scholarly journals Cell-level anatomical characteristics explain high mesophyll conductance and photosynthetic capacity in sclerophyllous Mediterranean oaks

2017 ◽  
Vol 214 (2) ◽  
pp. 585-596 ◽  
Author(s):  
José Javier Peguero-Pina ◽  
Sergio Sisó ◽  
Jaume Flexas ◽  
Jeroni Galmés ◽  
Ana García-Nogales ◽  
...  
Keyword(s):  
Photosynthetic Capacity ◽  
Mesophyll Conductance ◽  
Cell Level ◽  
Anatomical Characteristics ◽  
Mediterranean Oaks

Seasonal analysis of photosynthetic limitations in mature Scots pine trees reveals that models based on intracellular CO2 concentration grossly underestimate photosynthetic capacity

2020 ◽  
Author(s):  
Zsofia R. Stangl ◽  
Lasse Tarvainen ◽  
Mats Räntfors ◽  
Göran Wallin ◽  
John D. Marshall
Keyword(s):  
Scots Pine ◽  
Large Scale ◽  
Photosynthetic Capacity ◽  
Co2 Concentration ◽  
Mesophyll Conductance ◽  
Natural Conditions ◽  
Underlying Assumption ◽  
Relative Contribution ◽  
Pine Trees ◽  
Seasonal Analysis

<p><span>Global models of photosynthesis commonly use photosynthetic capacity parameters (V<sub>cmax</sub>, J<sub>max</sub>) that are estimated based on C<sub>i</sub>, the intercellular CO<sub>2</sub> concentration. The underlying assumption of these models is that mesophyll conductance (gm) is infinite and therefore the CO<sub>2</sub> concentration at the site of carboxylation (C<sub>c</sub>) is equal to C<sub>i</sub>, despite a growing body of literature acknowledging that these assumptions are incorrect. Because relatively few studies on gm have been conducted under natural conditions and with high enough resolution, it is currently unclear how significant the assumption of infinite C<sub>c</sub> is for the accuracy of long-term predictions by large-scale photosynthesis models. In this study we investigated this question with data collected in a mature Scots pine stand, one of the dominant species of the boreal region. We conducted high-resolution gas-exchange and online <sup>13</sup>C discrimination measurements over a whole growing season (May-October), and analysed the relative contribution of diffusional and biochemical limitations to photosynthesis. We hypothesised that diffusional limitation will be significant in this species, as conifers typically have low stomatal and mesophyll conductance (g<sub>s</sub> and g<sub>m</sub> respectively). Accordingly, we found that diffusional limitations were similar or stronger than biochemical limitation during May-July, and that all limitations reached minima around the end of June when A<sub>net</sub> values were highest. However, during August-October biochemical limitation became increasingly dominant, as the diffusional limitations were relatively small and stable. Over the whole period, both g<sub>m</sub> and the relative mesophyll limitation were similar in magnitude to g<sub>s</sub> and the stomatal limitation, respectively, resulting in a 40-100 ppm reduction in CO2 concentration between C<sub>i</sub> and C<sub>c</sub>. This meant that V<sub>cmax</sub> was under-estimated by 20-40% when calculated from C<sub>i</sub>compared to C<sub>c</sub>, highlighting the importance of accounting for the finite g<sub>m </sub>when determining photosynthetic capacity and modelling photosynthesis under natural conditions.</span></p>

Systematic zone-Axis orientation of NM-scale particles for microdiffraction

1990 ◽  
Vol 48 (4) ◽  
pp. 262-263
Author(s):  
E D Boyes ◽  
L Hanna
Keyword(s):  
Real Space ◽  
Dark Field ◽  
Zone Axis ◽  
High Symmetry ◽  
Lattice Imaging ◽  
Cell Level ◽  
Bright Field ◽  
Axis Orientation ◽  
Annular Dark Field ◽  
Target Designation

