of Plant Sciences
University of California at Davis
Davis, CA 95616
(530) 752-1743 office
(530) 752-7482 laboratory
(530) 752-9659 fax
MOOC (massive open online course) at www.climatechangecourse.org
B.A.; Physics; Yale University; June, 1971
Ph.D.; Biology; Stanford University; January, 1979
Landesanstalt fur Immissionschutz, Essen, Germany
July, 1971 - August, 1972
Institute of Arctic Biology, U. of Alaska, Fairbanks
September, 1978 - September, 1980
Dept. of Botany, U. of California, Davis
October, 1980 - November, 1981
Assistant, Associate, Full Professor, and Chair
Dept. of Plant Sciences, U. of California, Davis
December, 1981 - Present
Honors and Distinctions
Graduated cum laude, 1971
William Bates Traveling Fellow, 1971
NIH Training Grant Fellow, 1972 - 1976
Ph.D. with distinction, 1979
Plant Biology Distinguished Lecturer, UCLA, 1994
NSF Panel Member: Physiological Ecology & Population Biology 1983
NSF Panel Member: Biological Instrumentation 1989-1990
NSF Panel Member: Ecological & Evolutionary Physiology 1992-1996
NASA Science Working Group on the Space Station 1992-1996
DOE Panel Member: Photosynthesis in Nature 1993
Chair, Rockefeller Advisory Seminar, International Agriculture 1995
USDA Panel Member: Forest/Range/Crop/Aquatic Ecosystems 1996
NASA Panel Member: Space Biology 1998-2000
Department Chair: Department of Vegetable Crops 1997-2002
President, Davis Chapter: Agricultural Honor Society 2002-2004
UCís Faculty Rep.: Federal Demonstration Partnership 2002-2007
Ceres Corporation: Consultant 2005-2007
Plant, Cell & Environment: Editorial Review Board 2006-present
Wilbur-Ellis Corporation: Expert Witness 2006
J. Sci. Food & Agric.: Associate Editor 2008-2010
Science Reviewer: Climate Literaracy & Energy Awareness Network 2010
Head Editor: Climate Change Collection, Encyclopedia of Earth 2011
Nitrogen availability, low temperatures, and elevated carbon dioxide are
interrelated environmental factors that strongly influence crop production.
Nitrogen is the inorganic nutrient that plants require in greatest quantity
and that most frequently limits productivity in agricultural systems. To
insure high yields, farmers in the U.S. apply over 11 million metric tons
of nitrogen fertilizer annually; manufacture and distribution of this fertilizer
account for over one-third of the total energy expended in agriculture.
Low soil temperatures
not only inhibit all root metabolic functions, but can cause permanent
damage. Many crops are chilling sensitive so that brief
exposures to temperatures lower than 10°C result in significant losses.
In California, low temperatures define the growing season for most vegetables.
Although elevated CO2 dramatically stimulates short-term carbon fixation
in C3 plants, its effect on longer-term productivity is highly variable.
Some vegetables such as tomato and cucumber suffer declining yields under
elevated CO2, while others show only slight gains. With atmospheric concentrations
of CO2 increasing by over 0.5% year and CO2 fertilization of greenhouse vegetables
becoming more commonplace, elevated CO2 is no longer just a laboratory phenomenon.
Our research focuses
on the interrelations among these factors and addresses the following issues:
(a) chilling tolerance in tomato, and (b) effects of elevated
CO2 on plant carbon-nitrogen relations.
Chilling Tolerance in Tomato
Cultivated tomato is a classic example of a chilling-sensitive species for which temperatures below 6°C, but above freezing, inflict significant injury. In contrast, wild relatives native to the Andes thrive at chilling temperatures. A process that differs between these two groups is root-shoot signaling: upon exposure to cold soils that impede water movement, roots of chilling-tolerant species generate signals that flow through xylem sap and prompt stomatal closure, whereas roots of chilling-sensitive species seem to lack such signals, and shoots continue to transpire and suffer wilting.
