C.R. HowellOctober Measuring Dynamical Responses of Plants to Environment Change Using Short-lived Radioisotope Calvin Howell Duke University Physics Triangle Universities Nuclear Laboratory

C.R. HowellOctober C.R. Howell (Physics) C. Reid (Biology) E. Bernhardt (Biology) A.S. Crowell (Physics Postdoc) M. Kiser (Physics graduate student) R. Phillips (Biology Postdoc) Measuring Dynamic Biological Responses in Plants using Radioisotopes Collaboration

C.R. HowellOctober What is a Phytotron? CEFControlled Environment Facility Growth chambers can control many factors: –Soil type –Air Temperature –Light levels (total & UV) –Carbon dioxide concentration –Relative humidity –Nutrients –Air pollutants

C.R. HowellOctober Evidence for Influence of Human Activities on Atmospheric CO2 Levels “Industrial Revolution”

C.R. HowellOctober Long timeline Atmospheric CO2 Levels

C.R. HowellOctober The Vostok Station in Antarctica Information: The coldest recorded temperature on Earth, °F (-89.2°C) was measured here on July 21, Latitude/Longitude: 78°27'51"S 106°51'57"E Altitude: ft3 (500 m) above sea level Average Annual Temperature: -67°F (-55°C)

C.R. HowellOctober Ice Core Measurements at Vostok

C.R. HowellOctober Atmospheric CO2 Concentration Measurements Since the 1950’s Mauna Loa Observatory (MLO) is an atmospheric baseline station. Since the mid 1950's MLO has been continuously monitoring and collecting data relating to atmospheric change. The observatory is under the Earth System Research Laboratory (ESRL) - Global Monitoring Division (GMD) which is part of the National Oceanic and Atmospheric Administration (NOAA).Earth System Research Laboratory (ESRL) Global Monitoring Division (GMD)National Oceanic and Atmospheric Administration (NOAA)

C.R. HowellOctober Recent Atmospheric CO2 Concentration Data

C.R. HowellOctober Carbon Budget Sinks in units of billions of metric tons of carbon (GtC) Fluxes in units of billions of metric tons of carbon per year (GtC/year) Intergovernmental Panel on Climate Change (IPCC): Climate Change 2001, “The Carbon Cycle and Atmospheric Carbon Dioxide”

C.R. HowellOctober Carbon Budget Sinks in units of billions of metric tons of carbon (GtC) Fluxes in units of billions of metric tons of carbon per year (GtC/year) Intergovernmental Panel on Climate Change (IPCC): Climate Change 2001, “The Carbon Cycle and Atmospheric Carbon Dioxide”

C.R. HowellOctober Interesting Aside Total tonnage of CO 2 produced by vehicles over 124,000 mile lifetime Assuming ~10 year lifetime, vehicles emit more than their own weight in CO 2 per year 13 mpg 36 mpg 22 mpg 18 mpg 65 mpg Top 5 CO 2 Emitters: 1. U.S. 2. China 3. Russia 4. Japan 5. U.S. autos

C.R. HowellOctober Motivations Intergovernmental Panel on Climate Change (IPCC): Climate Change 2001, “The Carbon Cycle and Atmospheric Carbon Dioxide” Climate models predict atmospheric CO 2 levels will double by the end of this century! How will plants respond?

C.R. HowellOctober FACE Studies Free Air CO 2 Enrichment (FACE) experiments –Large-scale research programs to study effects of increased CO 2 levels –Many environmental variables –Difficult to correlate growth parameters with high precision Findings from forest stands –Initially, trees grow faster in CO 2 enhanced environment, but then grow a slower rate than trees grown in at ambient CO 2 level Duke FACTS-I Aerial View

C.R. HowellOctober FACE Sites

C.R. HowellOctober Introduction to Plant Studies with Radioisotopes 14 C used in mid-1940’s –Long half-life (~5730 years) –Weak beta emitter –Tracer measured by destructive harvesting Use of 11 C for in vivo studies demonstrated in – More and Troughton at the Department of Scientific and Industrial Research in New Zealand showed that useful amounts of 11 C can be produced using small van de Graaf accelerators –Labs in USA, Canada, Scotland, New Zealand, and Germany start using 11 C for mechanistic studies of photosynthate transport in the mid 1970’s –Present studies at: Julich, Germany; Univ. Tokyo; BNL; TUNL-Duke

C.R. HowellOctober Planned Research at the TUNL-Phytotron Facility 1.Studies of CO 2 uptake and carbon translation under different environmental conditions 2.Root exudate measurements 3.Nutrient uptake and translocation under different environmental conditions

C.R. HowellOctober Plant Physiology 101 a) Sugars loaded into a sieve tube b) Loading of the phloem sets up water potential gradient that facilitates movement of water into dense phloem sap from the neighboring xylem c) As hydrostatic pressure in phloem sieve tube increases, pressure flow begins, and sap moves through the phloem d) At the sink, incoming sugars actively transported out of phloem and removed as complex carbohydrates e) Loss of solute produces high water potential in phloem, and water passes out, returning eventually to xylem

C.R. HowellOctober Carbon-11 Production p + 14 N  11 C +  Produce H - ions in negative ion source 4 5 Accelerate H - ions toward +5MV terminal Strip off electrons with carbon foil (H -  p) Accelerate protons away from +5MV terminal Bend p in magnet and collide on 14 N target

C.R. HowellOctober Radioisotope Production CO 2 (half life = 20 min.) 14 N + p  11 C +  Target: gas F - (half life = 109 min.) 18 O + p  18 F + n Target: 18 O enriched water NO 3 - (half live = 10 min.) 16 O + p  13 N +  Target: 18 O depleted water 4. H 2 18 O (half life = 2 min.) 16 O + p  15 O + d Target: water

C.R. HowellOctober Single Detector Measurements Use detectors collimated for specific areas of plant to trace carbon allocation on a coarse (source/sink) scale Develop quantitative flow models to describe dynamics

C.R. HowellOctober Single Detector Measurements

C.R. HowellOctober Statistical Model Extract Physically Significant Quantities: (1)Gaininputoutput (1)Gain – fraction of input that shows up at the output (2)Average transit time Discrete observation times: t k where k = 0, 1, 2, … Y k = counts in Sink B at time t k (output) U k = counts in Total Sink at time t k (input) Y k = - a 1 Y k-1 - a 2 Y k-2 - … - a n Y k-n + b 0 U k + b 1 U k-1 + … + b m U k-m Leaf Shoot Root Source Total Sink Sink A Sink B respiration respiration, exudation

C.R. HowellOctober D Imaging

C.R. HowellOctober For Example x (cm) y (cm)

C.R. HowellOctober For Example x (cm) y (cm)

C.R. HowellOctober Immediate Plans Develop system for continuous loading measurements Develop system for nutrient uptake studies Continue root exudate experiments Develop high-resolution 2D PET imager

C.R. HowellOctober High resolution 2D imagers 5 cm x 5 cm x 1.5 cm 2mm x 2mm pixels (0.1 mm gap) 20 cm x 30 cm field of view