scholarly journals Ultrastructural changes in chloroplasts of mesophyll cells of chlorotic and prematurely yellowed leaves of Betula pendula Rothr

2011 ◽  
Vol 72 (4) ◽  
pp. 289-293 ◽  
Author(s):  
Krystyna Przybył ◽  
Krystyna Idzikowska
Keyword(s):  
Electron Density ◽  
Lipid Droplets ◽  
Betula Pendula ◽  
Ultrastructural Changes ◽  
Membrane Systems ◽  
Mesophyll Cells ◽  
Spongy Mesophyll ◽  
Starch Grains ◽  
Interveinal Chlorosis ◽  
The Past

The ultrastructure of chloroplasts was studied in mesophyll cells of the leaves of silver birch (<em>Betula pendula</em>) showing interveinal chlorosis or premature yellowing, in comparison with leaves without symptoms or exhibiting symptoms of natural senescence. The leaves were collected between May 26 to June 7 and additionally in the September 10-12 from the upper part of the crown, from increments of the past four years. No major difference in ultrastructure of chloroplasts was found between spongy and palisade mesophyll cells. The following senescencerelated changes were observed in chloroplasts of prematurely yellowed leaves and showing inteveinal chlorosis: reduced chloroplast size, degeneration of the membrane systems of thylakoids and increased electron density of plastoglobuli. The most electron dark globules (lipid droplets) were found together with starch grains in cells of spongy mesophyll of leaves showing interveinal chlorosis. Abnormal, spherical and rounded chloroplasts with electron-dark inside of thylakoids or the electron-dark stroma between thylakoids were found only in yellowed and chlorotic leaves in spring.

Ultrastructural changes accompany inhibition of proteoglycan synthesis in chondrocytes by Cyclofenil diphenol

1989 ◽  
Vol 92 (2) ◽  
pp. 271-280 ◽  
Author(s):  
C.A. Lancaster ◽  
P.R. Fryer ◽  
S. Griffiths ◽  
R.M. Mason
Keyword(s):  
Endoplasmic Reticulum ◽  
Protein Synthesis ◽  
Electron Density ◽  
Lipid Droplets ◽  
Secretory Pathway ◽  
Ultrastructural Changes ◽  
Proteoglycan Synthesis ◽  
Filamentous Material

Cyclofenil diphenol, a weak non-steroidal oestrogen, profoundly inhibits [35S]proteoglycan synthesis in cultures of Swarm chondrosarcoma chondrocytes under conditions in which protein synthesis is only marginally reduced. In the present experiments it was shown that after a 40-min treatment with Cyclofenil diphenol (90 micrograms ml-1) most of the normally abundant Golgi stacks in these cells disappeared and after 60 min they were absent. After 2–3 h treatment the cisternae of the endoplasmic reticulum (ER) were grossly distended and transformed into large ribosome-studded vesicles containing flocculent and filamentous material. These changes were dependent on the concentration of Cyclofenil and were fully reversible within 21 h of withdrawing the drug. The ultrastructural changes differed in some aspects if protein synthesis was blocked with cycloheximide for 15 min or 180 min before and during treatment with Cyclofenil. The Golgi disappeared but the ER cisternae, though distended, formed a continuous network and swollen ribosome-studded vesicles did not develop. However, non-membrane-bounded structures containing lipid droplets and material of low electron density developed in the cytoplasm under these conditions. The ultrastructural changes induced by Cyclofenil differ from those induced by monensin and diethylcarbamazine, suggesting that the drug acts at a different point in the secretory pathway for macromolecules.

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.

scholarly journals Cell wall and organelle modifications during nitrogen starvation in Nannochloropsis oceanica F&M-M24

2021 ◽  
Author(s):  
Roncaglia Bianca ◽  
Papini Alessio ◽  
Chini Zittelli Graziella ◽  
Rodolfi Liliana ◽  
Mario R. Tredici
Keyword(s):  
Cell Wall ◽  
Wall Thickness ◽  
Lipid Droplets ◽  
Nitrogen Starvation ◽  
Photosynthetic Apparatus ◽  
Ultrastructural Changes ◽  
Total Biomass ◽  
Nannochloropsis Oceanica ◽  
Final Phase ◽  
Cell Functions