In a backcross population between chilling-sensitive and -tolerant tomato species, a quantitative trait locus (QTL) on chromosome 9 (stm9) had the largest effect on shoot turgor maintenance under root chilling, explaining over 30% of phenotypic variance. Near-isogenic lines (NILs) were used to map stm9 within a 2.7 cM region (genome of the chilling-tolerant species has not yet been sequenced, and the number of genes in this region is not known). Analysis of xylem sap from paired NILs for stm9 and their response to artificial xylem sap implicated certain small molecules as a signal. The proposed research will characterize plant responses to these small molecules and will begin to determine the role of this signaling mechanism for belowground stress.
Elevated Carbon Dioxide
Plants, with few exceptions, acquire most of their N as the inorganic ions ammonium and nitrate. I have developed a wide range of methods to assess ammonium and nitrate absorption from the rhizosphere, their translocation through a plant, and their assimilation into organic N compounds. These methods all confirm that atmospheric CO2 enrichment severely inhibits nitrate assimilation in the shoots of most plant species.
One mechanism responsible for this inhibition involves photorespiration. Photorespiration, contrary to popular opinion, is not a wasteful process. It enhances sequentially a) NADP+ reduction in the chloroplast, b) malate export from the chloroplast, c) NADH availability in the cytoplasm, and d) reduction of nitrate; to nitrite, the first step of nitrate assimilation. Rising atmospheric levels of CO2 decrease photorespiration and thereby limit shoot nitrate assimilation.
The relationship among CO2 enrichment, photorespiration, and nitrate assimilation explains a wide range of phenomena.
- Over 95% of higher plant species still rely solely on C3 fixation even after 20 million years of atmospheric CO2 concentrations below 400 ppm and multiple introductions of the C4 pathway. C3 fixation is more efficient than previously thought because C3 plants allocate the energy released from oxidizing RuBP to nitrate assimilation.
- Plant responses to CO2 enrichment are highly variable and dependent on their N status. Plants vary greatly in their relative dependence on ammonium and nitrate as N sources. C3 plants that are highly dependent on ammonium tend to respond positively to CO2 enrichment, whereas those dependent on nitrate tend to respond negatively because CO2 inhibition of shoot nitrate assimilation leads to organic N deficiencies.
- Declines in forest health and food quality that are associated with climate change derive in part from CO2 inhibition of nitrate assimilation that diminishes plant organic N levels. This exacerbates damage from insects and other pests as they consume more plant material to meet their nutritional needs.
Roy K, Bloom
D (1971) tRNA separations using benzolated DEAE-cellulose. In: Cantoni
G, Davies D (eds) Procedures in Nucleic Acid Research. Harper
and Row, New York, pp 524-541
Kuelske S, Bloom AJ (1973) Testing an area source model through application
to an isolated area source and simultaneous concentration measurements. VDI
Chapin FS, III, Bloom AJ (1976) Phosphate absorption: adaptation of tundra
graminoids to a low temperature, low phosphorus environment. Oikos 26:111-121
Zeiger E, Bloom AJ, Hepler PK (1978) Ion transport in stomatal guard cells:
a chemiosmotic hypothesis. What's New in Plant Physiology 9:29-32
Bloom AJ (1979) Salt requirement for Crassulacean Acid Metabolism in the
annual succulent, Mesembryanthemum crystallinum. Plant Physiol 63:749-753
Bloom AJ (1979) Diurnal ion fluctuations in the mesophyll tissue of the
Crassulacean Acid Metabolism plant, Mesembryanthemum crystallinum. Plant
Bloom AJ, Troughton JH (1979) High productivity and photosynthetic flexibility
in a CAM plant. Oecologia (Berl) 38:35-43
Gulmon SL, Bloom AJ (1979) C3 photosynthesis and high temperature acclimation
of CAM in Opuntia basilaris Englem. and Bigel. Oecologia (Berl) 38:217-222
Bloom AJ, Mooney
HA, Björkman O, Berry J (1980) Materials and methods
for carbon dioxide and water exchange analysis. Plant Cell Environ 3:371-376
Bloom AJ, Chapin FS, III (1981) Differences in steady-state net ammonium
and nitrate influx by cold and warm adapted barley varieties. Plant Physiol
Bloom AJ, Epstein E (1984) Varietal differences in salt-induced respiration
in barley. Plant Sci Letts 35:1-3
Schulze E-D, Bloom AJ (1984) Relationship between mineral nitrogen influx
and transpiration in radish and tomato. Plant Physiol 76:827-828
Bloom AJ (1985) Wild and cultivated barleys show similar affinities for
mineral nitrogen. Oecologia (Berl) 65:555-557
Bloom AJ, Chapin
FS, Mooney HA (1985) Resource limitation in plants—an
economic analogy. Ann Rev Ecol Syst 16:363-92
Bloom AJ, Finazzo J (1985) The influence of ammonium and chloride on potassium
and nitrate absorption by barley roots depends on time of exposure and cultivar.
