Location: Plant Physiology and Genetics Research2012 Annual Report
1a. Objectives (from AD-416):
Objective 1. Assess the relative utility of experimental approaches such as FACE, SPAR, OTC and T-FACE for estimating impacts of climate change factors on plant responses. Objective 2. Strengthen physiological and genetic assumptions of ecophysiological models used for climate change research. Sub-objective 2.A: Compare and refine ecophysiological models that differ in the level of complexity used to represent key processes. Sub-objective 2.B: Refine and apply approaches for gene-based modeling of ecotypic adaptations to factors relevant to climate change research. Objective 3. Predict likely impacts of climate change and potential for adaptation of cropping systems.
1b. Approach (from AD-416):
To achieve the first objective, we will capitalize on the extensive wheat datasets from research at Maricopa over the past 20 years as well as recent advances in statistical analysis of simulation outputs. The second objective builds on progress in plant physiology and genomics that provide avenues for improving how processes are modeled, especially in relation to cultivar differences. In the third objective, the advances in modeling and understanding will be applied to irrigated production systems of the Southwest, both to assess potential impacts of climate change and to identify options for adaptation, including potentially complex interactions of crop calendars, cultivar types and irrigation and fertilizer management. By addressing strategic methodological constraints, the research will provide invaluable information for stakeholders in regional, national and international venues, helping to ensure that agriculture can adapt efficiently and effectively to climate change.
3. Progress Report:
The project seeks to improve prediction of impacts of increased CO2 and climate uncertainty on crop production. Our focus is on application of field data through simulation models that encapsulate knowledge of ecophysiology, agroclimatology and allied fields. These models are recognized as among the best options for examining complex interactions among environment and crop management. Progress in model improvement under Objectives 1 (“Assess the relative utility of experimental approaches…”) has slowed due to unexpected findings by ARS Researchers at Beltsville, MD, that short-term (e.g., 30 second) fluctuations in CO2 strongly inhibit crop growth. The previous assumption was that differences among methods for measuring responses to CO2 likely involved artifacts such as shading. Thus, such differences likely also include responses to fluctuating CO2, and previous estimated CO2 effects on growth and yield may be too low. CO2 fluctuations occur with all experimental CO2 enrichment methods, but few experimenters have documented CO2 fluctuations or included side-by-side comparisons among enrichment methods. The proposed mechanism relates to asymmetric stomatal responses. These can be modeled, but this requires a better, more quantitative understanding. Our project is assisting in compiling historic datasets on CO2 fluctuations and in designing future experiments. Emphasis has also shifted in Sub-objective 2.B (“Refine and apply approaches for gene-based modeling of ecotypic adaptations to factors relevant to climate change research”). Knowing genotypes for key traits is insufficient to predict useful plant traits (“phenotypes”). This genotype-to-phenotype (G2P) problem has led researchers to scale up field measurements from perhaps two to ten cultivars to measurements on hundreds to thousands of breeding lines. Such “high throughout phenotyping” (HTP) dictates use of vehicles carrying multiple electronic sensors as well as novel approaches to data analysis through simulation modeling. Our project members are contributing expertise in ecophysiology, modeling and data management in field research that targets cotton, wheat and biofuel crops but seeks flexible systems applicable to other crops. We propose to modify our research activities to accommodate HTP for heat and drought stress. Improving the physiological hypotheses represented in the models requires detailed information on crop management, soils and daily weather. The project has continued locating, converting and reformatting data for use with crop models, emphasizing wheat and sorghum. A major effort has gone toward revising data standards which are being used not only in our own work but in the global Agricultural Model Intercomparison and Improvement Project (AgMIP). We continue to test the standards for the Decision Support System for Agrotechnology Transfer (DSSAT) models, and through AgMIP, the data standards are being tested with other models.
1. Finalized version 2 of the ICASA data standards. Numerous research applications require integrating data from multiple experiments and locations. However, such integration is often difficult because even when as digital files, datasets lack key information and are not organized according to avaliable standard for formatting. The standards developed by the International Consortium for Agricultural Systems Analysis provide a robust framework for describing crop management, environmental conditions and field measurements. ARS researchers at Maricopa, AZ, in collaboration with colleagues at the University of Florida finalized the version 2 standards, which are the first revision in over 10 years. This revision will allow researchers to exchange data much more efficiently and ensuring that experiments are fully characterized for analysis.
