scholarly journals The Effect of Leaf-Level Spatial Variability in Photosynthetic Capacity on Biochemical Parameter Estimates Using the Farquhar Model: A Theoretical Analysis

2008 ◽  
Vol 148 (2) ◽  
pp. 1139-1147 ◽  
Author(s):  
Charles P. Chen ◽  
Xin-Guang Zhu ◽  
Stephen P. Long
2018 ◽  
Vol 38 (12) ◽  
pp. 1926-1926
Author(s):  
Agne Gvozdevaite ◽  
Imma Oliveras ◽  
Tomas Ferreira Domingues ◽  
Theresa Peprah ◽  
Mickey Boakye ◽  
...  

2021 ◽  
Author(s):  
Ning Dong ◽  
Iain Colin Prentice ◽  
Ian Wright ◽  
Xiangzhong Luo ◽  
Nick Smith

<div> <p>Nitrogen (N) limitation constrains the magnitude of terrestrial carbon uptake in response to CO<sub>2 </sub>fertilization and climate change. However, the trajectory of N demand, and how it is influenced by continuing changes in CO<sub>2 </sub>and climate, is incompletely understood. We estimate recent changes in global canopy N demand based on a well-tested optimality hypothesis for the control of photosynthetic capacity (<em>V</em><sub>cmax</sub>). The predicted global pattern of optimal leaf-level <em>V</em><sub>cmax </sub>is similar to the pattern derived from remotely sensed chlorophyll retrievals. Over the period from 1982 to 2015, rising CO<sub>2­ </sub>and warming both contributed to decreasing leaf-level N demand. Widespread increases in green vegetation cover over the same period (especially in high latitudes) imply increasing total canopy N demand. The net global trend is, nonetheless, a decrease in total canopy N demand. This work provides a new perspective on the past, present and future of the global terrestrial N cycle.</p> </div>


Plants ◽  
2020 ◽  
Vol 9 (9) ◽  
pp. 1091
Author(s):  
Víctor Resco de Dios ◽  
William R.L. Anderegg ◽  
Ximeng Li ◽  
David T. Tissue ◽  
Michael Bahn ◽  
...  

The circadian clock is a molecular timer of metabolism that affects the diurnal pattern of stomatal conductance (gs), amongst other processes, in a broad array of plant species. The function of circadian gs regulation remains unknown and here, we test whether circadian regulation helps to optimize diurnal variations in stomatal conductance. We subjected bean (Phaseolus vulgaris) and cotton (Gossypium hirsutum) canopies to fixed, continuous environmental conditions of photosynthetically active radiation, temperature, and vapour pressure deficit (free-running conditions) over 48 h. We modelled gs variations in free-running conditions to test for two possible optimizations of stomatal behaviour under circadian regulation: (i) that stomata operate to maintain constant marginal water use efficiency; or (ii) that stomata maximize C net gain minus the costs or risks of hydraulic damage. We observed that both optimization models predicted gs poorly under free-running conditions, indicating that circadian regulation does not directly lead to stomatal optimization. We also demonstrate that failure to account for circadian variation in gs could potentially lead to biased parameter estimates during calibrations of stomatal models. More broadly, our results add to the emerging field of plant circadian ecology, where circadian controls may partially explain leaf-level patterns observed in the field.


2021 ◽  
Vol 21 (1) ◽  
Author(s):  
Jaameeta Kurji ◽  
Charles Thickstun ◽  
Gebeyehu Bulcha ◽  
Monica Taljaard ◽  
Ziqi Li ◽  
...  

Abstract Background Persisting within-country disparities in maternal health service access are significant barriers to attaining the Sustainable Development Goals aimed at reducing inequalities and ensuring good health for all. Sub-national decision-makers mandated to deliver health services play a central role in advancing equity but require appropriate evidence to craft effective responses. We use spatial analyses to identify locally-relevant barriers to access using sub-national data from rural areas in Jimma Zone, Ethiopia. Methods Cross-sectional data from 3727 households, in three districts, collected at baseline in a cluster randomized controlled trial were analysed using geographically-weighted regressions. These models help to quantify associations within women’s proximal contexts by generating local parameter estimates. Data subsets, representing an empirically-identified scale for neighbourhood, were used. Local associations between outcomes (antenatal, delivery, and postnatal care use) and potential explanatory factors at individual-level (ex: health information source), interpersonal-level (ex: companion support availability) and health service-levels (ex: nearby health facility type) were modelled. Statistically significant local odds ratios were mapped to demonstrate how relevance and magnitude of associations between various explanatory factors and service outcomes change depending on locality. Results Significant spatial variability in relationships between all services and their explanatory factors (p < 0.001) was detected, apart from the association between delivery care and women’s decision-making involvement (p = 0.124). Local models helped to pinpoint factors, such as danger sign awareness, that were relevant for some localities but not others. Among factors with more widespread influence, such as that of prior service use, variation in estimate magnitudes between localities was uncovered. Prominence of factors also differed between services; companion support, for example, had wider influence for delivery than postnatal care. No significant local associations with postnatal care use were detected for some factors, including wealth and decision involvement, at the selected neighbourhood scale. Conclusions Spatial variability in service use associations means that the relative importance of explanatory factors changes with locality. These differences have important implications for the design of equity-oriented and responsive health systems. Reductions in within-country disparities are also unlikely if uniform solutions are applied to heterogeneous contexts. Multi-scale models, accommodating factor-specific neighbourhood scaling, may help to improve estimated local associations.


2011 ◽  
Vol 48 (4) ◽  
pp. 285-295 ◽  
Author(s):  
A. Abo Al-kheer ◽  
M. Eid ◽  
Y. Aoues ◽  
A. El-Hami ◽  
M.G. Kharmanda ◽  
...  

2016 ◽  
Vol 214 (3) ◽  
pp. 1002-1018 ◽  
Author(s):  
Nur H. A. Bahar ◽  
F. Yoko Ishida ◽  
Lasantha K. Weerasinghe ◽  
Rossella Guerrieri ◽  
Odhran S. O'Sullivan ◽  
...  

HortScience ◽  
1996 ◽  
Vol 31 (4) ◽  
pp. 682a-682
Author(s):  
C. Bellert ◽  
F. Gauthier ◽  
B. Dansereau

The photosynthetic activity of four Rhododendron simsii cultivars `Dorothy Gish', `Paloma', `White Gish', and `Gloria' were studied at both the individual leaf level using a portable photosynthesis system (closed), or at the whole-plant level using assimilation chambers (semi-open system). Net photosynthetic assimilation curves in response to light in both systems will be established. The experimental points obtained will be adjusted to a photosynthetic model as described in the literature. The model parameters [original efficiency (α) dark respiration (Rd), maximum photosynthetic capacity to saturated light (Pmax)] will be presented. The evolution of these parameters will be presented as a function of the various stages of development. Also a comparison of the four cultivars will be shown.


2018 ◽  
Vol 38 (12) ◽  
pp. 1912-1925 ◽  
Author(s):  
Agne Gvozdevaite ◽  
Imma Oliveras ◽  
Tomas Ferreira Domingues ◽  
Theresa Peprah ◽  
Mickey Boakye ◽  
...  

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