Persistent Calyxes in Postbloom Fruit Drop: A Microscopy and Microanalysis Perspective

Citrus postbloom fruit drop, caused by Colletotrichum spp., is an important disease in the Americas. The pathogen infects citrus flowers, produces orange-brown lesions on petals, and may cause the abscission of young fruit. In diseased flowers, the calyxes remain attached to the peduncle after the young fruit drop. No anatomical and microanalysis studies have been conducted to determine whether calyx tissues can be infected by Colletotrichum spp. and why calyxes remain attached to the peduncle. Based on light microscopy, we demonstrate that the ovary abscission zone exhibits a separation region composed of layers of thickened lignified walled cells, indicating that abscission involves the disruption of cell walls. The first layers of the protective zone (PZ) are composed of densely packed cells with suberized walls produced by the wound meristem. Beneath the PZ, there is a compact mass of small cells that accumulate starch grains. X-ray fluorescence microanalysis (µ-XRF) confirmed the increased accumulation of calcium in the receptacle of the persistent calyxes compared to non-inoculated citrus flowers. Moreover, the peduncle pith and the receptacle exhibit hypertrophied cells with thick walls that may be related to calyx retention. Fungal structures are not observed inside the persistent calyx tissues.

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Structural studies of single wood cell walls by synchrotron X-ray microdiffraction and polarised light microscopy

Nuclear Instruments and Methods in Physics Research Section B Beam Interactions with Materials and Atoms ◽

10.1016/j.nimb.2005.06.011 ◽

2005 ◽

Vol 238 (1-4) ◽

pp. 16-20 ◽

Cited By ~ 13

Author(s):

Marko Peura ◽

Martin Müller ◽

Ritva Serimaa ◽

Ulla Vainio ◽

Matti-Paavo Sarén ◽

...

Keyword(s):

Light Microscopy ◽

Cell Walls ◽

Structural Studies ◽

X Ray ◽

Polarised Light

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Structural studies of Chondrus crispus: the effect of extraction of carrageenan

Canadian Journal of Botany ◽

10.1139/b77-231 ◽

1977 ◽

Vol 55 (15) ◽

pp. 2053-2064 ◽

Cited By ~ 7

Author(s):

E. L. McCandless ◽

W. T. Okada ◽

J. N. A. Lott ◽

C. M. Vollmer ◽

E. M. Gordon-Mills

Keyword(s):

Cell Walls ◽

Cortical Cell ◽

Small Cells ◽

Chondrus Crispus ◽

Structural Studies ◽

Sulphated Polysaccharide ◽

X Ray ◽

Ultrastructural Studies ◽

Intercellular Matrix ◽

Transmission Electron

Birefringence, energy-dispersive x-ray analysis (EDX), and ultrastructural studies were performed on control and on extracted carposporic and tetrasporic Chondrus crispus Stack. thalli.EDX analysis of untreated carposporic and tetrasporic plants revealed the presence of sulphur primarily in the intercellular matrix and cell walls. The sulphur levels detected were greater in tetrasporic than in carposporic plants. EDX analysis of tetrasporic and carposporic plants after extraction with hot aqueous bicarbonate, which should remove most of the sulphated polysaccharide carrageenan, showed little sulphur in walls and intercellular matrices.The microfibrils visible with transmission electron microscopy in cell walls of both generations of C. crispus appeared to run parallel to the cell surface, i.e. circumferentially. Some areas of the intercellular matrix were entirely granular, while others contained microfibrils. After extraction, microfibrils in cell walls and intercellular matrix were disorganized but were still present, perhaps in reduced amounts.The birefringence which characterized the walls of untreated cells was greatly reduced by 2 h extraction, and matrix birefringence was entirely removed. Cortical cell walls could still be identified and stained metachromatically with toluidine blue, but they were no longer birefringent. Further extraction (5 h) removed residual birefringence, but rhizoid cell walls were still metachromatic, as were the remnants of small cells believed to be cortical in origin.

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Ectodesmata as Revealed By Freeze-Etch Preparations of Plant Epidermal Cell Walls

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100072782 ◽

1973 ◽

Vol 31 ◽

pp. 468-469

Author(s):

N.C. Lyon ◽

W. C. Mueller

Keyword(s):

Electron Microscopy ◽

Acetic Acid ◽

Nitric Acid ◽

Oxalic Acid ◽

Light Microscopy ◽

Epidermal Cell ◽

Cell Walls ◽

Plant Viruses ◽

Plant Leaves ◽

Thin Sections

Schumacher and Halbsguth first demonstrated ectodesmata as pores or channels in the epidermal cell walls in haustoria of Cuscuta odorata L. by light microscopy in tissues fixed in a sublimate fixative (30% ethyl alcohol, 30 ml:glacial acetic acid, 10 ml: 65% nitric acid, 1 ml: 40% formaldehyde, 5 ml: oxalic acid, 2 g: mecuric chloride to saturation 2-3 g). Other workers have published electron micrographs of structures transversing the outer epidermal cell in thin sections of plant leaves that have been interpreted as ectodesmata. Such structures are evident following treatment with Hg++ or Ag+ salts and are only rarely observed by electron microscopy. If ectodesmata exist without such treatment, and are not artefacts, they would afford natural pathways of entry for applied foliar solutions and plant viruses.