AbstractNannochloropsis oceanica F&M-M24 is able to increase its lipid content during nitrogen starvation to more than 50% of the total biomass. We investigated the ultrastructural changes and the variation in the content of main cell biomolecules that accompany the final phase of lipid accumulation. Nitrogen starvation induced a first phase of thylakoid disruption followed by chloroplast macroautophagy and formation of lipid droplets. During this phase, the total amount of proteins decreased by one-third, while carbohydrates decreased by 12–13%, suggesting that lipid droplets were formed by remodelling of chloroplast membranes and synthesis of fatty acids from carbohydrates and amino acids. The change in mitochondrial ultrastructure suggests also that these organelles were involved in the process. The cell wall increased its thickness and changed its structure during starvation, indicating that a disruption process could be partially affected by the increase in wall thickness for biomolecules recovery from starved cells. The wall thickness in strain F&M-M24 was much lower than that observed in other strains of N. oceanica, showing a possible advantage of this strain for the purpose of biomolecules extraction. The modifications following starvation were interpreted as a response to reduction of availability of a key nutrient (nitrogen). The result is a prolonged survival in quiescence until an improvement of the environmental conditions (nutrient availability) allows the rebuilding of the photosynthetic apparatus and the full recovery of cell functions.

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]

The ultrastructure of M1-a-mediated resistance to powdery mildew infection in barley

1975 ◽  
Vol 53 (22) ◽  
pp. 2589-2597 ◽  
Author(s):  
H. H. Edwards
Keyword(s):  
Powdery Mildew ◽  
Host Cell ◽  
Electron Density ◽  
Epidermal Cells ◽  
Dense Material ◽  
Ultrastructural Changes ◽  
Electron Dense Material ◽  
Host Cytoplasm ◽  
Powdery Mildew Infection ◽  
Cell Protoplast

M1-a-mediated resistance in barley to invasion by the CR3 race of Erysiphe graminis f. sp. hordei does not occur in every host cell with the same speed and severity. In some cells ultrastructural changes within the host cell as a result of resistance will occur within 24 h after inoculation, whereas in other cells these changes may take up to 72 h. In some cells the ultrastructural changes are so drastic that they give the appearance of a hypersensitive death of the host cell, whereas in other cells the changes are very slight. In any case, at the end of these changes the fungus ceases growth. The ultrastructural changes occur in penetrated host epidermal cells as well as non-infected adjacent epidermal and mesophyll cells.The following ultrastructural changes have been observed: (1) an electron-dense material which occurs either free in the vacuole or adhering to the tonoplast (the material is granular or in large clumps); (2) an increased electron density of the host cytoplasm and nucleus; (3) a breakdown of the tonoplast so that the cytoplasmic constituents become dispersed throughout the cell lumen; and (4) the deposition of papillar-like material in areas other than the penetration site. The first three changes take place within the host cell protoplasts and are directly attributable to the gene M1-a. These changes are typical of stress or incompatibility responses and thus M1-a appears to trigger a generalized incompatibility response in the presence of race CR3. The papillar-like material occurs outside the host cell protoplast in the same manner as the papilla and probably is not directly attributable to M1-a.

scholarly journals Quantum Crystallography in the Last Decade: Developments and Outlooks

Crystals ◽  
2020 ◽  
Vol 10 (6) ◽  
pp. 473 ◽  
Author(s):  
Alessandro Genoni ◽  
Piero Macchi
Keyword(s):  
Electron Density ◽  
Review Article ◽  
Quantum Mechanical ◽  
Spin Models ◽  
The Past ◽  
Core Electrons ◽  
Mechanical Information ◽  
Quantum Crystallography ◽  
Density Modelling

In this review article, we report on the recent progresses in the field of quantum crystallography that has witnessed a massive increase of production coupled with a broadening of the scope in the last decade. It is shown that the early thoughts about extracting quantum mechanical information from crystallographic experiments are becoming reality, although a century after prediction. While in the past the focus was mainly on electron density and related quantities, the attention is now shifting toward determination of wavefunction from experiments, which enables an exhaustive determination of the quantum mechanical functions and properties of a system. Nonetheless, methods based on electron density modelling have evolved and are nowadays able to reconstruct tiny polarizations of core electrons, coupling charge and spin models, or determining the quantum behaviour at extreme conditions. Far from being routine, these experimental and computational results should be regarded with special attention by scientists for the wealth of information on a system that they actually contain.

