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Plant canopies under drought stress– structures, functions, (genes) and models

Hartmut Stützel and Tsu-Wei Chen. Plant canopies under drought stress– structures, functions, (genes) and models. Plant canopies : structur al and functional properties. L eaf area index I nclination of leaves Leaf angle distribution Leaf curvature O ptical properties

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Plant canopies under drought stress– structures, functions, (genes) and models

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  1. Hartmut Stützeland Tsu-Wei Chen Plant canopies under drought stress– structures, functions, (genes) and models

  2. Plant canopies: structural andfunctionalproperties • Leaf area index • Inclination of leaves • Leafangle distribution • Leafcurvature • Optical properties • Light extinction coefficient • Gap fraction • Internode length • Canopy photosynthesis • CO2transport (stomatal, mesophyllresistance) • Biochemicalconversion (Rubisco, light) • Transpiration • Light intensity, light quality and availability of water Canopiesunder stress

  3. Howarethesefunctionalandstructuralpropertiesinfluencedby stress? Howcanwequantify stress effects on functionandstructure? Canopies under stress

  4. Morphologicaltraitsofwheatasrelatedtowatersupply after datafom Zhang et al. 2011 Canopies under stress

  5. Simulated diurnal time course of net canopyphotosynthesis for a maize crop having leaf area index (L) of 2, 4,or 8 and average leaf inclination from the horizontal of (a) 40°or (b) 80°. Simulation conducted for Day 180 of the year at Johnston,IA (41°40′ N lat) Hammer et al. 2009 Canopiesunder stress

  6. Simulatedeffectsofincreasinganddecreasingleaf angle by 30 % on light extinctioncoefficientand Light interceptionoftomatocanopies 130% 70% Canopy light interception: 78% Light extinctioncoefficient: 0.60±0.02 Canopy light interception: 49% Light extinctioncoefficient 0.27±0.01 Chen et al. 2014, J. exp. Bot., accepted Canopiesunder stress

  7. Response of net photosynthetic CO2 assimilation (PN) to intercellular CO2 concentration (ci) of barley plants grown at ambient (A) and elevated (B) [CO2] and subjected to well-watered conditions (circles) or 9 (squares), 13 (triangles) and 16 d (diamonds) of water stress. Robredo et al. 2010 Canopies under stress

  8. Generalizedresponseofnetphotosynthesis (AN) andseveralparametersrelatedtophotosyntheticcapacitytowater stress whenusingdailymaximumleafstomatalconductance(gs) content as the reference for stress intensity Flexas et al. 2012 Canopiesunder stress

  9. Modelling canopyprocesses Big leafmodels: treat the canopy as an extended leaf (or a small set of large leaves), map the properties of a whole canopy onto a single leaf (or a fewleaves, Amthor, 1994) Sunlit-shademodels: divide the (big leaf) canopy and leaf nitrogen between sunlit and shaded leaves (de Pury and Farquhar 1997) Multi-layer models: canopy is divided into layers, each with different light level, predicted by Beer’s law, and differentiation into sunlit and shade leaves (including a sunfleck penetration), a coupled scheme of leaf photosynthesisandstomatalconductance (Clark et al., 2011) → noprecisepredictionofthespatial and temporal hetero-geneities of light inside a canopy Canopiesunder stress

  10. Diurnal canopy CO2 uptake rate (Ac) of a rice canopy calculated with average photosynthetic photon flux density (PPFD) at different layers of a canopy (average light) compared with Ac calculated using the detailed PPFD of each individual facet in the canopy (detailed light). Song et al. 2013 Canopiesunder stress

  11. Spatially explicit modelsofcanopies: Functional-structural plant models (FSPM) Environment Structure Functions Simulate plant growth and development based on individual organs Explicitly allow for feedbacks between plant structure and plant function Interactions between organs Canopies are constructed as assemblies of plants Static Dynamic Canopiesunder stress

  12. Dynamic cucumberarchitecture model Environment Structure Functions Canopiesunder stress

  13. The virtual 2 m cucumber canopy with 18 plants, constructed using digitized data in GroIMP, in top view (A) and side view (B). Canopiesunder stress Chen et al. 2014; doi:10.1093/aob/mcu100

