Elemental storage in Cucurbita embryos: X-ray microanalysis of magnesium, potassium, calcium, and phosphorus within globoid crystals

1990 ◽  
Vol 68 (3) ◽  
pp. 646-650 ◽  
Author(s):  
I. Ockenden ◽  
J. N. A. Lott
Keyword(s):  
Neutron Activation Analysis ◽  
Electron Microscope ◽  
Activation Analysis ◽  
Cucurbita Maxima ◽  
Mesophyll Cells ◽  
X Ray ◽  
Reciprocal Hybrids ◽  
Calcium And Phosphorus ◽  
Total Concentrations ◽  
Scanning Electron

Embryos of Cucurbita maxima, Cucurbita andreana, and their reciprocal hybrids store phosphorus, magnesium, potassium, and calcium in distinctive globoid crystals within protein bodies found in cotyledon mesophyll cells. Samples of cotyledon tissue from each of the four kinds of embryos were cryogenically prepared and analyzed by X-ray microanalysis in the frozen state in a scanning electron microscope. The relative proportions of phosphorus, magnesium, potassium, and calcium were expressed as peak to background ratios. Total concentrations of the four elements in whole cotyledons, as measured by neutron activation analysis, were similar to the trends shown by the peak to background ratios for the same elements. This supports the concept that the bulk of the elements P, K, Mg, and Ca in seed tissues is stored in globoid crystals.

Magnetic spherules from Recent fluvial sediments in Alberta, Canada: characteristics and possible origins

1995 ◽  
Vol 32 (4) ◽  
pp. 351-358 ◽  
Author(s):  
Dong Bi ◽  
Roger D. Morton
Keyword(s):  
Neutron Activation Analysis ◽  
Electron Microscope ◽  
Activation Analysis ◽  
Neutron Activation ◽  
Fluvial Sediments ◽  
X Ray Diffraction ◽  
X Ray ◽  
Iron Metal ◽  
Extraterrestrial Origin ◽  
Scanning Electron

Magnetic spherules were recently recovered in recent fluvial sediments in Alberta, Canada, and have been studied using X-ray diffraction, electron microprobe, scanning electron microscope, and neutron activation analysis. Results show that these spherules are composed of magnetite, wüstite, and hematite; some of them contain α-iron metal cores. The similarities in morphology, mineralogy, and internal structure of these spherules to spherules of extraterrestrial origin found in other environments suggest that some of these spherules from Alberta might also be of extraterrestrial origin, in spite of their unusual compositions.

Identification of the sites of K leakage from imbibing seeds and grains

1993 ◽  
Vol 3 (2) ◽  
pp. 105-110 ◽  
Author(s):  
Penny Beecroft ◽  
John N. A. Lott
Keyword(s):  
Zea Mays ◽  
Neutron Activation Analysis ◽  
Glycine Max ◽  
Activation Analysis ◽  
Cucurbita Maxima ◽  
Entire Surface ◽  
X Ray ◽  
Freeze Dried ◽  
Pea Seeds ◽  
Potassium Leakage

AbstractSeeds/grains of four species were imbibed for up to 90 minutes half embedded in agar. The agar was then freeze-dried and treated with a chromatographic reagent to detect the sites of potassium leakage from the imbibing seeds/grains. Soybean (Glycine max cv. Marathon) and pea (Pisum sativum cv. Little Marvel) leaked K across the entire surface of their testas. Aged pea seeds leaked much more extensively than seeds of a fresher lot of the same cultivar. Squash (Cucurbita maxima cv. Warted Hubbard) seeds leaked extensively from the flat sides of the seeds and at the hilum, but only slightly at the margins. Maize (Zea mays cv. Golden Beauty) leaked most extensively across the endosperm-only side (i.e. the side opposite the embryo) of the kernel, and kernels leaked more at the tip-cap end than at the broad end. Energy dispersive X-ray analysis determined that K was present in the testas/pericarps before imbibition in all species studied, and that the peak-to-background ratios of K were lower after the seeds/grains had been exposed to water. Neutron activation analysis verified that K was leaked out of the seeds/grains and absorbed into the agar. Seeds from all species studied showed varying amounts of seed-to-seed variation. These variations can be attributed in part to differences in testa/pericarp structure and condition.

