scholarly journals CO 2 diffusion in tobacco: a link between mesophyll conductance and leaf anatomy

2021 ◽  
Vol 11 (2) ◽  
pp. 20200040
Author(s):  
Victoria C. Clarke ◽  
Florence R. Danila ◽  
Susanne von Caemmerer
Keyword(s):  
Cell Walls ◽  
Leaf Age ◽  
Mesophyll Cell ◽  
Tunable Diode Laser ◽  
Mesophyll Conductance ◽  
Anatomical Changes ◽  
Unit Leaf ◽  
Diode Laser Spectroscopy ◽  
Isotope Measurements

The partial pressure of CO 2 at the sites of carboxylation within chloroplasts depends on the conductance to CO 2 diffusion from intercellular airspace to the sites of carboxylation, termed mesophyll conductance ( g m ). We investigated how g m varies with leaf age and through a tobacco ( Nicotiana tabacum ) canopy by combining gas exchange and carbon isotope measurements using tunable diode laser spectroscopy. We combined these measurements with the anatomical characterization of leaves. CO 2 assimilation rate, A , and g m decreased as leaves aged and moved lower in the canopy and were linearly correlated. This was accompanied by large anatomical changes including an increase in leaf thickness. Chloroplast surface area exposed to the intercellular airspace per unit leaf area ( S c ) also decreased lower in the canopy. Older leaves had thicker mesophyll cell walls and g m was inversely proportional to cell wall thickness. We conclude that reduced g m of older leaves lower in the canopy was associated with a reduction in S c and a thickening of mesophyll cell walls.

Variability in the chloroplast area lining the intercellular airspace and cell walls drives mesophyll conductance in gymnosperms

2020 ◽  
Vol 71 (16) ◽  
pp. 4958-4971 ◽  
Author(s):  
Linda-Liisa Veromann-Jürgenson ◽  
Timothy J Brodribb ◽  
Ülo Niinemets ◽  
Tiina Tosens
Keyword(s):  
Cell Walls ◽  
Mesophyll Cell ◽  
Dry Mass ◽  
Detailed Knowledge ◽  
Mesophyll Conductance ◽  
Phylogenetic Groups ◽  
Leaf Dry Mass ◽  
Component Traits ◽  
Structural Traits ◽  
Distinguishing Features

Abstract The photosynthetic efficiency of plants in different environments is controlled by stomata, hydraulics, biochemistry, and mesophyll conductance (gm). Recently, gm was demonstrated to be the key limitation of photosynthesis in gymnosperms. Values of gm across gymnosperms varied over 20-fold, but this variation was poorly explained by robust structure-bound integrated traits such as leaf dry mass per area. Understanding how the component structural traits control gm is central for identifying the determinants of variability in gm across plant functional and phylogenetic groups. Here, we investigated the structural traits responsible for gm in 65 diverse gymnosperms. Although the integrated morphological traits, shape, and anatomical characteristics varied widely across species, the distinguishing features of all gymnosperms were thick mesophyll cell walls and low chloroplast area exposed to intercellular airspace (Sc/S) compared with angiosperms. Sc/S and cell wall thickness were the fundamental traits driving variations in gm across gymnosperm species. Chloroplast thickness was the strongest limitation of gm among liquid-phase components. The variation in leaf dry mass per area was not correlated with the key ultrastructural traits determining gm. Thus, given the absence of correlating integrated easy-to-measure traits, detailed knowledge of underlying component traits controlling gm across plant taxa is necessary to understand the photosynthetic limitations across ecosystems.

Characterization of machined polystyrene foam

1989 ◽  
Vol 47 ◽  
pp. 372-373
Author(s):  
C. W. Price ◽  
E. F. Lindsey ◽  
R. M. Franks ◽  
M. A. Lane
Keyword(s):  
Surface Finish ◽  
Cell Walls ◽  
Surface Structures ◽  
Efficient Technique ◽  
Low Density ◽  
Polystyrene Foam ◽  
Planar Surfaces ◽  
Machining Characteristics

Diamond-point turning is an efficient technique for machining low-density polystyrene foam, and the surface finish can be substantially improved by grinding. However, both diamond-point turning and grinding tend to tear and fracture cell walls and leave asperities formed by agglomerations of fragmented cell walls. Vibratoming is proving to be an excellent technique to form planar surfaces in polystyrene, and the machining characteristics of vibratoming and diamond-point turning are compared.Our work has demonstrated that proper evaluation of surface structures in low density polystyrene foam requires stereoscopic examinations; tilts of + and − 3 1/2 degrees were used for the stereo pairs. Coating does not seriously distort low-density polystyrene foam. Therefore, the specimens were gold-palladium coated and examined in a Hitachi S-800 FESEM at 5 kV.

