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Anthony P Ogrady - One of the best experts on this subject based on the ideXlab platform.

  • whole plant versus leaf level regulation of photosynthetic responses after partial defoliation in eucalyptus globulus saplings
    Journal of Experimental Botany, 2013
    Co-Authors: Alieta Eyles, E A Pinkard, Anthony P Ogrady, Noel W Davies, Ross Corkrey, Keith Churchill
    Abstract:

    Increases in photosynthetic capacity (A1500) after defoliation have been attributed to changes in leaf-level biochemistry, water, and/or nutrient status. The hypothesis that transient photosynthetic responses to partial defoliation are regulated by whole-plant (e.g. source–sink Relationships or changes in hydraulic conductance) rather than leaf-level mechanisms is tested here. Temporal variation in leaf-level gas exchange, chemistry, whole-plant soil-to-leaf hydraulic conductance (KP), and aboveground biomass partitioning were determined to evaluate mechanisms responsible for increases in A1500 of Eucalyptus globulus L. potted saplings. A1500 increased in response to debudding (B), partial defoliation (D), and combined B&D treatments by up to 36% at 5 weeks after treatment. Changes in leaf-level factors partly explained increases in A1500 of B and B&D treatments but not for D treatment. By week 5, saplings in B, B&D, and D treatments had similar leaf-specific KP to control trees by maintaining lower midday water potentials and higher transpiration rate per leaf area. Whole-plant source:sink ratios correlated strongly with A1500. Further, unlike KP, temporal changes in source:sink ratios tracked well with those observed for A1500. The results indicate that increases in A1500 after partial defoliation treatments were largely driven by an increased demand for assimilate by developing sinks rather than improvements in whole-plant water relations and changes in leaf-level factors. Three carbohydrates, galactional, stachyose, and, to a lesser extent, raffinose, correlated strongly with photosynthetic capacity, indicating that these sugars may function as signalling molecules in the regulation of longer term defoliation-induced gas exchange responses.

  • are gas exchange responses to resource limitation and defoliation linked to source sink Relationships
    Plant Cell and Environment, 2011
    Co-Authors: E A Pinkard, A Eyles, Anthony P Ogrady
    Abstract:

    Productivity of trees can be affected by limitations in resources such as water and nutrients, and herbivory. However, there is little understanding of their interactive effects on carbon uptake and growth.We hypothesized that: (1) in the absence of defoliation, photosynthetic rate and leaf respiration would be governed by limiting resource(s) and their impact on sink limitation; (2) photosynthetic responses to defoliation would be a consequence of changing source:sink Relationships and increased availability of limiting resources; and (3) photosynthesis and leaf respiration would be adjusted in response to limiting resources and defoliation so that growth could be maintained. We tested these hypotheses by examining how leaf photosynthetic processes, respiration, carbohydrate concentrations and growth rates of Eucalyptus globulus were influenced by high or low water and nitrogen (N) availability, and/or defoliation. Photosynthesis of saplings grown with low water was primarily sink limited, whereas photosynthetic responses of saplings grown with low N were suggestive of source limitation. Defoliation resulted in source limitation. Net photosynthetic responses to defoliation were linked to the degree of resource availability, with the largest responses measured in treatments where saplings were ultimately source rather than sink limited. There was good evidence of acclimation to stress, enabling higher rates of C uptake than might otherwise have occurred.

Michael Dingkuhn - One of the best experts on this subject based on the ideXlab platform.

  • genotypic variation in source and sink traits affects the response of photosynthesis and growth to elevated atmospheric co2
    Plant Cell and Environment, 2020
    Co-Authors: Denis Fabre, Michael Dingkuhn, Xinyou Yin, Anne Clementvidal, Sandrine Roques, Armelle Soutiras, Delphine Luquet
    Abstract:

    This study aimed to understand the response of photosynthesis and growth to e‐CO2 conditions (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 to the number of spikelets on the corresponding panicle, and five genotypes differing in this ratio were grown in a controlled greenhouse. Differential CO2 resources were applied either during the 2 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‐CO2 was 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.