Plant Physiol 81:67-69
Bloom AJ (1986) Plant economics. Trends Ecol Evol 1:98-100
Bloom AJ (1986) Use nitrogen more effectively. American Vegetable Grower,
Western Perspective 34:32-34
Chapin FS, Bloom AJ, Field CB, Waring RH (1987) Plant responses to multiple
environmental factors. BioSci 37:49-57
Bloom AJ, Smart D (1987) Species variation in the absorption of mineral
nitrogen. Proc Hydroponics Soc Am 8:104-113
Bloom AJ (1988) Ammonium and nitrate as nitrogen sources for plant growth.
ISI Atlas of Science 1:55-59
Bloom AJ, Caldwell RM (1988) Root excision decreases nutrient absorption
and gas fluxes. Plant Physiol 87:794-796.
Smart D, Bloom AJ (1988) The kinetics of ammonium and nitrate absorption
in cultivated and wild species of Lycopersicon. Oecologia (Berl.) 76:336-340.
Bloom AJ (1989a) Continuous and steady-state nutrient absorption by intact
plants. In: Torrey JG, Winship LJ (eds) Applications of Continuous and Steady-State
Methods to Root Biology. Martinus Nijhoff Publishers, Dordrecht, 147-163.
Bloom AJ, Dvorák J (1989) Salt-tolerant Triticum × Lophopyrum
derivatives limit the accumulation of sodium and chloride ions. Plant Cell
Bloom AJ (1989b) Principles of instrumentation for physiological ecology.
In: Pearcy RW, Ehleringer JR, Mooney HA, Rundel P (eds) Physiological Plant
Ecology: Field Methods and Instrumentation. Chapman and Hall, New York, 1-13.
Bloom AJ, Caldwell RM, Finazzo J, Warner RL, Weissbart J (1989) Oxygen and
carbon dioxide fluxes from barley shoots depend on nitrate assimilation.
Plant Physiol 91:352-356.
Henriksen GH, Bloom AJ, Spanswick RM (1990) Measurement of net fluxes of
ammonium and nitrate at the surface of barley roots using ion-selective microelectrodes.
Plant Physiol 93:271-280.
Bloom AJ, Sukrapanna SS (1990) Effects of exposure to ammonium and transplant
shock upon the induction of nitrate absorption. Plant Physiol 94:85-90.
Jackson LE, Bloom AJ (1990) Root distribution in relation to nitrogen availability
in field-grown tomatoes. Plant Soil 128:115-126.
Smart DR, Bloom
AJ (1991) Influence of root NH4+ and NO3¯ content on
the temperature response of net NH4+ and NO3¯ uptake in chilling sensitive
and chilling resistant Lycopersicon taxa. J Exp Bot 42:331-338.
