Ainsworth Laboratory

Ainsworth EA, Rogers A, Leakey ADB (2008) Targets for crop biotechnology in a future high-CO2 and high-O3 world . Plant Physiology 147: 13-19.

What are the challenges and opportunities that climate change will present for biotechnological improvement of crop yield and food supply?

Ainsworth EA (2008) Rice production in a changing climate: A meta-analysis of responses to elevated carbon dioxide and elevated ozone concentrations. Global Change Biology 14: 1642-1650.

Rice is arguably the most important food source on the planet and is consumed by over half of the world’s population. While elevated [CO2] stimulated rice yields, elevated temperature negated any enhancement in rice yield at elevated [CO2], which suggests that identifying high temperature tolerant germplasm will be key to realizing yield benefits in the future.

Wittig VE, Ainsworth EA, Long SP (2007) To what extent do current and projected increases in surface ozone affect photosynthesis and stomatal conductance of trees? Plant, Cell & Environment 30: 1150-1162.

The findings suggest that rising ozone, an often overlooked aspect of
global atmospheric change, is progressively depressing the ability of temperate and boreal forests to assimilate carbon and transfer water vapour to the atmosphere, with significant potential effects on terrestrial carbon sinks and regional hydrologies.

Ainsworth EA, Gillespie KM (2007) Estimation of total phenolic content and other oxidation substrates in plant tissues using Folin-Ciocalteu reagent. Nature Protocols, 2: 875-877.

This protocol describes a microplate-adapted colorimetric total phenlics assay that uses Folin-Ciocalteu (F-C) reagent. The F-C assay relies on the transfer of electrons in alkaline medium from phenolic compounds to phosphomolybdic/phosphotungstic acid complexes, which are measured at 765 nm.

Gillespie KM, Ainsworth EA (2007) Measurement of reduced, oxidized and total ascorbate content in plants . Nature Protocols, 2: 871-874.

This protocol describes a microplate-adapted colorimetric ascorbate assay, in which ferric ion is reduced by ascorbate to ferrous ion. The ferrous ion reactions with a-a-bipyridl to form a complex with characteristic absorbance at 525 nm.

Gillespie KM, Chae JM, Ainsworth EA (2007) Rapid measurement of total antioxidant capacity in plants . Nature Protocols, 2: 867-870.

This protocol describes the oxygen radical absorbance capacity (ORAC) assay, which measures antioxidant inhibition of peroxyl radical-induced oxidations and provides a measure of total antioxidant capacity.

Ainsworth EA, Rogers A (2007)The response of photosynthesis and stomatal conductance to rising [CO₂]: Mechanisms and environmental interactions. Plant Cell and Environment 30: 258-270.

This review summarizes current understanding of the mechanisms that underlie the response of photosynthesis and stomatal conductance to elevated carbon dioxide concentration, and examines how downstream processes and environmental constraints modulate these two fundamental responses.

Ainsworth EA, Rogers A, Leakey ADB, Heady LE, Gibon Y, Stitt M, Schurr U (2007) Does elevated atmospheric [CO₂] alter diurnal C uptake and the balance of C and N metabolites in growing and fully expanded soybean leaves? Journal of Experimental Botany 58: 579-591.

Carbon and nitrogen balance was investigated in mature and growing soybean leaves exposed to elevated [CO₂] in a free air CO₂ enrichment facility. Elevated [CO₂] alters the balance of carbon and nitrogen pools in both mature and growing soybean leaves, which could have down-stream impacts on growth and productivity.

Ainsworth EA, Rogers A, Vodkin LO, Walter A, Schurr U (2006) The effects of elevated CO₂ concentration on gene expression. An analysis of growing and mature leaves. Plant Physiology 142: 135-147.

The 327 CO₂-responsive genes suggest that elevated [CO₂] stimulates the respiratory breakdown of carbohydrates, which provides increased energy and biochemical precursors for leaf expansion and growth at elevated [CO₂].

Long SP, Ainsworth EA, Leakey ADB, Nosberger J, Ort DR (2006) Food for thought: Lower than expected crop yield stimulation with rising CO₂ concentrations. Science 312: 1918-1921.

Model projections suggest that although increased temperature and decreased soil moisture will act to reduce global crop yields by 2050, the direct fertilization effect of rising carbon dioxide concentration ([CO₂]) will offset these losses. The CO₂ fertilization factors used in models to project future yields were derived from enclosure studies conducted approximately 20 years ago. Free-air concentration enrichment (FACE) technology has now facilitated large-scale trials of the major grain crops at elevated [CO₂] under fully open-air field conditions. In those trials, elevated [CO₂] enhanced yield by ~50% less than in enclosure studies. This casts serious doubt on projections that rising [CO₂] will fully offset losses due to climate change.

