultrastructural Changes ◽  
Wheat Seedlings ◽  
Contrast Exposure ◽  
Ice Encasement ◽  
Cold Hardy ◽  
Cellular Organelles

The decline in viability of cold-hardy Kharkov winter wheat (Triticum aestivum L.) seedlings during ice encasement at −1 °C was accompanied by characteristic ultrastructural changes. A dramatic increase in endoplasmic reticulum was observed within a few days. This proliferation of endoplasmic reticulum often resulted in the formation of an elaborate series of parallel membranes, either dispersed randomly throughout the cytoplasm or in the form of concentric whorls. However, the structural integrity of many cellular organelles was largely unaffected even by prolonged ice encasement resulting in death of the plants. In contrast, exposure of cold-hardy seedlings to near lethal, subfreezing temperature resulted in severe disorganization of cellular organelles. Ice encasement of nonhardened seedlings resulted in complete kill within 4 h. After 16 h ice encasement, occasional concentric whorls of endoplasmic reticulum and copious amounts of osmiophilic material were observed in the cytoplasm. Upon removal of the ice encasement stress, the accumulated endoplasmic reticulum disappeared rapidly during recovery at either2 or20 °C.

Effect of cycloheximide on the freezing tolerance and ultrastructure of cortical parenchyma cells from mulberry twigs

1983 ◽  
Vol 61 (8) ◽  
pp. 2205-2211 ◽  
Author(s):  
T. Niki ◽  
A. Sakai
Keyword(s):  
Freezing Tolerance ◽  
Ultrastructural Changes ◽  
Cortical Cells ◽  
Cytological Change ◽  
Cortical Parenchyma ◽  
Parenchyma Cells ◽  
Cytological Changes ◽  
The Relationship ◽  
Further Development ◽  
In Cells

Experiments were performed using cycloheximide (CHI) on cortical parenchyma cells from mulberry twigs (Morus bombyciz cv. Gorogi) to understand the relationship between the sequence of cytological changes suggesting replacement of the plasmamembrane and the rapid increase in freezing tolerance. Cortical cells from twigs collected on October 16 and 27, which were hardy to −10 and −15 °C, respectively, were still alive after cooling to −70 °C if they had been exposed to −3 °C for 10 to 12 days. In these hardened cells, appearance of microvesicles (MVs) in the peripheral cytoplasm and fusion of these MVs with plasmamembrane were characteristically observed. Neither cytological change nor increase of freezing tolerance was observed in cells treated by CHI before their exposure to −3 °C for 10 to 12 days. However, the suppression of such changes by CHI treatment was effective only in cells which were hardy at −10 to −15 °C and not in the cells of twigs collected on November 4, which were hardy to −20 °C. Consequently, synthesis of some functional proteins during hardening was required for the further development of freezing tolerance, and synthesis had been accomplished before the cells became hardy to −20 °C. Ultrastructural changes brought about by CHI treatment suggest that synthesis of some functional proteins related to the presumed changes of plasmamembrane occurs during hardening.

Influence de la température et de la durée d'un traitement cryoprotecteur sur la résistance au froid de plantules de blé. Étude ultrastructurale des nucléoles des ébauches foliaires

1985 ◽  
Vol 63 (4) ◽  
pp. 663-671 ◽  
Author(s):  
Claude-Madeleine Gazeau
Keyword(s):  
Dimethyl Sulfoxide ◽  
Low Temperatures ◽  
Leaf Primordia ◽  
Distilled Water ◽  
Wheat Seedlings ◽  
Cryoprotective Agent

The nucleolus is sensitive to cold-protective media and to low temperatures. Nucleolar changes observed in the leaf primordia of wheat seedlings were related to the impregnation medium (distilled water or a mixture of glycerol, dimethyl sulfoxide, and sucrose), to the temperature (20 or 2 °C), and to the duration of the pretreatment (1 to 12 days). The cryoprotective agent generated the formation of nucleoli "with a diffuse granular zone." If the impregnation was done at 2 °C, characteristic nucleoli "with an indented aspect" occurred. The longer the duration of the impregnation and the more intense the subsequent freezing, the more important were the nucleolar changes. On rewarming the seedlings the various transformations were shown to be reversible.