  • genotypic variation in morphological source and sink traits affects the response of rice photosynthesis and growth to elevated atmospheric co2
    bioRxiv, 2019
    Co-Authors: Denis Fabre, Michael Dingkuhn, Xinyou Yin, Anne Clementvidal, Sandrine Roques, Armelle Soutiras, Delphine Luquet
    Abstract:

    Abstract This study aimed to understand the response of photosynthesis and growth to e-CO2 conditions (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 CO2 resources 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-CO2 was 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. Highlight Rice local carbon Source-Sink ratio and sink plasticity can drive genotypic responses of leaf photosynthesis and plant production in a CO2 elevation context.

  • role of triose phosphate utilization in photosynthetic response of rice to variable carbon dioxide levels and plant source sink relations
    bioRxiv, 2019
    Co-Authors: Denis Fabre, Michael Dingkuhn, Xinyou Yin, Anne Clementvidal, Sandrine Roques, Armelle Soutiras, Lauriane Rouan, Delphine Luquet
    Abstract:

    Abstract This study aimed to understand the physiological bases of rice photosynthesis response to C Source-Sink imbalances, with focus on dynamics of the photosynthetic parameter TPU (Triose Phosphate Utilization). A dedicated experiment was replicated twice on IR64 indica rice cultivar in controlled environments. Plants were grown under the current ambient CO2 concentration until heading, thereafter, two CO2 treatments (400 and 800 μmol mol−1) were compared in the presence and absence of a panicle pruning treatment modifying the C sink. At two weeks after heading, photosynthetic parameters derived from CO2 response curves, and nonstructural carbohydrate content of flag leaf and internodes were measured 3-4 times of day. Spikelet number per panicle and flag leaf area on the main culm were recorded. Net C assimilation and TPU decreased progressively after midday in panicle-pruned plants, especially under 800 μmol mol−1. This TPU reduction was explained by sucrose accumulation in the flag leaf resulting from the sink limitation. It is suggested that TPU is involved in rice photosynthesis regulation under elevated CO2 conditions, and that sink limitation effects should be considered in crop models. Highlight This study provide new insights in the effect of C Source-Sink Relationships on rice photosynthesis. TPU should be considered in photosynthesis studies under severe Source-Sink imbalance at elevated CO2.

  • simulation of inflorescence dynamics in oil palm and estimation of environment sensitive phenological phases a model based analysis
    Functional Plant Biology, 2013
    Co-Authors: Jeanclaude Combres, Lauriane Rouan, Isabelle Mialetserra, Jeanpierre Caliman, Benoit Pallas, Serge Braconnier, Jeanchristophe Soulie, Michael Dingkuhn
    Abstract:

    For oil palm, yield variation is in large part due to variation in the number of harvested bunches. Each successively-produced phytomer carries a female (productive), male or aborted inflorescence. Since phytomer development takes 3–4 years and nearly two phytomers are produced per month, many inflorescences develop in parallel but have different phenological stages. Environment-dependent developmental rate, sex and abortion probability determine bunch productivity, which, in turn, affects other phytomers via source–sink Relationships. Water deficit, solar radiation, temperature and day length are considered key external factors driving variation. Their impact is difficult to predict because of system complexity. To address this question we built a simple model (ECOPALM) to simulate the variation in number of harvested bunches. In this model, trophic competition among organs, expressed through a plant-scale index (Ic), drives sex determination and inflorescence abortion during specific sensitive phases at phytomer level. As a supplemental hypothesis, we propose that flowering is affected by photoperiod at phytomer level during a sensitive phase, thus, contributing to seasonal production peaks. The model was used to determine by parameter optimisation the influence of Ic and day length on inflorescence development and the stages at which inflorescences are sensitive to these signals. Parameters were estimated against observation of number of harvested bunches in Ivory Coast using a genetic algorithm. The model was then validated with field observations in Benin and Indonesia. The sensitive phases determined by parameter optimisation agreed with independent experimental evidence, and variation of Ic explained both sex and abortion patterns. Sex determination seemed to coincide with floret meristem individualisation and occurred 29–32 months before bunch harvest. The main abortion stage occurred 10 months before harvest – at the beginning of rapid growth of the inflorescence. Simulation results suggest involvement of photoperiod in the determination of bunch growth dynamics. This study demonstrates that simple modelling approaches can help extracting ecophysiological information from simple field observations on complex systems.