THE PHYSIOLOGY OF HOST–PARASITE RELATIONS: XVI. FINE STRUCTURE OF THE NUCLEUS IN THE RUST-INFECTED MESOPHYLL CELLS OF WHEAT

1966 ◽  
Vol 44 (5) ◽  
pp. 669-673 ◽  
Author(s):  
M. S. Manocha ◽  
Michael Shaw
Keyword(s):  
Electron Microscopy ◽  
Fine Structure ◽  
Electron Density ◽  
Mesophyll Cells ◽  
Host Parasite ◽  
Late Stages ◽  
Dense Chromatin

The nuclei in rust-infected mesophyll cells of Little Club wheat were examined by electron microscopy. There was a marked increase in the electron density of the diffuse, interchromatin regions of the nuclei at a stage in rust development (8 days after inoculation) at which two- to three-fold increases in RNA are known to occur. In the late stages of rust development (20 to 23 days after inoculation) the interchromatin material disappeared and the dense chromatin disintegrated.

Acid rain effects on foliar histology of Artemisia tilesii

1984 ◽  
Vol 62 (3) ◽  
pp. 463-474 ◽  
Author(s):  
C. M. Adams ◽  
N. G. Dengler ◽  
T. C. Hutchinson
Keyword(s):  
Acid Rain ◽  
Fungal Pathogens ◽  
Leaf Tissue ◽  
Epidermal Cells ◽  
Simulated Acid Rain ◽  
Scanning Electron Micrographs ◽  
Mesophyll Cells ◽  
Spongy Mesophyll ◽  
Abnormal Cell ◽  
Naturally Occurring

The present study describes the effects of simulated acid rain (pH 2.5–5.6) on foliar histology of an arctic herb, Artemisia tilesii Ledeb., which is remarkably tolerant to naturally occurring atmospheric acidity at Smoking Hills, N.W.T. Plants were exposed to simulated acid rain twice weekly for 4 weeks in exposure chambers in the greenhouse. Droplets as acidic as pH 2.5 caused limited macroscopic foliar damage. However, much greater damage was observed when sectioned leaf tissue was examined microscopically. On leaves having no injury visible to the unaided eye, small lesions consisting of one to three collapsed epidermal cells were observed in scanning electron micrographs and in cleared leaves after exposure to rain of pH 3.0 and 3.5. Stomata remained open in damaged areas of acid-sprayed leaves. Lesions most commonly developed from an initial collapse of a few adaxial epidermal cells, followed by progressive injury of underlying tissues. Palisade and spongy mesophyll cells underwent hypertrophic (abnormal cell enlargement) and hyperplastic (abnormal cell division) responses in the region adjacent to severely collapsed tissue, causing reduced intercellular spaces. These effects isolated the injured areas from adjacent healthy tissues, and resembled wound periderm responses to fungal pathogens and to mechanical irritation. This response may be one mechanism of limiting acid rain damage.

scholarly journals Do food trichomes occur in Pinguicula (Lentibulariaceae) flowers?

2020 ◽  
Vol 126 (6) ◽  
pp. 1039-1048
Author(s):  
Krzysztof Lustofin ◽  
Piotr Świątek ◽  
Piotr Stolarczyk ◽  
Vitor F O Miranda ◽  
Bartosz J Płachno
Keyword(s):  
Dna Sequences ◽  
Lipid Droplets ◽  
Glandular Trichomes ◽  
Phylogenetic Reconstruction ◽  
Protein Bodies ◽  
Food Material ◽  
Starch Grains ◽  
Floral Reward ◽  
Food Reserves