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X-ray and neutron scattering for studying moisture in the nanostructure of wood cell walls

10.1021/scimeetings.0c05079 ◽

2020 ◽

Author(s):

Paavo Penttilä

Keyword(s):

Neutron Scattering ◽

Cell Walls ◽

X Ray

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Visualising Silicon in Plants: Histochemistry, Silica Sculptures and Elemental Imaging

Cells ◽

10.3390/cells9041066 ◽

2020 ◽

Vol 9 (4) ◽

pp. 1066 ◽

Cited By ~ 2

Author(s):

Gea Guerriero ◽

Ian Stokes ◽

Nathalie Valle ◽

Jean-Francois Hausman ◽

Christopher Exley

Keyword(s):

Cell Walls ◽

Mass Spectrometry Imaging ◽

Spatial Information ◽

Cannabis Sativa ◽

Essential Element ◽

Molecular Data ◽

Plant Vigour ◽

X Ray ◽

Imaging Approach ◽

General Improvement

Silicon is a non-essential element for plants and is available in biota as silicic acid. Its presence has been associated with a general improvement of plant vigour and response to exogenous stresses. Plants accumulate silicon in their tissues as amorphous silica and cell walls are preferential sites. While several papers have been published on the mitigatory effects that silicon has on plants under stress, there has been less research on imaging silicon in plant tissues. Imaging offers important complementary results to molecular data, since it provides spatial information. Herein, the focus is on histochemistry coupled to optical microscopy, fluorescence and scanning electron microscopy of microwave acid extracted plant silica, techniques based on particle-induced X-ray emission, X-ray fluorescence spectrometry and mass spectrometry imaging (NanoSIMS). Sample preparation procedures will not be discussed in detail, as several reviews have already treated this subject extensively. We focus instead on the information that each technique provides by offering, for each imaging approach, examples from both silicifiers (giant horsetail and rice) and non-accumulators (Cannabis sativa L.).

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Non-cellulosic structural polysaccharides in algal cell walls I. Xylan in siphoneous green algae

Proceedings of the Royal Society of London Series B Biological Sciences ◽

10.1098/rspb.1964.0041 ◽

1964 ◽

Vol 160 (980) ◽

pp. 293-313 ◽

Cited By ~ 49

Keyword(s):

Relative Humidity ◽

Cell Walls ◽

Marine Algae ◽

Transverse Section ◽

Algal Cell ◽

Repeat Distance ◽

X Ray ◽

Face View ◽

Half Turn ◽

Parallel Arrays

The cell walls of a number of marine algae, namely species of Bryopsis, Caulerpa, Udotea, Halimeda and Penicillus and of one freshwater alga, Dichotomosiphon , are examined using both chemical and physical techniques. It is shown that, with the possible exception of Bryopsis , cellulose is completely absent and that the walls contain instead β -l,3-linked xylan as the structural polysaccharide. Bryopsis contains, in addition, a glucan which is most abundant in the outer layers of the wall and which stains like cellulose. The xylan is microfibrillar but the microfibrils are more strongly adherent than they are in cellulose, and in some species appear in the electron microscope to be joined by short crossed rod-like bodies. The orientation of the microfibrils is found to vary, ranging from a net tendency to transverse orientation through complete randomness to almost perfect longitudinal alinement. The microfibrils are negatively birefringent, so that all walls seen in optical section, and all parallel arrays of microfibrils whether in face view or in section (except strictly transverse section) are negatively birefringent. With Bryopsis , the negative birefringence in face view is overcompensated by the positive birefringence of the incrusting glucan so that the true birefringence of the crystalline polysaccharide is observed only after the glucan is removed. The X-ray diagram of parallel arrays of microfibrils as found, for instance, in Penicillus dumetosus shows that the xylan chains are helically coiled, in harmony with the negative birefringence. It is deduced that the microfibrils consist of hexagonally packed, double-stranded helices. The diameter of the helices increases with increasing relative humidity, as water is taken into the lattice, from 13.7 Å in material dried over phosphorus pentoxide to a maximum of 1.54 Å at 65 % relative humidity when the xylan contains 30 % of its weight as water. The repeat distance along the helix axis ranges from 5.85 Å (dry) to 6.06 Å (wet), the length of a half turn of each helix containing three xylose residues. The incrusting substances in these walls often include a glucan which is said also to be 1,3-linked. The significance of the extensive differences between this xylan and cellulose are examined both as regards some of the physical properties of the respective cell walls and in relation to the taxonomic position of these plants.