  • phenology growth and physiological adjustments of oil palm elaeis guineensis to sink limitation induced by fruit pruning
    Annals of Botany, 2009
    Co-Authors: Sandrine Legros, Denis Fabre, Anne Clementvidal, Isabelle Mialetserra, Jeanpierre Caliman, Fahri Arief Siregar, Michael Dingkuhn
    Abstract:

    † Background and Aims Despite its simple architecture and small phenotypic plasticity, oil palm has complex phenology and source –sink interactions. Phytomers appear in regular succession but their development takes years, involving long lag periods between environmental influences and their effects on sinks. Plant adjustments to resulting source –sink imbalances are poorly understood. This study investigated oil palm adjustments to imbalances caused by severe fruit pruning. † Methods An experiment with two treatments (control and complete fruit pruning) during 22 months in 2006– 2008) and six replications per treatment was conducted in Indonesia. Phenology, growth of above-ground vegetative and reproductive organs, leaf morphology, inflorescence sex differentiation, dynamics of non-structural carbohydrate reserves and light-saturated net photosynthesis (Amax) were monitored. † Key Results Artificial sink limitation by complete fruit pruning accelerated development rate, resulting in higher phytomer, leaf and inflorescence numbers. Leaf size and morphology remained unchanged. Complete fruit pruning also suppressed the abortion of male inflorescences, estimated to be triggered at about 16 months before bunch maturity. The number of female inflorescences increased after an estimated lag of 24 –26 months, corresponding to time from sex differentiation to bunch maturity. The most important adjustment process was increased assimilate storage in the stem, attaining nearly 50 % of dry weight in the stem top, mainly as starch, whereas glucose, which in controls was the most abundant non-structural carbohydrate stored in oil palm, decreased. † Conclusions The development rate of oil palm is in part controlled by source– sink Relationships. Although increased rate of development and proportion of female inflorescences constituted observed adjustments to sink limitation, the low plasticity of plant architecture (constant leaf size, absence of branching) limited compensatory growth. Non-structural carbohydrate storage was thus the main adjustment process.

Jean Dauzat - One of the best experts on this subject based on the ideXlab platform.

  • Carbon allocation in fruit trees: from theory to modelling
    Trees, 2008
    Co-Authors: Michel Génard, Jean Dauzat, Nicolás Franck, Françoise Lescourret, Nicolas Moitrier, Philippe Vaast, Gilles Vercambre
    Abstract:

    Carbon allocation within a plant depends on complex rules linking source organs (mainly shoots) and sink organs (mainly roots and fruits). The complexity of these rules comes from both regulations and interactions between various plant processes involving carbon. This paper presents these regulations and interactions, and analyses how agricultural management can influence them. Ecophysiological models of carbon production and allocation are good tools for such analyses. The fundamental bases of these models are first presented, focusing on their underlying processes and concepts. Different approaches are used for modelling carbon economy. They are classified as empirical, teleonomic, driven by source–sink Relationships, or based on transport and chemical/biochemical conversion concepts. These four approaches are presented with a particular emphasis on the regulations and interactions between organs and between processes. The role of plant architecture in carbon partitioning is also discussed and the interest of coupling plant architecture models with carbon allocation models is highlighted. As an illustration of carbon allocation models, a model developed for peach trees, describing carbon transfer within the plant, and based on source–sink and Münch transport theory is presented and used for analyzing the link between roots, shoots and reproductive compartments. On this basis, the consequences of fruit load or plant pruning on fruit and vegetative growth can be evaluated.

  • soluble sugars mediate sink feedback down regulation of leaf photosynthesis in field grown coffea arabica
    Tree Physiology, 2006
    Co-Authors: Nicolás Franck, Michel Génard, Philippe Vaast, Jean Dauzat
    Abstract:

    Source-Sink Relationships of field-grown plants of Coffea arabica L. cultivar 'Caturra' were manipulated to analyze the contribution of soluble sugars to sink feedback down-regulation of maximal leaf net CO2 assimilation rate (Amax). Total soluble sugar concentration (SSCm) and Amax were measured in the morning and afternoon on mature leaves of girdled branches bearing either high or low fruit loads. Leaf Amax was negatively correlated to SSCm, increased with fruit load and decreased during the day, indicating that limiting sink demand for carbohydrates caused SSCa, to accumulate in the leaf tissue which results in down-regulation of Amax. To further analyze Source-Sink feedback on Am,x, we compared Amax of mature, non-sink-limited coffee leaves fed with water or sucrose for 5, 10 or 30 min with that of non-fed control leaves. Sucrose-feeding reduced Amax compared with the control and water-feeding treatments, indicating that down-regulation of Amax is related to phloem sucrose concentration in coffee source leaves, independent of SSC m concentration in other leaf tissues. Although sucrose appeared to be more closely related to the mechanism underlying sink feedback down-regulation of Amax in coffee leaves than SSCm, Amax was closely related to SSCm by a non-linear equation that may be useful for integrating sink limitations in coffee leaf photosynthetic models. (Resume d'auteur)