Christ MM, Ainsworth EA, Nelson RL, Schurr U, Walter A (2006) Putative yield loss in field-grown soybean can be avoided at the expense of leaf growth during early reproductive growth stages in favorable environmental conditions.Journal of Experimental Botany, 57: 2267-2275.

Anticipated yield loss under elevated ozone concentration was avoided at the expense of leaf growth, as reserves were diverted from vegetative to reproductive organs.

Leakey ADB, Uribelarrea M, Ainsworth EA, Naidu SL, Rogers A, Ort DR, Long SP (2006) Photosynthesis, productivity and yield of Zea mays are not affected by open-air elevation of CO₂ concentration in the absence of drought. Plant Physiology, 140: 779-790.

The results provide unique field evidence that photosynthesis and production of maize may be unaffected by rising [CO₂] in the absence of drought. This suggests that rising [CO₂] may not provide the full dividend to North American maize production anticipated in projections of future global food supply.

Ainsworth EA, Walter A, Schurr U (2005) Glycine max leaves lack a base-tip gradient in growth rate. Journal of Plant Research, 118: 343-346.

The paradigm of dicotyledonous leaf expansion describes high relative growth rates at the leaf base, dampening towards the leaf tip. In contrast to findings from other species, maximum growth rates occurred at ~2 a.m. and the basipetal growth pattern was absent, suggesting the factors controlling soybean expansion are distinct from other species.

Long SP, Ainsworth EA, Leakey ADB, Morgan PB (2005) Global food insecurity. Treatment of major food crops with elevated carbon dioxide or ozone under large-scale fully open-air conditions suggests recent models may have overestimated future yields. Philosophical Transactions of the Royal Society, 360: 2011-2020.

Free-Air Concentration Enrichment (FACE) technology now allows investigation of the effects of rising [CO₂] and ozone on field crops under fully open-air conditions at an agronomic scale. Experiments with rice, wheat, maize and soybean show smaller increases in yield than anticipated from studies in chambers. Experiments with increased ozone show large yield losses (20%), which are not accounted for in projections of global food security.

Ainsworth EA, Long SP (2005) What have we learned from fifteen years of Free Air Carbon Dioxide Enrichment (FACE)? A Meta-analytic review of the responses of photosynthesis, canopy properties and plant production to rising CO₂. New Phytologist, 165: 351-372.

Free-air CO₂ enrichment (FACE) experiments allow study of the effects of elevated [CO₂] on plants and ecosystems grown under natural conditions without enclosure. Data from 120 primary, peer-reviewed articles describing physiology and production in the 12 large-scale FACE experiments (475–600 ppm) were collected and summarized using meta-analytic techniques.

Ainsworth EA, Rogers A, Nelson RL, Long SP (2004) Testing the "source-sink" hypothesis of down-regulation of photosynthesis in elevated [CO₂] with single gene substitutions in Glycine max. Agricultural and Forest Meteorology, 122: 85-94.

Acclimation of photosynthesis to elevated atmospheric carbon dioxide concentration was tested in lines of soybean (Glycine max) that differed by single genes that altered either the capacity to nodulate or growth habit (determinate or indeterminate growth). Results were consistent with the hypothesis that genetic capacity for the utilization of photosynthate is critical to the ability of plants to sustain increased photosynthesis when grown at elevated [CO₂].

Long SP, Ainsworth EA, Rogers A, Ort DR (2004) Rising atmospheric carbon dioxide: plants FACE the future. Annual Review of Plant Biology, 55: 591-628.

Atmospheric CO₂ concentration ([CO₂]) is now higher than it was at any time in the past 26 million years and is expected to nearly double during this century. Terrestrial plants with the C3 photosynthetic pathway respond in the short term to increased [CO₂] via increased net photosynthesis and decreased transpiration. In the longer term this increase is often offset by down-regulation of photosynthetic capacity. Much of what is currently known about plant responses to elevated [CO₂] comes from enclosure studies, where the responses of plants may be modified by size constraints and the limited life-cycle stages that are examined. Free-Air CO₂ Enrichment (FACE) was developed as a means to grow plants in the field at controlled elevation of CO₂ under fully open-air field conditions. The findings of FACE experiments are quantitatively summarized via meta-analytic statistics and compared to findings from chamber studies. Although trends agree with parallel summaries of enclosure studies, important quantitative differences emerge that have important implications both for predicting the future terrestrial biosphere and understanding how crops may need to be adapted to the changed and changing atmosphere.