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Putting Molecules in the Picture: Using Correlated Light Microscopy and Soft X-Ray Tomography to Study Cells

Synchrotron Light Sources and Free-Electron Lasers ◽

10.1007/978-3-319-04507-8_43-2 ◽

2019 ◽

pp. 1-32

Author(s):

Axel Ekman ◽

Jian-Hua Chen ◽

Venera Weinhardt ◽

Myan Do ◽

Gerry McDermott ◽

...

Keyword(s):

Light Microscopy ◽

X Ray

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Anatomía de la semilla de Tigridia pavonia (Iridaceae)

Botanical Sciences ◽

10.17129/botsci.1655 ◽

2017 ◽

pp. 66

Author(s):

Aída Carrillo-Ocampo ◽

E.M. Engleman

Keyword(s):

Electron Microscopy ◽

Scanning Electron Microscopy ◽

Light Microscopy ◽

Thin Layer ◽

Cell Walls ◽

Histochemical Staining ◽

Stage Of Development ◽

Scanning Electron

With methods of light microscopy, histochemical staining and scanning electron microscopy, it was found that the ovule in the seed of Tigridia pavonia (Iridaceae) is anatropous, bitegmic, and crassinucellate. During development, the exotegmen is crushed and the endotegmen persists with tannins in the lumens and in the walls, which also react positively for lignin. The exotesta contains tannins and its outer walls are convex, thickened, and cuticularized. The mesotesta has multiple layers, accumulates abundant lipids, and forms a bulge in the chalaza. The cell walls of the endotesta collapse and accumulate tannins. In the chalaza, a hypostasal cushion contains tannins in the lumens and in the walls, which also react positively for lignin. At the micropylar end of the seed there is an operculum which consists of: a) a slightly crushed exotegmen, b) an endotegmen with cuticular thickenings that are concentric with respect to the micropyle, c) hemispherical deposists of cutin on the anticlinal walls of the endotegmen, and c) a thin layer of endosperm that covers the radicle. During its cellular stage of development, the endosperm has conspicuous transfer walls at the chalazal end next to the nucella. The embryo is small and has a conical cotyledon.

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Revisiting the source of wilt symptoms: X-ray microcomputed tomography provides direct evidence that Ralstonia biomass clogs xylem vessels

10.1101/2021.03.19.436187 ◽

2021 ◽

Author(s):

Brian Ingel ◽

Denise Caldwell ◽

Fiona Duong ◽

Dilworth Y. Parkinson ◽

Katherine A. McCulloh ◽

...

Keyword(s):

Stomatal Conductance ◽

Light Microscopy ◽

Bacterial Wilt ◽

Xylem Sap ◽

Physiological Mechanism ◽

Bacterial Biomass ◽

Microcomputed Tomography ◽

Wilt Disease ◽

X Ray ◽

Bacterial Wilt Disease

AbstractPlant pathogenic Ralstonia cause wilt diseases by colonizing xylem vessels and disrupting water transport. Due to the abundance of Ralstonia cells in vessels, the dogma is that bacterial biomass clogs vessels and reduces the flow of xylem sap. However, the physiological mechanism of xylem disruption during bacterial wilt disease is untested. Using a tomato and Ralstonia pseudosolanacearum GMI1000 model, we visualized and quantified the spatiotemporal dynamics of xylem disruption during bacterial wilt disease. First, we measured stomatal conductance of leaflets on mock-inoculated and wilt-symptomatic plants. Wilted leaflets had reduced stomatal conductance, as did turgid leaflets located on the same petiole as wilted leaflets. Next, we used X-ray microcomputed tomography (X-ray microCT) and light microscopy to differentiate between mechanisms of xylem disruption: blockage by bacterial biomass, blockage by vascular tyloses, or sap displacement by gas embolisms. We imaged stems on plants with intact roots and leaves to quantify embolized vessels. Embolized vessels were rare, but there was a slight trend of increased vessel embolisms in infected plants with low bacterial population sizes. To test the hypothesis that vessels are clogged during bacterial wilt, we imaged excised stems after allowing the sap to evaporate during a brief dehydration. Most xylem vessels in mock-infected plants emptied their contents after excision, but non-conductive clogged vessels were abundant in infected plants by 2 days post infection. At wilt onset when bacterial populations exceeded 5×108 cfu/g stem tissue, approximately half of the xylem vessels were clogged with electron-dense bacterial biomass. We found no evidence of tyloses in the X-ray microCT reconstructions or light microscopy on the preserved stems. Bacterial blockage of vessels appears to be the principal cause of vascular disruption during Ralstonia wilt.

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