  • Soluble sugars mediate sink feedback down-regulation of leaf photosynthesis in field-grown Coffea arabica
    Tree Physiology, 2006
    Co-Authors: Nicolás Franck, Michel Génard, Philippe Vaast, Jean Dauzat
    Abstract:

    Source-Sink Relationships of field-grown plants of Coffea arabica L. cultivar' Caturra' were manipulated to analyze the contribution of soluble sugars to sink feedback downregulation of maximal leaf net CO2 assimilation rate (A(max)). Total soluble sugar concentration (SSCm) and A(max) were measured in the morning and afternoon on mature leaves of girdled branches bearing either high or low fruit loads. Leaf A(max) was negatively correlated to SSCm increased with fruit load and decreased during the day, indicating that limiting sink demand for carbohydrates caused SSCm to accumulate in the leaf tissue which results in down-regulation of A(max). To further analyze Source-Sink feedback on A(max) we compared A(max) of mature, non-sink-limited coffee leaves fed with water or sucrose for 5, 10 or 30 min with that of non-fed control leaves. Sucrose-feeding reduced A(max) compared with the control and water-feeding treatments, indicating that down-regulation of A(max) is related to phloem sucrose concentration in coffee source leaves, independent of SSCm concentration in other leaf tissues. Although sucrose appeared to be more closely related to the mechanism underlying sink feedback down-regulation of A(max) in coffee leaves than SSCm, A(max) was closely related to SSCm by a non-linear equation that may be useful for integrating sink limitations in coffee leaf photosynthetic models.

F H Andrade - One of the best experts on this subject based on the ideXlab platform.

  • maize grain yield components and source sink relationship as affected by the delay in sowing date
    Field Crops Research, 2016
    Co-Authors: Lucas E Bonelli, J P Monzon, Anibal Cerrudo, Roberto H Rizzalli, F H Andrade
    Abstract:

    Abstract Delaying maize ( Zea mays L.) sowing date can diminish grain yields through reductions in the number, size and activity of growing grains (sink strength) and/or reductions in the assimilate supply (source capacity) to grains during the grain filling period. Whether the source capacity or the sink strength is the limiting factor for grain yield in late sown maize still remains unclear. Understanding Source-Sink Relationships is relevant to optimize crop management practices, to identify critical processes for crop modelling and to develop breeding strategies. The objective of this work was to assess the effect of delays in maize sowing date on grain yield components and on the Source-Sink relationship during the grain filling period. Three well irrigated and fertilized maize field experiments were conducted at Balcarce, Argentina (37° 45′ S, 58° 18′ W; 130 m a.s.l.) during 2009–10; 2010–11 and 2011–12 cropping seasons. Sowing dates ranged from October to January covering a broad range of the seasonal photo-thermal variation. Grain yield was affected by sowing date and varied from 1680 g m −2 (early sowings) to 203 g m −2 (late sowings). Grain number per unit area was reduced proportionally less than weight per grain as sowing date was delayed. Variations in grain yield were related to the harvest index, and were closely associated with dry matter accumulation during the post-silking period. The variation of source capacity was higher than that of sink strength during the grain filling period and the source/sink ratio decreased from early to late sowing dates. Results indicate that crop growth during the grain filling period was limited by the sink strength in early sowing dates and by the photosynthetic source capacity in the late ones.

Denis Fabre - One of the best experts on this subject based on the ideXlab platform.

  • genotypic variation in source and sink traits affects the response of photosynthesis and growth to elevated atmospheric co2
    Plant Cell and Environment, 2020
    Co-Authors: Denis Fabre, Michael Dingkuhn, Xinyou Yin, Anne Clementvidal, Sandrine Roques, Armelle Soutiras, Delphine Luquet
    Abstract:

    This study aimed to understand the response of photosynthesis and growth to e‐CO2 conditions (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 to the number of spikelets on the corresponding panicle, and five genotypes differing in this ratio were grown in a controlled greenhouse. Differential CO2 resources were applied either during the 2 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‐CO2 was 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.

