Assessing photosynthetic downregulation in sunflower stands with an optically-based model

Using a simple light-use efficiency model based on optical measurements, we explored spatial patterns of photosynthetic activity in fertilized and unfertilized sunflower stands. The model had two components: (1) absorbed photosynthetically active radiation (APAR), and (2) radiation-use efficiency. APAR was the product of photosynthetic photon flux density (PPFD) and leaf absorptance, which was derived from leaf reflectance. Radiation-use efficiency was either assumed to be constant or allowed to vary linearly with the photochemical reflectance index (PRI), a measure of xanthophyll cycle pigment activity. When efficiency was assumed to be constant, the model overestimated photosynthetic rates in upper canopy layers exposed to direct PPFD, particularly in the unfertilized canopy due to the greater photosynthetic downregulation associated with higher levels of photoprotective (de-epoxidized) xanthophyll cycle pigments in these conditions. When efficiency was allowed to vary according to the PRI, modeled photosynthetic rates closely matched measured rates for all canopy layers in both treatments. These results illustrate the importance of considering reduced radiation-use efficiency due to photosynthetic downregulation when modeling photosynthesis from reflectance, and illustrate the potential for detecting radiation-use efficiency through leaf optical properties. At least under the conditions of this study, these results also suggest that xanthophyll cycle pigment activity and net carbon uptake are coordinately regulated, allowing assays of Photosystem II activity to reveal changing rates of net assimilation. Because the optical methods in this study are adaptable to multiple spatial scales (leaf to landscape), this approach may provide a scalable model for estimating photosynthetic rates independently from flux measurements.

[1]  T. Sharkey,et al.  End product feedback effects on photosynthetic electron transport , 2004, Photosynthesis Research.

[2]  J. William Munger,et al.  Measurements of carbon sequestration by long‐term eddy covariance: methods and a critical evaluation of accuracy , 1996 .

[3]  S. Wofsy,et al.  Scaling gross ecosystem production at Harvard Forest with remote sensing: a comparison of estimates from a constrained quantum‐use efficiency model and eddy correlation , 1995 .

[4]  C. Field,et al.  Relationships Between NDVI, Canopy Structure, and Photosynthesis in Three Californian Vegetation Types , 1995 .

[5]  C. Field,et al.  Scaling Physiological Processes: Leaf to Globe , 1995 .

[6]  J. Aber,et al.  A generalized, lumped-parameter model of photosynthesis, evapotranspiration and net primary production in temperate and boreal forest ecosystems , 1992, Oecologia.

[7]  Richard H. Waring,et al.  Environmental Limits on Net Primary Production and Light‐Use Efficiency Across the Oregon Transect , 1994 .

[8]  J. Randerson,et al.  Terrestrial ecosystem production: A process model based on global satellite and surface data , 1993 .

[9]  J. Peñuelas,et al.  Relationship between photosynthetic radiation-use efficiency of barley canopies and the photochemical reflectance index (PRI) , 1996 .

[10]  G. J. Collatz,et al.  Comparison of Radiative and Physiological Effects of Doubled Atmospheric CO2 on Climate , 1996, Science.

[11]  Klaus Winter,et al.  Photochemical efficiency of photosystem II, photon yield of O2 evolution, photosynthetic capacity, and carotenoid composition during the midday depression of net CO2 uptake in Arbutus unedo growing in Portugal , 1989, Planta.

[12]  S. Linder.  Seasonal Variation of Pigments in Needles A Study of Scots Pine and Norway Spruce Seedlings Grown under Different Nursery Conditions , 2004 .

[13]  M. Losada,et al.  The Assimilatory Nitrate-Reducing System and its Regulation , 1981 .

[14]  John A. Gamon,et al.  Assessing leaf pigment content and activity with a reflectometer , 1999 .

[15]  J. Berry,et al.  A biochemical model of photosynthetic CO2 assimilation in leaves of C3 species , 1980, Planta.

[16]  C. Neubauer,et al.  Mehler-peroxidase reaction mediates zeaxanthin formation and zeaxanthin-related fluorescence quenching in intact chloroplasts. , 1992, Plant physiology.

[17]  D. Ort,et al.  Consideration of photosynthetic efficiency at low light as a major determinant of crop photosynthetic performance , 1988 .

[18]  Ranga B. Myneni,et al.  Potential gross primary productivity of terrestrial vegetation from 1982 - 1990 , 1995 .

[19]  S. Goward,et al.  Global Primary Production: A Remote Sensing Approach , 1995 .

[20]  C. Field,et al.  A narrow-waveband spectral index that tracks diurnal changes in photosynthetic efficiency , 1992 .

[21]  J. Gamon,et al.  The photochemical reflectance index: an optical indicator of photosynthetic radiation use efficiency across species, functional types, and nutrient levels , 1997, Oecologia.

[22]  R. Leuning,et al.  Microclimate above grass adversely affects spring growth of seedling snow gum (Eucalyptus pauciflora) , 1997 .

[23]  C. Field,et al.  Ecosystem gas exchange in a California grassland : seasonal patterns and implications for scaling , 1995 .

[24]  O. Björkman,et al.  Leaf Xanthophyll content and composition in sun and shade determined by HPLC , 1990, Photosynthesis Research.

[25]  Franco Miglietta,et al.  Effects of lifelong (CO2) enrichment on carboxylation and light utilization of Quercus pubescens Willd. examined with gas exchange, biochemistry and optical techniques , 2000 .