Abstract Background and Aims Floral food bodies (including edible trichomes) are a form of floral reward for pollinators. This type of nutritive reward has been recorded in several angiosperm families: Annonaceae, Araceae, Calycanthaceae, Eupomatiaceae, Himantandraceae, Nymphaeaceae, Orchidaceae, Pandanaceae and Winteraceae. Although these bodies are very diverse in their structure, their cells contain food material: starch grains, protein bodies or lipid droplets. In Pinguicula flowers, there are numerous multicellular clavate trichomes. Previous authors have proposed that these trichomes in the Pinguicula flower play the role of ‘futterhaare’ (‘feeding hairs’) and are eaten by pollinators. The main aim of this study was to investigate whether the floral non-glandular trichomes of Pinguicula contain food reserves and thus are a reward for pollinators. The trichomes from the Pinguicula groups, which differ in their taxonomy (species from the subgenera: Temnoceras, Pinguicula and Isoloba) as well as the types of their pollinators (butterflies/flies and bees/hummingbirds), were examined. Thus, it was determined whether there are any connections between the occurrence of food trichomes and phylogeny position or pollination biology. Additionally, we determined the phylogenetic history of edible trichomes and pollinator evolution in the Pinguicula species. Methods The species that were sampled were: Pinguicula moctezumae, P. esseriana, P. moranensis, P. emarginata, P. rectifolia, P. mesophytica, P. hemiepiphytica, P. agnata, P. albida, P. ibarrae, P. martinezii, P. filifolia, P. gigantea, P. lusitanica, P. alpina and P. vulgaris. Light microscopy, histochemistry, and scanning and transmission electron microscopy were used to address our aims with a phylogenetic perspective based on matK/trnK DNA sequences. Key Results No accumulation of protein bodies or lipid droplets was recorded in the floral non-glandular trichomes of any of the analysed species. Starch grains occurred in the cells of the trichomes of the bee-/fly-pollinated species: P. agnata, P. albida, P. ibarrae, P. martinezii, P. filifolia and P. gigantea, but not in P. alpina or P. vulgaris. Moreover, starch grains were not recorded in the cells of the trichomes of the Pinguicula species that have long spurs, which are pollinated by Lepidoptera (P. moctezumae, P. esseriana, P. moranensis, P. emarginata and P. rectifolia) or birds (P. mesophytica and P. hemiepihytica), or in species with a small and whitish corolla that self-pollinate (P. lusitanica). The results on the occurrence of edible trichomes and pollinator syndromes were mapped onto a phylogenetic reconstruction of the genus. Conclusion Floral non-glandular trichomes play the role of edible trichomes in some Pinguicula species (P. agnata, P. albida, P. ibarrae, P. martinezii, P. filifolia and P. gigantea), which are mainly classified as bee-pollinated species that had originated from Central and South America. It seems that in the Pinguicula that are pollinated by other pollinator groups (Lepidoptera and hummingbirds), the non-glandular trichomes in the flowers play a role other than that of a floral reward for their pollinators. Edible trichomes are symplesiomorphic for the Pinguicula species, and thus do not support a monophyletic group such as a synapomorphy. Nevertheless, edible trichomes are derived and are possibly a specialization for fly and bee pollinators by acting as a food reward for these visitors.

Insect–fungus blister galls on Solidago graminifolia and S. rugosa. I. A macroscopic and light microscopic study of the host–parasite relationship

1981 ◽  
Vol 59 (12) ◽  
pp. 2466-2477 ◽  
Author(s):  
Russell R. Camp
Keyword(s):  
Microscopic Study ◽  
Leading Edge ◽  
Mesophyll Cells ◽  
Starch Grains ◽  
Differentiated Cells ◽  
Fungal Hyphae ◽  
Host Parasite Relationship ◽  
Parasite Relationship ◽  
Host Parasite ◽  
Black Region

The host–parasite relations of an insect–fungus blister gall on Solidago graminifolia and a related gall on S. rugosa were studied. The midge, Asteromyia carbonifera, and fungus, Sclerotium asteris, were associated with both gall types.Externally, young galls of both types had a black center surrounded by a yellow halo. During growth in diameter the external coloration did not change in S. graminifolia; however, in S. rugosa a beige – ashy grey area developed in the center of the black region and expanded outward. In both species the leading edge of intercellular fungal hyphae was present in the halo region. Behind this front, hyphae sequestered to form an undifferentiated subepidermal stroma. The stroma differentiated into a black cortex and underlying white medulla at the margin of the black region. Differentiated cells remained subepidermal in both species except for the cortex that became subcuticular in S. graminifolia. During cortical proliferation in S. graminifolia the cuticle remained intact; however, epidermal cells became isolated and collapsed. In S. rugosa the epidermis separated extensively from the mesophyll but remained intact. Mesophyll cells within the halo and black region exhibited a reduction in number and size of chloroplasts and starch grains in both species.

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