scholarly journals Alleviation of Al toxicity by Si is associated with the formation of Al-Si complexes in root tissues of sorghum

2017 ◽  
Author(s):  
Peter M. Kopittke ◽  
Alessandra Gianoncelli ◽  
George Kourousias ◽  
Kathryn Green ◽  
Brigid A. McKenna
Keyword(s):  
Cross Sections ◽  
Root Elongation ◽  
Elongation Rate ◽  
In Planta ◽  
X Ray ◽  
Root Elongation Rate ◽  
Root Tissues ◽  
Wall Loosening ◽  
Nutrient Solutions

AbstractSilicon is reported to reduce the toxic effects of Al on root elongation but the in planta mechanism by which this occurs remains unclear. Using seedlings of soybean (Glycine max) and sorghum (Sorghum bicolor), we examined the effect of up to 2 mM Si on root elongation rate (RER) in Al-toxic nutrient solutions. Synchrotron-based low energy X-ray fluorescence (LEXRF) was then used for the in situ examination of the distribution of Al and Si within cross-sections cut from the apical tissues of sorghum roots. The addition of Si potentially increased RER in Al-toxic solutions, with RER being up to ca. 0.3 mm h−1 (14 %) higher for soybean and ca. 0.2 mm h−1 (17 %) higher for sorghum relative to solutions without added Si. This improvement in RER could not be attributed to a change in Al-chemistry of the bulk nutrient solution, nor was it due to a change in the concentration of Al within the apical (0-10 mm) root tissues. Using LEXRF to examine sorghum, it was demonstrated that in roots exposed to both Al and Si, much of the Al was co-located with Si in the mucigel and outer apoplast. These observations suggest that Si reduces the toxicity of Al in planta through formation of Al-Si complexes in mucigel and outer cellular tissues, thereby decreasing the binding of Al to the cell wall where it is known to inhibit wall loosening as required for cell elongation.

Primary Root Elongation Rate and Abscisic Acid Levels of Maize in Response to Water Stress

Crop Science ◽  
2011 ◽  
Vol 51 (1) ◽  
pp. 157-172 ◽  
Author(s):  
Kristen A. Leach ◽  
Lindsey G. Hejlek ◽  
Leonard B. Hearne ◽  
Henry T. Nguyen ◽  
Robert E. Sharp ◽  
...  
Keyword(s):  
Abscisic Acid ◽  
Water Stress ◽  
Root Elongation ◽  
Primary Root ◽  
Elongation Rate ◽  
Root Elongation Rate ◽  
Response To Water

scholarly journals Study of Mural Paintings Using In Situ XRF, Confocal Synchrotron-μ-XRF, μ-XRD, Optical Microscopy, and SEM-EDS—The Case of the Frescoes from Misericordia Church of Odemira

2011 ◽  
Vol 17 (5) ◽  
pp. 702-709 ◽  
Author(s):  
S. Valadas ◽  
A. Candeias ◽  
J. Mirão ◽  
D. Tavares ◽  
J. Coroado ◽  
...  
Keyword(s):  
Optical Microscopy ◽  
Cross Sections ◽  
Fluorescence Spectrometry ◽  
Pigment Identification ◽  
X Ray ◽  
Color Changes ◽  
Spatially Resolved ◽  
Mural Paintings ◽  
Different Color

AbstractIn this work, we present the results of an analytical method developed for detailed pigment identification, stratigraphy, and degradation of the paint layers of mural paintings applied in the study of the 17th century frescoes from the Misericordia Church of Odemira (Southwest Portugal). In situ X-ray fluorescence spectrometry analyses were performed on three panels of the mural paintings and complemented by colorimetric measurements. The different color areas were also sampled as microfragments (approx. 1 mm2) that were studied as taken or mounted in epoxy resin to expose the different paint layers. The microfragments of paint layers and their cross sections were characterized by optical microscopy and scanning electron microscopy coupled with energy dispersive X-ray spectrometry. Furthermore, elemental analysis was obtained with spatially resolved confocal synchrotron radiation μ-X-ray fluorescence spectrometry performed at ANKA synchrotron FLUO beamline. Occasionally, phase analysis by μ-X-ray diffraction was also performed. Results from the different techniques allowed pigment identification and, in some cases, the evaluation of color changes due to degradation processes and, considering the Southern Portugal geology, the identification of their possible provenance. The pigments used were essentially yellow, brown and red ochres, smalt blue, copper green, and black earths, probably from local sources.