[26]  D. Greer,et al.  Photoinhibition of Photosynthesis Causes a Reduction in Vegetative Growth Rates of Dwarf Bean (Phaseolus vulgaris) Plants , 1995 .

[27]  J. Peñuelas,et al.  Assessment of photosynthetic radiation‐use efficiency with spectral reflectance , 1995 .

[28]  C. Field,et al.  Responses of photosynthesis and carbohydrate-partitioning to limitations in nitrogen and water availability in field-grown sunflower , 1991 .

[29]  B. Demmig‐Adams,et al.  Regulation of Photosynthetic Light Energy Capture, Conversion, and Dissipation in Leaves of Higher Plants , 1994 .

[30]  W. W. Adams,et al.  Enhanced Employment of the Xanthophyll Cycle and Thermal Energy Dissipation in Spinach Exposed to High Light and N Stress , 1997, Plant physiology.

[31]  C. R. Ireland,et al.  Measurements of the quantum yield of carbon assimilation and chlorophyll fluorescence for assessment of photosynthetic performance of crops in the field , 1989 .

[32]  R. L. Warner,et al.  Oxygen and carbon dioxide fluxes from barley shoots depend on nitrate assimilation. , 1989, Plant physiology.

[33]  B. Genty,et al.  The relationship between CO2 assimilation and electron transport in leaves , 1990, Photosynthesis Research.

[34]  Steven W. Running,et al.  Strategies for measuring and modelling carbon dioxide and water vapour fluxes over terrestrial ecosystems , 1996 .

[35]  S. Long,et al.  The occurrence of photoinhibition in an over-wintering crop of oil-seed rape (Brassica napus L.) and its correlation with changes in crop growth. , 1991, Planta.

[36]  A. Gitelson,et al.  Spectral reflectance changes associated with autumn senescence of Aesculus hippocastanum L. and Acer platanoides L. leaves. Spectral features and relation to chlorophyll estimation , 1994 .

[37]  Dennis D. Baldocchi,et al.  Seasonal variation of energy and water vapor exchange rates above and below a boreal jack pine forest canopy , 1997 .

[38]  C. Field,et al.  Contrasting leaf and ‘ecosystem’ CO2 and H2O exchange in Avena fatua monoculture: Growth at ambient and elevated CO2 , 1995, Photosynthesis Research.

[39]  Edwin T. Engman,et al.  Status of remote sensing algorithms for estimation of land surface state parameters , 1995 .

[40]  D. Roberts,et al.  MODELING CO 2 FLUX OF BOREAL FORESTS USING NARROW-BAND INDICES FROM AVIRIS IMAGERY , 2000 .

[41]  John M. Norman,et al.  A comparison of six methods for measuring soil‐surface carbon dioxide fluxes , 1997 .

[42]  Josep Peñuelas,et al.  Evaluating Wheat Nitrogen Status with Canopy Reflectance Indices and Discriminant Analysis , 1995 .

[43]  Christopher B. Field,et al.  Production efficiency in sunflower: The role of water and nitrogen stress , 1997 .

[44]  Joseph A. Berry,et al.  Photosynthesis: principles and field techniques. , 2000 .

[45]  J. Randerson,et al.  Primary production of the biosphere: integrating terrestrial and oceanic components , 1998, Science.

[46]  S. Wofsy,et al.  Physiological responses of a black spruce forest to weather , 1997 .

[47]  John Moncrieff,et al.  The propagation of errors in long‐term measurements of land‐atmosphere fluxes of carbon and water , 1996 .

[48]  W. Oechel,et al.  Plant Response to Stress , 1987, NATO ASI Series.

[49]  T. A. Black,et al.  Remote sensing of photosynthetic-light-use efficiency of boreal forest , 2000 .

[50]  Paul G. Jarvis,et al.  Scaling processes and problems , 1995 .

[51]  Ramakrishna R. Nemani,et al.  Relating seasonal patterns of the AVHRR vegetation index to simulated photosynthesis and transpiration of forests in different climates , 1988 .

[52]  M. Sjöström,et al.  Estimation of the effect of photoinhibition on the carbon gain in leaves of a willow canopy , 1990, Planta.

[53]  Shashi B. Verma,et al.  Micrometeorological methods for measuring surface fluxes of mass and energy , 1990 .

[54]  G. Russell,et al.  Plant Canopies: Their Growth, Form and Function: Absorption of radiation by canopies and stand growth , 1989 .

[55]  T. Lamaze,et al.  Adaptation of the Photosynthetic Apparatus in Maize Leaves as a Result of Nitrogen Limitation : Relationships between Electron Transport and Carbon Assimilation. , 1990, Plant physiology.

[56]  C. Tucker,et al.  North American vegetation patterns observed with the NOAA-7 advanced very high resolution radiometer , 1985, Vegetatio.

[57]  J. Monteith.  Climate and the efficiency of crop production in Britain , 1977 .

[58]  Christopher B. Field,et al.  Remote sensing of the xanthophyll cycle and chlorophyll fluorescence in sunflower leaves and canopies , 1990, Oecologia.

[59]  D. Bartlett,et al.  Use of vegetation indices to estimate indices to estimate intercepted solar radiation and net carbon dioxide exchange of a grass canopy , 1989 .