Consequences of phloem pathway unloading/reloading on equilibrium flows between source and sink: a modelling approach

2017 ◽  
Vol 44 (5) ◽  
pp. 507 ◽  
Author(s):  
Peter E. H. Minchin ◽  
André Lacointe
Keyword(s):  
Large Fraction ◽  
Phloem Transport ◽  
Solute Concentration ◽  
Sources And Sinks ◽  
Pressure Profiles ◽  
Flow Mechanisms ◽  
Source Sink ◽  
Pressure Driven Flow ◽  
Source And Sink ◽  
Modelling Approach

It is now accepted that the transport phloem, linking major sources and sinks, is leaky, and this leakage can be considerable. Hence for phloem transport to function over the long distances observed, a large fraction of this unloaded photosynthate must be reloaded. A fraction of this unloaded solute is used to maintain tissues surrounding the phloem, as well as being stored. Also, pathway unloading/reloading acts as a short-term buffer to source and sink changes. In this work we present the first attempt to include both pathway unloading and reloading of carbohydrate in the modelling of pressure driven flow to determine if this has any significant effect upon source–sink dynamics. Our results indicated that the flow does not follow Poiseuille dynamics, and that pathway unloading alters the solute concentration and hydrostatic pressure profiles. Hence, measurement of either of these without considerable other detail tells us very little about the flow mechanisms. With adequate reloading along the pathway, the effects of pathway unloading can completely compensate for, making the entire system look like one with no pathway unloading.

scholarly journals Exploring Tradeoffs in Merged Pipeline Infrastructure for Carbon Dioxide Integration Networks

2020 ◽  
Vol 12 (7) ◽  
pp. 2678
Author(s):  
Sabla Y. Alnouri ◽  
Dhabia M. Al-Mohannadi
Keyword(s):  
Cost Savings ◽  
Emission Sources ◽  
Source Pressure ◽  
Modified Model ◽  
Sources And Sinks ◽  
Co2 Transportation ◽  
Merging Techniques ◽  
Carbon Network ◽  
Source And Sink

Carbon integration aims to identify appropriate CO2 capture, allocation, and utilization options, given a number of emission sources and sinks. Numerous CO2-using processes capture and convert emitted CO2 streams into more useful forms. The transportation of captured CO2, which poses a major design challenge, especially across short distances. This paper investigates new CO2 transportation design aspects by introducing pipeline merging techniques into carbon integration network design. For this, several tradeoffs, mainly between compression and pipeline costs, for merged pipeline infrastructure scenarios have been studied. A modified model is introduced and applied in this work. It is found that savings on pipeline costs are greatly affected by compression/pumping levels. A case study using two different pipe merging techniques was applied and tested. Backward branching was reported to yield more cost savings in the resulting carbon network infrastructure. Moreover, both the source and sink pressures were found to greatly impact the overall cost of the carbon integration network attained via merged infrastructure. It was found that compression costs consistently decreased with increasing source pressure, unlike the pumping and pipeline costs.

scholarly journals Microbial feedbacks optimize ocean iron availability

2020 ◽  
Vol 117 (9) ◽  
pp. 4842-4849
Author(s):  
Jonathan Maitland Lauderdale ◽  
Rogier Braakman ◽  
Gaël Forget ◽  
Stephanie Dutkiewicz ◽  
Michael J. Follows
Keyword(s):  
Large Fraction ◽  
Global Scale ◽  
Microbial Production ◽  
Limiting Factor ◽  
Iron Cycling ◽  
Dissolved Iron ◽  
Surface Ocean ◽  
Source Sink ◽  
Model Ocean ◽  
Additional Iron

Iron is the limiting factor for biological production over a large fraction of the surface ocean because free iron is rapidly scavenged or precipitated under aerobic conditions. Standing stocks of dissolved iron are maintained by association with organic molecules (ligands) produced by biological processes. We hypothesize a positive feedback between iron cycling, microbial activity, and ligand abundance: External iron input fuels microbial production, creating organic ligands that support more iron in seawater, leading to further macronutrient consumption until other microbial requirements such as macronutrients or light become limiting, and additional iron no longer increases productivity. This feedback emerges in numerical simulations of the coupled marine cycles of macronutrients and iron that resolve the dynamic microbial production and loss of iron-chelating ligands. The model solutions resemble modern nutrient distributions only over a finite range of prescribed ligand source/sink ratios where the model ocean is driven to global-scale colimitation by micronutrients and macronutrients and global production is maximized. We hypothesize that a global-scale selection for microbial ligand cycling may have occurred to maintain “just enough” iron in the ocean.