scholarly journals ON THE FINE STRUCTURE OF THE CAMBIUM OF FRAXINUS AMERICANA L

1966 ◽  
Vol 31 (1) ◽  
pp. 79-93 ◽  
Author(s):  
Lalit M. Srivastava
Keyword(s):  
Endoplasmic Reticulum ◽  
Fine Structure ◽  
Osmium Tetroxide ◽  
Coated Vesicles ◽  
Fraxinus Americana ◽  
Parenchyma Cells ◽  
Rough Er ◽  
Cambial Cells ◽  
Peripheral Cytoplasm

The fine structure of ash cambium was studied after glutaraldehyde-osmium tetroxide fixation. The fusiform and ray initials are essentially alike, and both have the basic complement of organelles and membranes typical of parenchyma cells. The varied behavior of the two types of initials and the role of cambium in oriented production of the xylem and phloem are still unexplained phenomena. Actively growing cambial cells are highly vacuolate. They are rich in endoplasmic reticulum of the rough cisternal form, ribosomes, dictyosomes, and coated vesicles. Microtubules are present in the peripheral cytoplasm. The plasmalemma appears to be continuous with the endoplasmic reticulum and produces coated vesicles as well as micropinocytotic vesicles with smooth surfaces. The plastids have varying amounts of an intralamellar inclusion which may be a lipoprotein. The quiescent cambium is deficient in rough ER and coated vesicles and has certain structures which may be condensed proteins.

scholarly journals Ultrastructural changes in aster yellows phytoplasma affected Limonium sinuatum Mill. plants II. Pathology of cortex parenchyma cells

2014 ◽  
Vol 70 (4) ◽  
pp. 273-279 ◽  
Author(s):  
Anna Rudzińska-Langwald ◽  
Maria Kamińska
Keyword(s):  
Plasma Membrane ◽  
Ultrastructural Changes ◽  
Internal Space ◽  
Pathological Changes ◽  
Aster Yellows ◽  
Parenchyma Cells ◽  
Aster Yellows Phytoplasma

In <em>Limonium sinuatum</em> Mill, plants with severe symptoms of aster yellows infection phytoplasmas were present not only in the phloem but also in some cortex parenchymas cells. These parenchyma cells were situated at some distance from the conducting bundles. The phytoplasmas were observed directly in parenchyma cells cytoplasm. The number of phytoplasmas present in each selected cell varies. The cells with a small number of phytoplasmas show little pathological changes compared with the unaffected cells of the same zone of the stem as well with the cells of healthy plants. The cells filled with a number of phytoplasmas had their protoplast very much changed. The vacuole was reduced and in the cytoplasm a reduction of the number of ribosomes was noted and regions of homogenous structure appeared. Mitochondria were moved in the direction of the tonoplast and plasma membrane. Compared to the cells unaffected by phytoplasma, the mitochondria were smaller and had an enlarged cristae internal space. The chloroplasts from affected cells had a very significant reduction in size and the tylacoids system had disappeared. The role of these changes for creating phytoplasma friendly enviroment is discused.

Comparative Ultrastructure of Green and Xantha Redwood (Sequoia Sempervirens) Chloroplasts

1975 ◽  
Vol 33 ◽  
pp. 570-571
Author(s):  
Ronald W. Davis ◽  
Gerald W. Lasser ◽  
Charles D. Bower
Keyword(s):  
Electron Microscopy ◽  
Phosphate Buffer ◽  
Sequoia Sempervirens ◽  
Humboldt County ◽  
Normal Green ◽  
Parenchyma Cells ◽  
Accessory Pigment ◽  
Ultrathin Sections ◽  
Comparative Ultrastructure ◽  
Peripheral Cytoplasm

A number of reports have appeared in the literature concerning chlorophyll and accessory pigment deficiencies in plants. These conditions are nearly always fatal as they result in nonfunctional chloroplasts. For this reason it was of considerable interest to find a wild redwood tree (Sequoia sempervirens) living in southern Humboldt County, about 15 feet tall and seemingly completely devoid of pigments.Specimens of normal (green) and mutant (xantha) S. sempervirens leaves were taken for ultrastructural, lipid, and pigment analyses. Specimens were prepared for electron microscopy by placing small pieces of leaves in 5% glutaraldehyde in 0.2M phosphate buffer at pH 7.3 for 24 hours. Postfixation was in 2% OsO4 in phosphate buffer for 6 hours. Dehydration was by a standard acetone series and specimens were embedded in Spurr's LVEM. Ultrathin sections were cut with glass knives on a Reichert Ultramicrotome and examined with a Hitachi HU 11E electron microscope.Chloroplasts of both the green and the mutant leaves were found in the thin layer of peripheral cytoplasm of leaf parenchyma cells.

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