2. Review of approaches for field-based, high-throughput phenotyping (HTP). Improving our ability to predict potential adaptation to climate change, especially through breeding of new cultivars, requires new approaches for evaluating large numbers of traits (“phenotypes”) in field environments. ARS Researchers at Maricopa, AZ, conducted a major review of suitable sensors and associated methods for deploying sensors and analyzing data with emphasis on traits related to heat and drought tolerance. The review indicates major opportunities using simulation models to interpret data from tractor-mounted sensors. This information provides the foundation for developing major efforts to develop HTP capabilities and apply them in crop genetics and breeding, ultimately leading to higher and more stable yielding cultivars.
3. Elevated atmospheric CO2 and drought effects on leaf gas exchange properties of barley. Atmospheric CO2 concentration is rising, predicted to cause global warming and alter precipitation patterns. Uncertainty exists about how barley production will be affected by elevated atmospheric CO2 under ample and reduced water supply. ARS researchers from Maricopa, AZ, USA, and Potsdam-Institute for Climate Impact Research, Potsdam, Germany fumigated open-field barley plots with CO2 to 180 ppm above ambient levels of 370 ppm. Elevated CO2 facilitated drought avoidance by reducing water loss through leaves (reduced stomatal conductance by 34%) which conserved water and enabled leaves to transpire for a longer period into a drought, resulting in a 28% reduction in drought-induced, midafternoon depression in photosynthesis rate. The season-long average dry weight increased by 14%, under elevated CO2, whereas deficit irrigation reduced it by 7%. Hence, effects of elevated-CO2 on gas exchange properties enhanced growth of barley.
4. Elevated levels of ozone cause decreased water use of soybean. Tropospheric ozone is increasing in many agricultural regions resulting in decreased stomatal conductance and overall growth and yield of sensitive crop species. To assess likely future effects on future water use, ARS researchers from Urbana, IL, and Maricopa, AZ, fumigated open-field soybean plots with ozone to achieve concentrations from 22 and 37% above background. The elevated ozone decreased water use by as much as 15% in high ozone years and decreased soil water removal while increasing canopy temperature up to 0.7°C. The lower water use could enable soybeans to survive longer periods of drought, whereas the increased temperature could exacerbate tissue damage from this pollutant gas.
5. Guidebook written to facilitate mitigation of greenhouse gas emissions. Earth’s temperature is warming globally, and the increase in temperature is being attributed to rising concentrations of “greenhouse” gases associated with the burning of fossil fuels. Agriculture contributes only 13% of the total emissions of such gases to the atmosphere, but any reductions in emissions of these gases would help solve a global problem. Therefore, sponsored by the United Nations Environment Programme, an ARS researcher from Maricopa, AZ, collaborating with scientists from India, Denmark, and China helped write a guidebook, “Technologies for Climate Change Mitigation in The Agricultural Sector” that lists and reviews methods for reducing the emissions of CO2, CH4, and N2O that are associated with agriculture. The book lists a whole suite of technologies including sixteen methods related to crop management and seven related to livestock and manure management, as well as organic farming and bioenergy.
6. Excess water loss from infrared warming of field plots is quantified. In order to study the likely effects of global warming on future ecosystems, including agricultural fields, a method for applying a warming treatment to open-field plant canopies [i.e., a temperature free-air controlled enhancement (T-FACE) system] is needed which will warm vegetation as expected by the future climate. One method which shows promise is infrared heating. However, warming by infrared heating also increases the rate of transpiration from the crop beyond that expected with a true simulation of conditions expected with global warming. Working with researchers from Belgium and Italy, an ARS researcher from Maricopa, AZ, helped perform detailed calculations of the percentage increases in transpiration for several cases. The calculation method will enable more precise determinations of the amounts of supplemental irrigation water needed in such experiments to compensate for the extra transpiration.
Ottman, M.J., Kimball, B.A., White, J.W., Wall, G.W. 2011, Wheat growth response to increased temperature from varied planting dates and supplemental infrared heating. Agronomy Journal, 104(1):7-16.