Cell walls in Cucurbita maxima cotyledons in relation to imbibition

1974 ◽  
Vol 52 (7) ◽  
pp. 1465-1468 ◽  
Author(s):  
John N. A. Lott
Keyword(s):  
Electron Microscope ◽  
Scanning Electron Microscope ◽  
Electron Micrographs ◽  
Propylene Oxide ◽  
Cell Walls ◽  
Scanning Electron Micrographs ◽  
Cucurbita Maxima ◽  
Glutaraldehyde Fixation ◽  
Mesophyll Cells ◽  
Scanning Electron

The scanning electron microscope and the freeze-etch technique were used to demonstrate the presence of corrugated cell walls in cotyledon mesophyll cells from dry squash seeds. These wavy cell walls straightened out during imbibition. In the scanning electron micrographs no wavy cell walls were observed in the smaller epidermal cells. Tissue imbibed for 2 h and then air-dried contained corrugated cell walls, whereas similar imbibed tissue dehydrated in ethanol and propylene oxide contained smooth cell walls. Thus the method of seed dehydration is important in determining the appearance of wavy cell walls. Glutaraldehyde fixation during the 2-h imbibition process did not alter the conditions under which wavy cell walls reappear.

Mineral analyses of storage reserves of Cucurbita maxima and Cucurbita andreana pollen

1992 ◽  
Vol 70 (3) ◽  
pp. 491-495 ◽  
Author(s):  
Hilary R. Skilnyk ◽  
John N. A. Lott
Keyword(s):  
Neutron Activation Analysis ◽  
Activation Analysis ◽  
Neutron Activation ◽  
Energy Dispersive ◽  
Specimen Preparation ◽  
Cucurbita Maxima ◽  
X Ray ◽  
Thin Sectioning ◽  
Major Loss ◽  
Storage Reserves

Cucurbita maxima and Cucurbita andreana are so closely related that hybridization is possible. These two species also have been shown to have very different levels of calcium storage in their seeds. Our neutron activation analysis studies have shown that the total amount of P, Ca, K, and Mg in pollen of the two species was similar. Energy dispersive X-ray analysis studies also showed that the composition of electron-dense particles in the tube cells of the two species was similar. Thus the differences in Ca levels in phytate reserves in the seeds of these two Cucurbita species do not appear to be paralleled by differences in mineral reserves in the pollen of the two species. Specimen preparation studies demonstrated that even though elements such as P, K, Mg, and Ca are mostly retained by an anhydrous fixation and embedding protocol, thin-sectioning of such blocks on a water-filled microtome boat resulted in major loss of elements. Key words: pollen, mineral nutrients, energy dispersive X-ray analysis, neutron activation analysis, phytate, Cucurbita.

X-ray micro tomography in the scanning electron microscope

1978 ◽  
Vol 36 (1) ◽  
pp. 106-107 ◽  
Author(s):  
W. Brünger
Keyword(s):  
Electron Beam ◽  
Electron Microscope ◽  
Scanning Electron Microscope ◽  
Target Surface ◽  
The Body ◽  
X Rays ◽  
Cross Sectional ◽  
X Ray ◽  
Micro Tomography ◽  
Scanning Electron

Reconstructive tomography is a new technique in diagnostic radiology for imaging cross-sectional planes of the human body /1/. A collimated beam of X-rays is scanned through a thin slice of the body and the transmitted intensity is recorded by a detector giving a linear shadow graph or projection (see fig. 1). Many of these projections at different angles are used to reconstruct the body-layer, usually with the aid of a computer. The picture element size of present tomographic scanners is approximately 1.1 mm2.Micro tomography can be realized using the very fine X-ray source generated by the focused electron beam of a scanning electron microscope (see fig. 2). The translation of the X-ray source is done by a line scan of the electron beam on a polished target surface /2/. Projections at different angles are produced by rotating the object.During the registration of a single scan the electron beam is deflected in one direction only, while both deflections are operating in the display tube.

PHAX-SCAN: Functional integration of a Scanning Electron Microscope and an energy-dispersive x-ray analyser

1989 ◽  
Vol 47 ◽  
pp. 56-57
Author(s):  
Marc H. Peeters ◽  
Max T. Otten
Keyword(s):  
Electron Microscope ◽  
Scanning Electron Microscope ◽  
High Speed ◽  
High Performance ◽  
Functional Integration ◽  
Energy Dispersive ◽  
X Rays ◽  
X Ray ◽  
High Speed Analysis ◽  
Scanning Electron

Over the past decades, the combination of energy-dispersive analysis of X-rays and scanning electron microscopy has proved to be a powerful tool for fast and reliable elemental characterization of a large variety of specimens. The technique has evolved rapidly from a purely qualitative characterization method to a reliable quantitative way of analysis. In the last 5 years, an increasing need for automation is observed, whereby energy-dispersive analysers control the beam and stage movement of the scanning electron microscope in order to collect digital X-ray images and perform unattended point analysis over multiple locations.The Philips High-speed Analysis of X-rays system (PHAX-Scan) makes use of the high performance dual-processor structure of the EDAX PV9900 analyser and the databus structure of the Philips series 500 scanning electron microscope to provide a highly automated, user-friendly and extremely fast microanalysis system. The software that runs on the hardware described above was specifically designed to provide the ultimate attainable speed on the system.

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