Koch G, Bloom AJ, Chapin FS (1991) Ammonium and nitrate as nitrogen sources
in two Eriophorum species. Oecologia Berlin) 88:570-573.
Amthor JS, Koch GW, Bloom AJ (1992) CO2 inhibits respiration in leaves of
Rumex crispus L. Plant Physiol 98:757-760.
Bloom AJ, Sukrapanna SS, Warner RL (1992) Root respiration associated with
ammonium and nitrate absorption and assimilation by barley. Plant Physiol
Bloom AJ, Jackson LE, Smart DR (1993) Root growth as a function of ammonium
and nitrate in the root zone. Plant Cell Environ 16:199-206.
Smart DR, Bloom
AJ (1993) The relationship between kinetics of NH4+ and NO3¯ absorption
and growth in the cultivated tomato (Lycopersicon esculentum Mill. cv.
Plant Cell Environ 16:259-267.
Kosola KR, Bloom AJ (1994) Methylammonium as a transport analog for ammonium
in tomato (Lycopersicon esculentum). Plant Physiol 104:435-442.
Bloom AJ (1994) Crop acquisition of ammonium and nitrate. In: Boote KJ,
Bennett JM, Sinclair TR, Paulsen GM (eds) Physiology and Determination of
Crop Yield. ASA, CSA, SSSA, Madison, WI. 303-310.
Jackson LE, Bloom AJ (1994) Assessment of methylammonium as an analog for
ammonium in plant uptake from soil. Plant Soil 164:195-202.
Kosola KR, Bloom AJ (1996) Chlorate as a transport analog for nitrate absorption
by roots of tomato (Lycopersicon esculentum). Plant Physiol 110:1293-1299.
Evans RD, Bloom AJ, Sukrapanna SS, Ehleringer JR (1996) Nitrogen isotope
composition of tomato (Lycopersicon esculentum Mill. cv T-5) grown under
ammonium or nitrate nutrition. Plant Cell Environ 11:1317-1323
Bloom AJ (1996) Nitrogen dynamics in plant growth systems. Life Support
Biosphere Sci 3:35-41.
Nicoulaud BAL, Bloom AJ (1996) Plant growth, urea absorption and assimilation
under urea applied foliarly as the sole nitrogen source for tomato. J Am
Soc Hort Sci 121:1117-1121.
Bloom AJ (1997) Nitrogen as a limiting factor: crop acquisition of ammonium
and nitrate. In: Jackson LE (ed) Agricultural Ecology. Academic Press, San
Diego, pp. 145-172.
Bloom AJ (1997) Interactions between inorganic nitrogen nutrition and root
development. J Plant Nutri Soil Sci 160:253-259.
Bloom AJ, Randall LB, Meyerhoff PA, St. Clair DA (1998) The chilling sensitivity
of root ammonium influx in a cultivated and wild tomato. Plant Cell Environ
Colmer TD, Bloom
AJ (1998) A comparison of net NH4+ and NO3– fluxes
along roots of rice and maize. Plant Cell Environ 21:240-246.
Nicoulaud BAL, Bloom AJ (1998) Nickel supplements improve growth when foliar
urea is the sole nitrogen source for tomato. J Am Soc Hort Sci 123:556-559.
Smart DR, Bloom
AJ (1998) Investigations of ion absorption during NH4+ exposure: I. Relationship
between H+ efflux and NO3– absorption. J Exp Bot 49:
Bloom AJ (1998) Chapter 5. Mineral Nutrition. In: Taiz L, Zeiger E (eds)
Plant Physiology, 2nd Edition. Sinauer Assoc., Sunderland, MA, pp. 103-124.
Bloom AJ (1998) Chapter 12. Assimilation of Mineral Nutrition. In: Taiz
L, Zeiger E (eds) Plant Physiology, 2nd Edition. Sinauer Assoc., Sunderland,
MA, pp. 323-345.