scholarly journals Application of Neural Networks for Retrieval of the CO2 Concentration at Aerospace Sensing by IPDA-DIAL lidar

2019 ◽  
Vol 11 (6) ◽  
pp. 659 ◽  
Author(s):  
Gennadii G Matvienko ◽  
and Alexander Ya Sukhanov
Keyword(s):  
Neural Networks ◽  
Co2 Concentration ◽  
Surface Concentration ◽  
Average Concentration ◽  
Differential Absorption ◽  
Near Surface ◽  
Sources And Sinks ◽  
Pressure Profiles ◽  
Temperature And Pressure ◽  
Fully Connected

Greenhouse gas concentrations are increasing over the past few decades, creating the need to measure their concentration with high accuracy, including for determining their trends, sources, and sinks. In this regard, various methods of regional and global control are being developed. One of the measuring methods is passive satellite method, but they allow for you to get data mainly during the day and outside the poles of the Earth. Another method is active lidar; they require the consideration of various aspects that are related to the technical characteristics of the lidar and methods for solving inverse problems. This article discusses the possibility of using lidars for sensing carbon dioxide from space (orbit 450 km) and from a height of 10 km and 23 km, which presumably corresponds to the aircrafts and balloons. As a method of solving the inverse problem, the method of fully connected neural networks with three layers and pre-training of first layer is considered, allowing for the application of additional data, including the IPDA (Integrated Path Differential Absorption) signal, the scattered DIAL (Differential Absorption Lidar) signal, temperature, and pressure profiles. These estimates show the possibility of measuring the average concentration from an orbit height of 450 km with an error of 0.16%, a resolution of 60 km, with a 50 mJ laser pulse energy, and 1 m diameter telescope. It is also shown that it is possible to obtain the concentration profile, including the near-surface concentration with an error of 2 ppm.

scholarly journals Estimating Organ Contribution to Grain Filling and Potential for Source Upregulation in Wheat Cultivars with a Contrasting Source–Sink Balance

Agronomy ◽  
2020 ◽  
Vol 10 (10) ◽  
pp. 1527
Author(s):  
Carolina Rivera-Amado ◽  
Gemma Molero ◽  
Eliseo Trujillo-Negrellos ◽  
Matthew Reynolds ◽  
John Foulkes
Keyword(s):  
Grain Growth ◽  
Photosynthetic Rate ◽  
Grain Filling ◽  
Leaf Sheath ◽  
Grain Weight ◽  
Yield Potential ◽  
Wheat Cultivars ◽  
Sink Limitation ◽  
Source Sink ◽  
Source And Sink

Grain filling may be limited by the joint source and sink capacity in modern wheat cultivars, indicating a need to research the co-limitation of yield by both photosynthesis and the number and potential size of grains. The extent to which the post-anthesis source may be limiting final grain size can be estimated by partial degraining of spikes, while defoliation and shading treatments can be useful to estimate if any excess photosynthetic capacity exists. In the current study, degraining was applied to a set of 26 elite spring wheat cultivars from the International Maize and Wheat Improvement Center (CIMMYT)’s core germplasm (CIMCOG) panel, while lamina defoliation and shading through stem-and-leaf-sheath covering treatments were applied to a subset of the same cultivars. Responses to source treatments in grain weight, pre-anthesis reserve contribution to grain weight, dry-matter translocation efficiency, and flag-leaf and spike photosynthetic rate were measured and compared to an unmanipulated control treatment. Grain weight responses to degraining among cultivars ranged from no response to increases of 28%, suggesting a range of responses from sink limitation, to probable source and sink co-limitation of grain growth. Grain weight’s response to degraining increased linearly with the years of cultivar release from 1966 to 2009, indicating that the current highest yield potential CIMMYT spring wheats have a co-limitation of grain growth by source and sink. This may have been due to an increase in grain sink strength with years of cultivar release with no commensurate increase in post-anthesis source capacity. The relatively low decreases in grain weight with defoliation compared to decreases in light interception by defoliation indicated that sink limitation was still likely predominating in the cultivars with co-limitation. The stem-and-leaf-sheath covering treatment decreased grain weight by nearly 10%, indicating that stem-and-leafsheath photosynthesis plays a key role in grain growth during grain filling. In addition, pre-anthesis reserve contribution to grain weight was increased by ca. 50% in response to lamina defoliation. Our results showed that increasing the post-anthesis source capacity, through increases in stem-and-leaf-sheath photosynthetic rate during grain filling and pre-anthesis reserve contribution to grain weight, is an important objective in enhancing yield potential in wheat through maintaining a source–sink balance.