  • genotypic variation in morphological source and sink traits affects the response of rice photosynthesis and growth to elevated atmospheric co2
    bioRxiv, 2019
    Co-Authors: Denis Fabre, Michael Dingkuhn, Xinyou Yin, Anne Clementvidal, Sandrine Roques, Armelle Soutiras, Delphine Luquet
    Abstract:

    Abstract This study aimed to understand the response of photosynthesis and growth to e-CO2 conditions (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 CO2 resources 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-CO2 was 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. Highlight Rice local carbon Source-Sink ratio and sink plasticity can drive genotypic responses of leaf photosynthesis and plant production in a CO2 elevation context.

  • role of triose phosphate utilization in photosynthetic response of rice to variable carbon dioxide levels and plant source sink relations
    bioRxiv, 2019
    Co-Authors: Denis Fabre, Michael Dingkuhn, Xinyou Yin, Anne Clementvidal, Sandrine Roques, Armelle Soutiras, Lauriane Rouan, Delphine Luquet
    Abstract:

    Abstract This study aimed to understand the physiological bases of rice photosynthesis response to C Source-Sink imbalances, with focus on dynamics of the photosynthetic parameter TPU (Triose Phosphate Utilization). A dedicated experiment was replicated twice on IR64 indica rice cultivar in controlled environments. Plants were grown under the current ambient CO2 concentration until heading, thereafter, two CO2 treatments (400 and 800 μmol mol−1) were compared in the presence and absence of a panicle pruning treatment modifying the C sink. At two weeks after heading, photosynthetic parameters derived from CO2 response curves, and nonstructural carbohydrate content of flag leaf and internodes were measured 3-4 times of day. Spikelet number per panicle and flag leaf area on the main culm were recorded. Net C assimilation and TPU decreased progressively after midday in panicle-pruned plants, especially under 800 μmol mol−1. This TPU reduction was explained by sucrose accumulation in the flag leaf resulting from the sink limitation. It is suggested that TPU is involved in rice photosynthesis regulation under elevated CO2 conditions, and that sink limitation effects should be considered in crop models. Highlight This study provide new insights in the effect of C Source-Sink Relationships on rice photosynthesis. TPU should be considered in photosynthesis studies under severe Source-Sink imbalance at elevated CO2.

  • phenology growth and physiological adjustments of oil palm elaeis guineensis to sink limitation induced by fruit pruning
    Annals of Botany, 2009
    Co-Authors: Sandrine Legros, Denis Fabre, Anne Clementvidal, Isabelle Mialetserra, Jeanpierre Caliman, Fahri Arief Siregar, Michael Dingkuhn
    Abstract:

    † Background and Aims Despite its simple architecture and small phenotypic plasticity, oil palm has complex phenology and source –sink interactions. Phytomers appear in regular succession but their development takes years, involving long lag periods between environmental influences and their effects on sinks. Plant adjustments to resulting source –sink imbalances are poorly understood. This study investigated oil palm adjustments to imbalances caused by severe fruit pruning. † Methods An experiment with two treatments (control and complete fruit pruning) during 22 months in 2006– 2008) and six replications per treatment was conducted in Indonesia. Phenology, growth of above-ground vegetative and reproductive organs, leaf morphology, inflorescence sex differentiation, dynamics of non-structural carbohydrate reserves and light-saturated net photosynthesis (Amax) were monitored. † Key Results Artificial sink limitation by complete fruit pruning accelerated development rate, resulting in higher phytomer, leaf and inflorescence numbers. Leaf size and morphology remained unchanged. Complete fruit pruning also suppressed the abortion of male inflorescences, estimated to be triggered at about 16 months before bunch maturity. The number of female inflorescences increased after an estimated lag of 24 –26 months, corresponding to time from sex differentiation to bunch maturity. The most important adjustment process was increased assimilate storage in the stem, attaining nearly 50 % of dry weight in the stem top, mainly as starch, whereas glucose, which in controls was the most abundant non-structural carbohydrate stored in oil palm, decreased. † Conclusions The development rate of oil palm is in part controlled by source– sink Relationships. Although increased rate of development and proportion of female inflorescences constituted observed adjustments to sink limitation, the low plasticity of plant architecture (constant leaf size, absence of branching) limited compensatory growth. Non-structural carbohydrate storage was thus the main adjustment process.