Smart DR, Ritchie K, Bloom AJ, Bugbee BB (1998) Nitrogen balances for wheat
canopies (Triticum aestivum cv Veery 10) grown under elevated CO2. Plant
Cell Environ 21:753-764.
Nicoulaud BAL, Bloom AJ (1998) Ammonium does not induce ammonium absorption
in nitrogen sufficient tomatoes. J Amer Soc Hort Sci 123:787-790.
Taylor AR, Bloom AJ (1998) Ammonium, nitrate, and proton fluxes along the
maize root. Plant Cell Environ 21:1255-1263.
Bloom AJ, Taylor
AR (2000) Active ion transport in plants. In Kung S –D,
Yang S –F, eds, Discoveries in Plant Science — Volume 3, Singapore,
World Scientific, pp. 411-421.
Truco MJ, Randall
LB, Bloom AJ, St.Clair DA (2000) Detection of QTL associated with shoot
and root ammonium uptake under chilling temperatures in
an interspecific backcross population from Lycopersicon esculentum × L.
hirsutum. Theor. Appl. Genet.101:1082-1092.
Bloom, A. J., and Holbrook, N. M. (2001) United Kingdoms. Plant Physiology 126:952-955.
Smart DR, Bloom AJ (2001) Wheat leaves emit nitrous oxide during nitrate assimilation. Proceedings of the National Academy of Sciences USA 98:7875-7878.
Bloom AJ, Smart DR, Nguyen DT, Searles PS (2002) Nitrogen assimilation and growth of wheat under elevated carbon dioxide. Proceedings of the National Academy of Sciences USA 99:1730-1735.
Bloom AJ (2002) Chapter 5. Mineral Nutrition. In: Taiz L, Zeiger E (eds) Plant Physiology, 3rd Edition. Sinauer Assoc., Sunderland, MA, pp 67-86.
Bloom AJ (2002) Chapter 12. Assimilation of Mineral Nutrients. In: Taiz L, Zeiger E (eds) Plant Physiology, 3rd Edition. Sinauer Assoc., Sunderland, MA, pp 259-282.
Bloom AJ, Meyerhoff PA, Taylor AR, Rost TL (2002) Root development and absorption of ammonium and nitrate from the rhizosphere. J Plant Growth Regulation 21:416-431.
Bloom AJ, Rost TL (2002) Root structure and function. Journal of Plant Growth Regulation 21:245-246.
Gutschick V.P. & Bloom A.J. (2003) Crossroads of animal, plant, and microbial physiological ecology. BioSciences 53:256-259.
Searles PS, Bloom AJ (2003) Nitrate photoassimilation in tomato leaves under short-term exposure to elevated carbon dioxide and low oxygen. Plant Cell & Environment 26: 1247-1255.
Cousins AB, Bloom AJ (2003) Influence of elevated CO2 and nitrogen nutrition on photosynthesis and nitrate photoassimilation in maize (Zea mays L.). Plant Cell & Environment 26: 1525-1530.
Bloom AJ, Zwieniecki MA, Passioura JB, Randall LB, Holbrook NM, St. Clair DA (2004) Water relations under root chilling in a sensitive and tolerant tomato species. Plant Cell & Environment 27:971-979.
Rachmilevitch S, Cousins AB, Bloom AJ (2004) Nitrate assimilation in plant shoots depends on photorespiration. Proceedings of the National Academy of Sciences USA 101:11506-11510.
Cousins AB, Bloom AJ (2004) Oxygen consumption during leaf nitrate assimilation in a C3 and C4 plant: the role of mitochondrial respiration. Plant Cell & Environment 27:1537-1545.
Epstein E, Bloom AJ (2005) Mineral Nutrition of Plants: Principles and Perspectives. 2nd Edition. Sinauer Associates, Sunderland, MA, 405 pp.