scholarly journals Inverse modeling of CO<sub>2</sub> sources and sinks using satellite data: a synthetic inter-comparison of measurement techniques and their performance as a function of space and time

2004 ◽  
Vol 4 (2) ◽  
pp. 523-538 ◽  
Author(s):  
S. Houweling ◽  
F.-M. Breon ◽  
I. Aben ◽  
C. Rödenbeck ◽  
M. Gloor ◽  
...  
Keyword(s):  
Near Infrared ◽  
Spatial Scales ◽  
Measurement Techniques ◽  
Data Retrieval ◽  
Sources And Sinks ◽  
Space And Time ◽  
Infra Red ◽  
Temporal And Spatial ◽  
Source And Sink ◽  
Satellite Instruments

Abstract. Currently two polar orbiting satellite instruments measure CO2 concentrations in the Earth's atmosphere, while other missions are planned for the coming years. In the future such instruments might become powerful tools for monitoring changes in the atmospheric CO2 abundance and to improve our quantitative understanding of the leading processes controlling this. At the moment, however, we are still in an exploratory phase where first experiences are collected and promising new space-based measurement concepts are investigated. This study assesses the potential of some of these concepts to improve CO2 source and sink estimates obtained from inverse modelling. For this purpose the performance of existing and planned satellite instruments is quantified by synthetic simulations of their ability to reduce the uncertainty of the current source and sink estimates in comparison with the existing ground-based network of sampling sites. Our high resolution inversion of sources and sinks (at 8°x10°) allows us to investigate the variation of instrument performance in space and time and at various temporal and spatial scales. The results of our synthetic tests clearly indicate that the satellite performance increases with increasing sensitivity of the instrument to CO2 near the Earth's surface, favoring the near infra-red technique. Thermal infrared instruments, on the contrary, reach a better global coverage, because the performance in the near infrared is reduced over the oceans owing to a low surface albedo. Near infra-red sounders can compensate for this by measuring in sun-glint, which will allow accurate measurements over the oceans, at the cost, however, of a lower measurement density. Overall, the sun-glint pointing near infrared instrument is the most promising concept of those tested. We show that the ability of satellite instruments to resolve fluxes at smaller temporal and spatial scales is also related to surface sensitivity. All the satellite instruments performed relatively well over the continents resulting mainly from the larger prior flux uncertainties over land than over the oceans. In addition, the surface networks are rather sparse over land increasing the additional benefit of satellite measurements there. Globally, challenging satellite instrument precisions are needed to compete with the current surface network (about 1ppm for weekly and 8°x10° averaged SCIAMACHY columns). Regionally, however, these requirements relax considerably, increasing to 5ppm for SCIAMACHY over tropical continents. This points not only to an interesting research area using SCIAMACHY data, but also to the fact that satellite requirements should not be quantified by only a single number. The applicability of our synthetic results to real satellite instruments is limited by rather crude representations of instrument and data retrieval related uncertainties. This should receive high priority in future work.

ENERGY EXCHANGE IN A CORN CANOPY

1975 ◽  
Vol 55 (3) ◽  
pp. 691-704
Author(s):  
J. H. McCAUGHEY ◽  
J. A. DAVIES
Keyword(s):  
Sweet Corn ◽  
Exponential Model ◽  
Source Strength ◽  
Net Radiation ◽  
Sources And Sinks ◽  
Transfer Equations ◽  
Solar Noon ◽  
Turbulent Transfer Coefficient ◽  
Source Sink ◽  
The Vertical Distribution

Results from a study of the energy balance within a sweet corn (Zea mays L.) canopy are presented. The downward depletion of hourly net radiation in the canopy is described by a modified exponential model. Temperature, humidity and energy source/sink profiles are discussed at two crop stages. The use of one-dimensional mass transfer equations for sensible and latent heat was satisfactory only under certain conditions of windspeed and wind direction. The vertical distribution of energy sources and sinks changed as the canopy aged. During both sample periods, evaporation was the principal energy user, and its source strength showed two maxima which were most pronounced around solar noon. As the attenuation of net radiation increased after solar noon, the source strength for evaporation returned to a single maximum. The diffusion for all levels in the canopy was turblent. Turblence did not decay exponentially in this canopy. Profiles of the computed turbulent transfer coefficient showed local increases at the base and the center of the canopy probably as a result of increased thermal convection.

scholarly journals Influence of Heat Source/Sink on Free Convection in Annular Porous Region

2021 ◽  
Vol 39 (3) ◽  
pp. 841-850
Author(s):  
Anurag ◽  
Shyam Lal Yadav ◽  
Ashok Kumar Singh
Keyword(s):  
Heat Source ◽  
Darcy Number ◽  
Constant Heat Flux ◽  
Petroleum Engineering ◽  
Temperature Dependent ◽  
Porous Region ◽  
Annular Gap ◽  
Source Sink ◽  
Thermal Technique ◽  
Source And Sink