A VG HB501 FEG STEM has been modified to provide track whilst tilt [TWIT] facilities for controllably tilting selected and initially randomly aligned nanometer-sized particles into the high symmetry zone-axis orientations required for microdiffraction, lattice imaging and chemical microanalysis at the unit cell level. New electronics display in alternate TV fields and effectively in parallel on split [+VTR] or adjacent externally synchronized screens, the micro-diffraction pattern from a selected area down to <1nm2 in size, together with the bright field and high angle annular dark field [HADF] STEM images of a much wider [˜1μm] area centered on the same spot. The new system makes it possible to tilt each selected and initially randomly aligned small particle into a zone axis orientation for microdiffraction, or away from it to minimize orientation effects in chemical microanalysis. Tracking of the inevitable specimen movement with tilt is controlled by the operator, with realtime [60Hz] update of the target designation in real space and the diffraction data in reciprocal space. The spot mode micro-DP and images of the surrounding area are displayed continuously. The regular motorized goniometer stage for the HB501STEM is a top entry design but the new control facilities are almost equivalent to having a stage which is eucentric with nanometric precision about both tilt axes.

Mesophyll conductance: the leaf corridors for photosynthesis

2020 ◽  
Vol 48 (2) ◽  
pp. 429-439 ◽  
Author(s):  
Jorge Gago ◽  
Danilo M. Daloso ◽  
Marc Carriquí ◽  
Miquel Nadal ◽  
Melanie Morales ◽  
...  
Keyword(s):  
Molecular Mechanisms ◽  
Current Knowledge ◽  
Main Role ◽  
Mesophyll Conductance ◽  
Future Studies ◽  
Cell Structures ◽  
Leaf Tissues ◽  
Change Framework ◽  
Chloroplast Stroma

Besides stomata, the photosynthetic CO2 pathway also involves the transport of CO2 from the sub-stomatal air spaces inside to the carboxylation sites in the chloroplast stroma, where Rubisco is located. This pathway is far to be a simple and direct way, formed by series of consecutive barriers that the CO2 should cross to be finally assimilated in photosynthesis, known as the mesophyll conductance (gm). Therefore, the gm reflects the pathway through different air, water and biophysical barriers within the leaf tissues and cell structures. Currently, it is known that gm can impose the same level of limitation (or even higher depending of the conditions) to photosynthesis than the wider known stomata or biochemistry. In this mini-review, we are focused on each of the gm determinants to summarize the current knowledge on the mechanisms driving gm from anatomical to metabolic and biochemical perspectives. Special attention deserve the latest studies demonstrating the importance of the molecular mechanisms driving anatomical traits as cell wall and the chloroplast surface exposed to the mesophyll airspaces (Sc/S) that significantly constrain gm. However, even considering these recent discoveries, still is poorly understood the mechanisms about signaling pathways linking the environment a/biotic stressors with gm responses. Thus, considering the main role of gm as a major driver of the CO2 availability at the carboxylation sites, future studies into these aspects will help us to understand photosynthesis responses in a global change framework.

Changes in growth and photosynthetic capacity of rice with increased UV-B radiation

1991 ◽  
Vol 83 (3) ◽  
pp. 373-380 ◽  
Author(s):  
Alan H. Teramura ◽  
Lewis H. Ziska ◽  
A. Ester Sztein
Keyword(s):  
Photosynthetic Capacity

Influence of anatomy on the adhesion performance of four wood species

2020 ◽  
Vol 9 (4) ◽  
pp. e31942727
Author(s):  
João Gabriel Missia da Silva ◽  
Pedro Nicó de Medeiros ◽  
Denise Ransolin Soranso ◽  
Vinicius Peixoto Tinti ◽  
José Tarcísio da Silva Oliveira ◽  
...  
Keyword(s):  
Shear Strength ◽  
Specific Gravity ◽  
Wood Species ◽  
Tectona Grandis ◽  
Glue Line ◽  
Anatomical Characteristics ◽  
Ray Cells ◽  
Adhesion Performance ◽  
Adhesion Process

The aim of this study was to evaluate the influence of anatomical characteristics on the adhesion performance of Vatairea sp., Paulownia sp., Aspidosperma populifolium and Tectona grandis wood. Specimens for anatomical, physical and mechanical analyzes were produced from tangentially oriented boards. The treatments were joint glued from pieces of the same anatomical orientation (radial and tangential), evaluated for shear strength and glue line failure. The Vatairea sp wood had the highest specific gravity (0.74 g cm-3) and the Paulownia sp (0.34 g cm-3) wood was smaller. Aspidosperma populifolium species showed the highest shear strength in the glue line in the tangential and radial faces. The anatomical variables with higher influence on the wood adhesion process were pith ray cells and especially fibers that exhibit the greatest correlation with the shear strength of the glue line.

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