Dr. Asaph Cousins


Professor, School of Biological Sciences. Ph.D. 2001, Arizona State University.
Asaph Cousins.


The ability to monitor and predict how plants both influence and are influenced by future climatic conditions is critical for the health of our planet and for future food production. My research couples molecular biology techniques with plant physiology and mathematical modeling of photosynthesis to understand the mechanistic processes dictating plant-environment interactions.

This research uses a variety of experimental techniques, including field experiments, leaf and whole plant gas exchange, recombinant DNA techniques, biochemistry, and metabolite analysis to elucidate how the interactions of plant light utilization, carbon and nutrient assimilation, and isotope discrimination are influenced by changing environmental conditions. The two main areas my research is focusing on are the following:

1) Plant energy metabolism Understanding the flow of energy between metabolic pathways and organelles is important for determining how plants will respond to environmental stress and future climatic conditions. This research uses gas exchange, mass spectrometry and metabolite analysis to understand the key steps in photosynthesis, photorespiration and nitrogen metabolism that coordinate the energy flow between these competing processes.

2) Carbon and oxygen isotope exchange in plants Isotope analysis of atmospheric CO2 is an important tool for monitoring ecosystem changes in plant metabolism in response to climate change. However, to interpret the atmospheric CO2 isotopic signature requires an understanding of the fractionation steps associated with specific processes during leaf gas exchange. This research uses molecular tools coupled with stable isotope analysis and mathematical modeling of photosynthesis and isotope exchange to understand how leaf metabolism and anatomy influence the exchange of carbon and water between plants and their environment.

Selected Publications

Feldman M., Ellsworth P.Z., Fahlgren N., Gehan M.A., Cousins A.B., Baxter I.R. (2018) Components of water use efficiency have unique genetic signatures in the model C4grass Setaria. Plant Physiol. doi: 10.1104/pp.18.00146.

Alonso-Cantabrana H., Cousins A.B., Danila F.R., Ryan T., Sharwood R.E., von Caemmerer S., Furbank R.T. (2018) Diffusion of CO2 across the mesophyll-bundle sheath cell interface in a C4 plant with genetically reduced PEP carboxylase activity. Plant Physiol. doi: 10.1104/pp.18.00618.

Kolbe A.R., Brutnell T.P., Cousins A.B., Studer A.J. (2018) Carbonic Anhydrase Mutants in Zea mays Have Altered Stomatal Responses to Environmental Signals. Plant Physiol. 177: 980-989

Ellsworth P.V., #Ellsworth P.Z., Cousins A.B. (2018) Cell wall properties in Oryza sativa influence mesophyll CO2conductance. New Phytiologist 219, 66-76

Ubierna N., Gandin A., Cousins A.B. (2018) The response of mesophyll conductance to short-term variation in CO2in three C4species. Journal of Exp Botany 69, 1159-1170

Kolbe A.R., Cousins A.B. (2018) Mesophyll conductance in Zea mays responds transiently to CO2 availability: implications for transpiration efficiency in C4 crops. NewPhytologistDOI:10.1111/nph.14942

Kolbe A.R., Studer A.J., Cousins A.B. (2018) Biochemical and transcriptomic analysis of maize diversity to elucidate drivers of leaf carbon isotope composition Functional Plant Biology https://doi.org/10.1071/FP17265

Ellsworth P.Z., Ellsworth P.V., Cousins A.B. (2017) Measurements of Leaf Oxygen and Carbon Isotopic Signatures to estimate Transpiration Efficiency in the C4 Grasses Setaria viridis and Setaria italica. Journal of Exp BotanyJournal of Exp Botany 68, 3513-3528

Ubierna N., Gandin A., Boyd R.A., Cousins A.B. (2017) Temperature response of mesophyll conductance in three C4species calculated with two methods: 18O discrimination and in-vitroVpmax New PhytologistDoi: 214, 66-80

Walker B., Cousins A.B. (2013) Temperature dependent increases in photorespiratory CO2 release in Arabidopsis thaliana: Implications to leaf CO2 gas exchange. Journal of Experimental Biology Accepted

Busch F., Sage, T.L., Cousins A.B., Sage, R.F. (2013) C3 plants enhance rates of photosynthesis by reassimilating photorespired and respired CO2. Plant, Cell and Environment 36:200-212

Ubierna N., Sun W., Cousins A.B. (2013) The efficiency of C4 photosynthesis under low light conditions in Zea mays, iscanthus x giganteus and Flaveria bidentis. Plant, Cell and Environment 36:365-381

Gandin A., Duffes C., Day D.A., Cousins A.B. (2012) The absence of alternative oxidase AOX1A results in altered response of photosynthetic carbon assimilation to increasing CO2 in Arabidopsis thaliana. Plant, Cell and Physiology 59:1627-1637