The significant interpretation of this model is to explore the influence of temperature-dependent heat source/sink on laminar free-convective flow in an annular porous region such as petroleum engineering, thermal technique and groundwater hydrology. For a unified solution of the Brinkman-Darcy model, the regulatory equations solved analytically by applying the variation of parameter technique in terms of Bessel's functions for the heat source and sink. Moreover, we have investigated the Variations of Darcy number, Heat source/sink and viscosity ratio in the presence of isothermal and constant heat flux sequentially. As a result, we received the critical value of the velocity for the radii ratio (R = 2.05 and 2.92) in both the cases of source and sink (S = 1.0 and Si = 0.1) respectively which is exhibited through the graphs. Further, the numerical outcomes present of the skin friction including volume flow with annular gap by the graphs as well as tables.

scholarly journals Genotypic variation in morphological source and sink traits affects the response of rice photosynthesis and growth to elevated atmospheric CO2

2019 ◽  
Author(s):  
Denis Fabre ◽  
Michael Dingkuhn ◽  
Xinyou Yin ◽  
Anne Clément-Vidal ◽  
Sandrine Roques ◽  
...  
Keyword(s):  
Photosynthetic Capacity ◽  
Flag Leaf ◽  
Genotypic Variation ◽  
Growth Cycle ◽  
Plant Production ◽  
Leaf Photosynthesis ◽  
Elevated Atmospheric Co2 ◽  
Rice Genotypes ◽  
Source Sink ◽  
Source And Sink

AbstractThis study aimed to understand the response of photosynthesis and growth to e-CO2conditions (800 vs. 400 μmol mol-1) of rice genotypes differing in source-sink relationships. A proxy trait called local C source-sink ratio was defined as the ratio of flag leaf area over the number of spikelets on the corresponding panicle, and five genotypes differing in this ratio were grown in a controlled greenhouse. Differential CO2resources were applied either during the two weeks following heading (EXP1) or during the whole growth cycle (EXP2). Under e-CO2, low source-sink ratio cultivars (LSS) had greater gains in photosynthesis, and they accumulated less nonstructural carbohydrate in the flag leaf than high source-sink ratio cultivars (HSS). In EXP2, grain yield and biomass gain was also greater in LSS probably caused by their strong sink. Photosynthetic capacity response to e-CO2was negatively correlated across genotypes with local C source-sink ratio, a trait highly conserved across environments. HSS were sink-limited under e-CO2, probably associated with low triose phosphate utilization (TPU) capacity. We suggest that the local C source-sink ratio is a potential target for selecting more CO2-responsive cultivars, pending validation for a broader genotypic spectrum and for field conditions.HighlightRice local carbon source-sink ratio and sink plasticity can drive genotypic responses of leaf photosynthesis and plant production in a CO2elevation context.

scholarly journals Source capacity during flowering affects grain yield of amaranth (Amaranthus sp.)

2013 ◽  
Vol 59 (No. 10) ◽  
pp. 472-477 ◽  
Author(s):  
B. Roitner-Schobesberger ◽  
Kaul H-P
Keyword(s):  
Grain Yield ◽  
Dry Matter ◽  
Field Experiments ◽  
Growth Conditions ◽  
Yield Reduction ◽  
Sources And Sinks ◽  
Yield Level ◽  
Eastern Austria ◽  
Source Sink ◽  
Yield Formation

Amaranth is a promising C4-crop. However, for a wider spread of the crop a better understanding of factors that are influencing yield formation is crucial for optimizing the plant phenotype and enhancing yield. The present study wanted to clarify the effects of assimilate sources and sinks on yield formation by artificially altering source or sink size. Field experiments were conducted in Eastern Austria during three years with three genotypes, applying source-sink manipulation treatments at mid flowering (control, 50% of inflorescence removed, 50% or 100% of leaves removed). At maturity we measured shoot, inflorescence and grain dry matter, thousand kernel mass and number of seeds per plant. An average grain yield level of about 3.5 t/ha dry matter on control plots indicated favorable growth conditions for amaranth in general. The removal of all leaves had a strong detrimental effect on all parameters, but severity of yield reduction due to defoliation differed between genotypes, ranging from &ndash;49% to &ndash;73%. Contrastingly, 50% flower reduction did not have any significant effects. Also with 50% defoliation no significant yield reduction was observed. We conclude that source strength of amaranth during flowering is more yield limiting than its sink capacity.

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