Biochemical and Morphological Characterization of Heterotrophic Crypthecodinium cohnii and Chlorella vulgaris Cell Walls

2021 ◽  
Vol 69 (7) ◽  
pp. 2226-2235
Author(s):  
Greta Canelli ◽  
Patricia Murciano Martínez ◽  
Sean Austin ◽  
Mark E. Ambühl ◽  
Fabiola Dionisi ◽  
...  
Keyword(s):  
Chlorella Vulgaris ◽  
Cell Walls ◽  
Morphological Characterization ◽  
Crypthecodinium Cohnii

scholarly journals Characterization of Passage-Selected Vancomycin-Resistant Staphylococcus aureus Strains of Diverse Parental Backgrounds

2000 ◽  
Vol 44 (2) ◽  
pp. 294-303 ◽  
Author(s):  
Richard F. Pfeltz ◽  
Vineet K. Singh ◽  
Jennifer L. Schmidt ◽  
Michael A. Batten ◽  
Christopher S. Baranyk ◽  
...  
Keyword(s):  
Staphylococcus Aureus ◽  
Cell Walls ◽  
Methicillin Resistance ◽  
Surface Hydrophobicity ◽  
Whole Cell ◽  
Transmission Electron ◽  
Vancomycin Mics ◽  
Vancomycin Resistant ◽  
Doubling Times

ABSTRACT A series of 12 Staphylococcus aureus strains of various genetic backgrounds, methicillin resistance levels, and autolytic activities were subjected to selection for the glycopeptide-intermediate S. aureus (GISA) susceptibility phenotype on increasing concentrations of vancomycin. Six strains acquired the phenotype rapidly, two did so slowly, and four failed to do so. The vancomycin MICs for the GISA strains ranged from 4 to 16 μg/ml, were stable to 20 nonselective passages, and expressed resistance homogeneously. Neither ease of acquisition of the GISA phenotype nor the MIC attained correlated with methicillin resistance hetero- versus homogeneity or autolytic deficiency or sufficiency. Oxacillin MICs were generally unchanged between parent and GISA strains, although the mec members of both isogenic methicillin-susceptible and methicillin-resistant pairs acquired the GISA phenotype more rapidly and to higher MICs than did their susceptible counterparts. Transmission electron microscopy revealed that the GISA strains appeared normal in the absence of vancomycin but had thickened and diffuse cell walls when grown with vancomycin at one-half the MIC. Common features among GISAs were reduced doubling times, decreased lysostaphin susceptibilities, and reduced whole-cell and zymographic autolytic activities in the absence of vancomycin. This, with surface hydrophobicity differences, indicated that even in the absence of vancomycin the GISA cell walls differed from those of the parents. Autolytic activities were further reduced by the inclusion of vancomycin in whole-cell and zymographic studies. The six least vancomycin-susceptible GISA strains exhibited an increased capacity to remove vancomycin from the medium versus their parent lines. This study suggests that while some elements of the GISA phenotype are strain specific, many are common to the phenotype although their expression is influenced by genetic background. GISA strains with similar glycopeptide MICs may express individual components of the phenotype to different extents.

Measurements of CH 4 and N 2 O fluxes at the landscape scale using micrometeorological methods

1995 ◽  
Vol 351 (1696) ◽  
pp. 339-356 ◽  
Keyword(s):  
Eddy Covariance ◽  
Arable Land ◽  
Temperature Response ◽  
Mean Value ◽  
Tunable Diode Laser ◽  
Hudson Bay ◽  
Flux Footprint ◽  
Relaxed Eddy Accumulation ◽  
Diode Laser Spectroscopy ◽  
Emission Fluxes

Flux gradient, eddy covariance and relaxed eddy accumulation methods were applied to measure CH 4 and N 2 O emissions from peatlands and arable land respectively. Measurements of N 2 O emission by eddy covariance using tunable diode laser spectroscopy provided fluxes ranging from 2 to 60 µ mol N 2 O m -2 h -1 with a mean value of 22 µ mol N 2 O m -2 h -1 from 320 h of continuous measurements. Fluxes of CH 4 measured above peatland in Caithness (U.K.) during May and June 1993 by eddy covariance and relaxed eddy accumulation methods were in the range 70 to 120 µ mol CH 4 m -2 h -1 with means of 14.7 µ mol CH 4 m -2 h -1 and 22.7 µ mol CH 4 m -2 h -1 respectively. Emissions of CH 4 from peatland changed with water table depth and soil temperature; increasing from 25 |Amol CH 4 m -2 h -1 at 5% pool area to 50 p.mol CH 4 m -2 h -1 with 30% within the flux footprint occupied by pools. A temperature response of 4.9 (xmol CH 4 m -2 h -1 °C -1 in the range 6-12 °C was also observed. The close similarity in average CH 4 emission fluxes reported for wetlands in Caithness, Hudson Bay and Alaska in the range 11 to 40 jamol CH 4 m -2 h -1 suggests that earlier estimates of CH 4 emission from high latitude wetlands were too large or that the area of high latitudes contributing to CH 4 emission has been seriously underestimated.

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