King J.L., Edwards G.E., Cousins A.B. (2012) The efficiency of the CO2-concentrating mechanism during single-cell C4 photosynthesis. Plant Cell and Environment 35, 513-523

Sun, W, Ubierna, N, Ma, JY, and Cousins A.B. (2012). The influence of light quality on C4 photosynthesis under steady-state conditions in Zea mays and Miscanthus × giganteus: changes in rates of photosynthesis but not the efficiency of the CO2 concentrating mechanism. Plant, Cell & Environment 35, 982-993

Ubierna N., Sun W., Cousins A.B. (2011) The efficiency of C4 photosynthesis under low light conditions: assumptions and calculations with CO2 isotope discrimination. Journal of Experimental Botany 62, 3119-3134

Cousins A.B., Walker B. Pracharoenwattana I., Smith S.M., Badger M.R. (2011) A non-lethal disruption of photorespiration alters the stoichiometry of Rubisco oxygenation and photorespiratory release of CO2 Photosynthesis Research 108, 91-100

Bloom A.J., Randall R., Rachmilevitch S., Cousins A.B., Carlisle E. (2011) CO2 enrichment inhibits shoot nitrate assimilation in C3 but not C4 plants and slows growth under nitrate in C3 plants. Ecology 93, 355-367

Kodama N., Cousins A.B., Tu K.P., Barbour M.M. (2011) Spatial variation in photosynthetic carbon and oxygen isotope discrimination along leaves of the monocot Triticale (Triticum × Secale) relates to mesophyll conductance and the Péclet effect. Plant Cell and Environment 34, 1548-1562

Bloom A.J., Asensio J.S.R., Burger M & Cousins A.B. (2010) Carbon Dioxide Enrichment Inhibits Nitrate Assimilation in Wheat and Arabidopsis Science In press

Edwards E.J., et al. (2010) The Origins of C4 Grasslands: Integrating Evolutionary and Ecosystem Science In press

Cousins A.B., Ghannoum, O., Badger M.R., von Caemmerer S. (2010) Measuring Rubisco kinetics with a membrane inlet mass spectrometer. Plant Cell and Environment 33, 444-452

Cousins A.B., Baroli I., Badger M.R., Ivakov A., Lea P.J., Leegood R.C., von Caemmerer S. (2007) The role of PEPc during photosynthetic isotope exchange and stomatal conductance. Plant Physiology In press

Griffiths H., Cousins A.B., Badger M.R., and von Caemmerer S (2007) Discrimination in the dark: resolving the interplay between metabolic and physical constraints to PEPC activity during the CAM cycle. Plant Physiology 143, 1055-1067

Cousins A.B., Badger M.R., von Caemmerer S. (2006) A transgenic approach to understanding the influence of carbonic anhydrase on C18OO discrimination during C4 photosynthesis. Plant Physiology 142, 662-672

Cousins A.B., Badger M., von Caemmerer S. (2006) Carbonic anhydrase and its influence on carbon isotope discrimination during C4 photosynthesis: Insights from antisense RNA in Flaveria bidentis. Plant Physiology 141, 232-242

Cousins A.B. and Bloom A.J. (2004) Oxygen consumption during leaf nitrate assimilation in a C3 and C4 plant: the role of mitochondrial respiration. Plant Cell and Environment. 27, 1537-1545.

Rachmilevitch S., Cousins A.B. and Bloom A.J. (2004) Nitrate assimilation in plant shoots depends on photorespiration. Proceedings of the National Academy of Sciences.101, 11506-11510 Cousins A.B. (2004). Man bests machine, this time. The Scientist. 18: 58.

Cousins A.B. and Bloom A.J. (2003) Influence of elevated CO2 and nitrogen nutrition on photosynthesis and nitrate photoassimilation in maize (Zea mays L.). Plant Cell and Environment 26, 1525-1530.

Cousins A.B., Adam N.R., Wall G.W., Kimball B.A., Pinter Jr. P.J., Ottman M.J., Webber A.N. (2003) Development of C4 photosynthesis in Sorghum leaves grown under free-air CO2 enrichment (FACE) Journal of Experimental Botany 54, 1969-1975.

Cousins A.B., Adam N.R., Wall G.W., Kimball B.A., Ottman M.J., Webber A.N. (2002) Photosystem II energy use, non-photochemical quenching and the xanthophyll cycle in Sorghum bicolor grown under drought and Free-Air CO2 Enrichment (FACE) conditions. Plant Cell and Environment 25, 1551-1559

Cousins A.B., Adam N. R., Wall G.W., Kimball B.A., Pinter Jr. P.J., Leavitt S.W., LaMorte R.L., Matthias A.D., Ottman M.J., Thompson T.L., Webber A.N. (2001) Reduced photorespiration and increased energy-use efficiency in young CO2-enriched sorghum leaves. New Phytologist 150, 275-284.