Measurement of L X-ray production cross sections and relative intensities of some lanthanide compounds depending on the temperature

2020 ◽  
Vol 108 (5) ◽  
pp. 415-423
Author(s):  
Esra Cinan ◽  
Bünyamin Aygün ◽  
M. I. Sayyed ◽  
Yüksel Özdemir
Keyword(s):  
Cross Sections ◽  
Full Width Half Maximum ◽  
Production Cross ◽  
Emission Spectra ◽  
X Rays ◽  
X Ray ◽  
Different Temperatures ◽  
Intensity Ratios ◽  
Annular Source

AbstractL X-ray intensity ratios for CeO2, Sm2(SO4)3, Ho2O3, and Yb2O3 compounds were experimentally investigated. The measurements were gauged following excitation by 59.54 keV γ-rays from a 100 mCi 241Am radioactive annular source at different temperatures in situ. Temperature change occurred between 50 °C and 400 °C. L X-ray emission spectra were obtained by using a solid-state Si(Li) X-ray detector. L X-ray production cross sections, intensity ratios, and full-width half maximum (FWHM) values for the compounds were determined by evaluating the emission spectra varying with the temperature. According to the results obtained, it was observed that Lβ1 X-rays were less influenced in comparison with Lα X-rays while Lα X-rays were also less influenced in comparison with Lβ2 X-rays.

scholarly journals Influence of Day and Night Temperature Differentials on Root Elongation Rate, Root Hydraulic Properties, and Shoot Water Relations in Chrysanthemum

2000 ◽  
Vol 125 (3) ◽  
pp. 383-389
Author(s):  
Pauline Helen Kaufmann ◽  
Robert J. Joly ◽  
P. Allen Hammer
Keyword(s):  
Root Elongation ◽  
Dark Period ◽  
Stem Elongation ◽  
Elongation Rate ◽  
Light Period ◽  
Night Temperature ◽  
Diurnal Patterns ◽  
Root Elongation Rate ◽  
Temperature Regimes ◽  
Maximum Root

The difference between night and day temperature (DIF = day - night temperature) has been shown to affect plant height. A positive DIF (+DIF), cooler night than day temperature, increases stem elongation while a negative DIF (- DIF), warmer night than day temperature, decreases stem elongation. The physiological mechanism underlying the growth response to DIF is not understood, however, and the effects of day/night temperature differentials on root permeability to water and root elongation rate have not been studied. The objective of this study was to describe how +DIF and -DIF temperature regimes affect leaf water relations, root water flux (Jv), root hydraulic conductivity (Lp), and root elongation rates of `Boaldi' chrysanthemum [Dendranthema ×grandiflora Kitam. `Boaldi' (syn. Chrysanthemum ×morifolium Ramat.)] plants over time. Leaf turgor pressure (ψp) was 0.1 to 0.2 MPa higher in plants grown in a +6 °C DIF environment throughout both the light and dark periods, relative to those in a -6 °C DIF environment. Jv differed markedly in roots of plants grown in +DIF vs. -DIF environments. Rhythmic diurnal patterns of Jv were observed in all DIF treatments, but the relative timing of flux minima and maxima differed among treatments. Plants grown in positive DIF regimes exhibited maximum root flux at the beginning of the light period, while those in negative DIF environments had maximum root flux during the first few hours of the dark period. Plants grown in +DIF had significantly higher Lp than -DIF plants. Plants grown in +DIF and -DIF environments showed differences in the diurnal rhythm of root elongation. During the dark period, +DIF plants exhibited minimal root elongation rates, while -DIF plants exhibited maximal rates. During the light period, the converse was observed. In -DIF temperature regimes, periods of rapid root elongation coincided with periods of high Jv. Results of this study suggest that negative DIF environments lead to leaf turgor reductions and markedly alter diurnal patterns of root elongation. These changes may, in turn, act to reduce stem elongation.

scholarly journals Minimizing experimental artefacts in synchrotron-based X-ray analyses of Fe speciation in tissues of rice plants

2019 ◽  
Vol 26 (4) ◽  
pp. 1272-1279 ◽  
Author(s):  
Peng Wang ◽  
Brigid A. McKenna ◽  
Neal W. Menzies ◽  
Cui Li ◽  
Chris J. Glover ◽  
...  
Keyword(s):  
Freeze Drying ◽  
Plant Root ◽  
Experimental Conditions ◽  
X Ray ◽  
Freeze Dried ◽  
Fe Speciation ◽  
Root Tissues ◽  
X Ray Absorption ◽  
Beam Damage

Iron (Fe) plays an important role within environmental systems. Synchrotron-based X-ray approaches, including X-ray absorption spectroscopy (XAS), provide powerful tools for in situ analyses of Fe speciation, but beam damage during analysis may alter Fe speciation during its measurement. XAS was used to examine whether experimental conditions affect the analysis of Fe speciation in plant tissues. Even when analyzed in a cryostat at 12 K, it was found that FeIII can rapidly (within 0.5–1 min) photoreduce to FeII, although the magnitude of photoreduction varied depending upon the hydration of the sample, the coordination chemistry of the Fe, as well as other properties. For example, photoreduction of FeIII was considerably higher for aqueous standard compounds than for hydrated plant-root tissues. The use of freeze-dried samples in the cryostat (12 K) markedly reduced the magnitude of this FeIII photoreduction, and there was no evidence that the freeze-drying process itself resulted in experimental artefacts under the current experimental conditions, such as through the oxidation of FeII, although some comparatively small differences were observed when comparing spectra of hydrated and freeze-dried FeII compounds. The results of this study have demonstrated that FeIII photoreduction can occur during X-ray analysis, and provides suitable conditions to preserve Fe speciation to minimize the extent of beam damage when analyzing environmental samples. All studies utilizing XAS are encouraged to include a preliminary experiment to determine if beam damage is occurring, and, where appropriate, to take the necessary steps (such as freeze drying) to overcome these issues.

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