Ainsworth EA, Rogers A, Blum H, Nösberger J, Long SP (2003) Variation in acclimation of photosynthesis in Trifolium repens after eight years of exposure to Free Air CO₂ Enrichment (FACE). Journal of Experimental Botany, 54: 2769-2774.

The results show that acclimation of photosynthetic capacity can occur in a nitrogen-fixing species, in the field where there are no artificial restrictions on sink capacity. Despite acclimation of photosynthetic capacity in leaves that developed under elevated [CO₂], the long-term effect of growth at elevated [CO₂] was a 37% increase in
photosynthesis. Thus, contrary to the belief that the response of grassland species to elevated [CO₂] will be
short-lived, stimulation of photosynthesis in T. repens remained after eight years of exposure to elevated [CO₂].

Ainsworth EA, Davey PD, Hymus GJ, Osborne CP, Rogers A, Blum H, Nosberger J, Long SP (2003) Is stimulation of leaf photosynthesis by elevated carbon dioxide concentration maintained in the long term? A test with Lolium perenne grown for ten years at two nitrogen levels under Free Air CO₂ Enrichment (FACE). Plant, Cell & Environment, 26: 705-714.

Ainsworth EA, Davey PD, Hymus GJ, Osborne CP, Rogers A, Blum H, Nosberger J, Long SP (2003) Is stimulation of leaf photosynthesis by elevated carbon dioxide concentration maintained in the long term? A test with Lolium perenne grown for ten years at two nitrogen levels under Free Air CO₂ Enrichment (FACE). Plant, Cell & Environment, 26: 705-714.

Ainsworth EA, Tranel PJ, Drake BG, Long SP (2003) The clonal structure of Quercus geminata revealed by conserved microsatellite loci. Molecular Ecology, 12: 527-532.

The scrub oak communities of the southeastern USA may have existed at their present locations for thousands of years. These oaks form suckers, and excavations of root systems suggest that clones may occupy very large areas. Resolution of the clonal nature of scrub oaks is important both to manage the tracts of this ecosystem that remain, and in conducting long-term ecological studies, where the study area must substantially exceed the area occupied by any single clone.

Morgan PB, Ainsworth EA, Long SP (2003) How does elevated ozone impact soybean? A meta-analysis of photosynthesis, growth and yield. Plant, Cell & Environment, 28: 1317-1328.

Surface ozone concentrations ([O₃]) during the growing season in much of the northern temperate zone reach mean
peak daily concentrations of 60 p.p.b. Concentrations are predicted to continue to rise over much of the globe during
the next 50 years. We review how soybean photosynthesis, growth and yield are impacted by levels of ozone predicted for this century.

Rogers A, Allen DJ, Davey PA, Morgan PB, Ainsworth EA, Bernacchi CJ, Cornic G, Dermody O, Heaton EA, Mahoney J, Zhu X-G, Delucia EH, Ort DR, Long SP (2004) Leaf photosynthesis and carbohydrate dynamics of soybeans grown throughout their life-cycle under Free-Air Carbon dioxide Enrichment. Plant Cell & Environment, 27: 449-458.

Leaf photosynthesis increased in soybeans grown at elevated [CO₂], despite decreases in stomatal conductance. However, increases in photosynthesis were less than predicted, and the indeterminate, N-fixing crop accumulated large amounts of soluble carbohydrates and starch at elevated [CO₂].

Ainsworth EA, Davey PA, Bernacchi CJ, Dermody OC, Heaton EA, Moore DJ, Morgan PB, Naidu SL, Yoo H, Zhu X-G, Curtis PS, Long SP (2002) A meta-analysis of elevated [CO₂] effects on soybean (Glycine max) physiology, growth and yield. Global Change Biology 8: 695-709.

The effects of elevated [CO₂] on 25 variables describing soybean physiology, growth and yield are reviewed using meta-analytic techniques.

Ainsworth EA, Davey PA, Hymus GJ, Drake BG, Long SP (2002) Long-term response of photosynthesis to elevated carbon dioxide in a Florida scrub-oak ecosystem. Ecological Applications 12: 1267-1275.

During the critical phase of canopy closure in a woody community, elevation of [CO₂] caused a species-dependent and time-dependent change in the capacity of the codominants to acquire carbon and energy.