  14. An exampleofdynamicfunctional-structural plant model (L-Peach, Allen, PrusinkiewiczandDeJong, 2005)

  15. Functional-structuralmodels: researchquestions • Spatial integration of processes • Effects of physiological limitations on canopy performance • Effectsof light direction (e.g. direct/diffuse) on growth • Disentanglingphysiologicalfrommorphologicaleffects • Influence of canopy architecture modifications: row width, plant density etc. • Assessment of plant traits: breeding, pruning …. Canopiesunder stress

  16. Simulated leaf photosynthesis rate under 100 % direct light and 100 % diffuse light in a cucumber canopy Canopiesunder stress Chen et al. 2014; doi:10.1093/aob/mcu100

  17. Analysis oflimitationstoproductivity: • Physiological limitations • Photosynthesis • CO2diffusion • Biochemicalapparatus • Light • Structurallimitations • Leafarea • Leafareadistribution • Leafexposition: leaf angle, azimuth angle Canopies under stress

  18. Calculationofphotosyntheticlimitations due tobiochemical, lightanddiffusionalfactors Reference photosynthesis rate Biochemicallimitation Currentphotosynthesis rate Light limitation Diffusionallimitation CurrentCO2 conc. Canopiesunder stress

  19. Changes of stomatal, (B) mesophyll, (C) diffusional (stomatal + mesophyll), (D) biochemical, (E) light and (F) total (diffusional + biochemical + light) limitations with leaf rank (counted from bottom to top) and light conditions above the canopy (79 % direct light and 21 % diffuse light) Canopiesunderstress Chen et al. 2014; doi:10.1093/aob/mcu100

  20. Canopies under stress Chen et al. 2014; doi:10.1093/aob/mcu100

  21. Simulated relationships between water potential in the root zone and photosynthetic limitations of a cucumber leaf on day 15 after leaf appearance. The environmental conditions were: ambient CO2 concentration = 380 ppm, water vapour deficit = 0.87 kPa, leaf absorbed light intensity = 800 µmol m-2s-1, and leaf temperature = 25°C. Canopiesunder stress

  22. Simulatedeffectsofdrought stress (soilwater potential - 0.4 MPa) on photo-synthesis rates at different positions in a cucumbercanopy Canopiesunder stress

  23. Simulatedeffectsofdrought stress (soilwater potential - 0.4 MPa) on lightuseefficienciesat different positions in a cucumbercanopy Canopiesunder stress

  24. Influenceofdrought stress (water potential Ψs = -0.4MPa in therootzone) on canopyphotosynthesisand light useefficiency in different positionsofthecanopy Canopiesunder stress

  25. What happens under salinity? Osmotic stress Ionic stress (ion accumulation) red. Toxic Light interception red. Stom. conduct. red. Biochemical capacity Non-architecturaleffects Ion accumulation Photosynthesis Transpiration Light use efficiency Architecturaleffects Organ size Canopiesunder stress

  26. y = 100 -0.34x R2 = 0.91 y = 100 -0.49x R2 = 0.99 Effectofsalinity on shoot dry mass on day 77 after thefirstleafappearanceunder 22/18°C (low temperature) and 32/28°C (high temperature) day/night temperature conditions Canopiesunder stress

  27. Relative light use efficiency at three salinity levels under low (LT, 22/18°C) and high (HT, 32/28°C) day/night temperature conditions Canopiesunder stress

  28. Total andarchitecturaleffectsofsalinity on shoot dry mass on day 77 after thefirstleafappearanceunder 22/18°C (low temperature) and 32/28°C (high temperature) day/night temperature conditions Canopiesunder stress

  29. Conclusions A canopyismorethan a bigleaf Canopystructurehas strong impact on productivityandresourceuse → optimization Systematicanalysisofarchitecturaleffects on productivityandresourceuseis just at thebeginning FSPM aremodels Canopiesunder stress

  30. Thankyou! Canopiesunder stress

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