Volder A, Smart DR, Bloom AJ, Eissenstat DM (2005) Rapid decline in nitrate uptake and respiration with age in fine lateral roots of grape: implications for root efficiency and competitive effectiveness. New Phytologist 165:493-501.
Bloom AJ (2005) Coordination between roots and shoots. In NM Holbrook, MA Zwieniecki, eds, Long-Distance Transport in Plants. Academic Press, San Diego, CA, pp 241-256.
Goodstal FJ, Kohler GR, Randall LB, Bloom AJ, St. Clair DA (2005) A major QTL introgressed from wild Lycopersicon hirsutum confers chilling tolerance to cultivated tomato (Lycopersicon esculentum). Theoretical and Applied Genetics: 111:898-905
Bloom AJ (2006) Chapter 5. Mineral Nutrition. In: Taiz L, Zeiger E (eds) Plant Physiology, 4th Edition. Sinauer Assoc., Sunderland, MA.
Bloom AJ (2006) Chapter 12. Assimilation of Mineral Nutrients. In: Taiz L, Zeiger E (eds) Plant Physiology, 4th Edition. Sinauer Assoc., Sunderland, MA.
Bloom AJ, Frensch J, Taylor AR (2006) Influence of inorganic nitrogen and pH on the elongation of maize seminal roots. Annals of Botany 97:867-873.
Rost TL, Bloom AJ (2006) Root structure and function. Annals of Botany 97:837-838.
Bloom AJ (2006) Rising carbon dioxide concentrations and the future of crop production. Journal of the Science of Food and Agriculture 86:1289-1291.
Bloom AJ (2009) Responses of crop plants to rising atmospheric carbon dioxide concentrations. California Agriculture 63:67-72.
Foyer CH, Bloom AJ, Queval G, Noctor G (2009) Photorespiratory metabolism: genes, mutants, energetics, and redox signaling. Annual Review of Plant Biology 60:455-484.
Volder A, Anderson LJ, Smart DR, Bloom AJ, Lakso AN, Eissenstat DM (2009) Estimating nitrogen uptake of individual roots in container- and field-grown plants using a 15N-depletion approach. Functional Plant Biology 36:621-628.
Bloom AJ (2010) Global Climate Change: Convergence of Disciplines. Sinauer Assoc., Sunderland, MA, 420 pp.
Bloom AJ (2010) Chapter 5. Mineral Nutrition. In: Taiz L, Zeiger E (eds) Plant Physiology, 5th Edition. Sinauer Assoc., Sunderland, MA. pp. 107-130.
Bloom AJ (2010) Chapter 12. Assimilation of Mineral Nutrients. In: Taiz L, Zeiger E (eds) Plant Physiology, 5th Edition. Sinauer Assoc., Sunderland, MA. pp. 341-368.
Bloom AJ, Burger M, Asensio JSR, Cousins AB (2010) Carbon dioxide enrichment inhibits nitrate assimilation in wheat and Arabidopsis. Science 328: 899-903.
Bloom AJ (2010) Energetics of nitrogen acquisition. In: Foyer C, Zhang H (eds) Nitrogen Metabolism plants in the Post-Genomic Era. Vol. 2: Whole plant perspectives of nitrogen metabolism and network signalling processes in plants. Blackwell, Chichester UK, pp. 63-82.
Bloom AJ, Asensio JSR, Randall L, Rachmilevitch S, Cousins AB, Carlisle EA (2012) CO2 enrichment inhibits shoot nitrate assimilation in C3 but not C4 plants and slows growth under nitrate in C3 plants. Ecology 93:355-367.
Bloom AJ, Randall L, Taylor AR, Silk WK (2012) Deposition of ammonium and nitrate in the roots of maize seedlings supplied with different nitrogen salts. Journal of Experimental Botany 63:1997-2006.
Bloom AJ (2012) Integrated whole organism physiology. In: Hastings A, Gross L (eds) Encyclopedia of Theoretical Ecology. UC Press, Berkeley, CA, pp. 376-381.
Return to top