Watching Carbon Dioxide Move in Plant Leaves

The Science

U.S. Department of Energy (DOE) plant biology research seeks to optimize plant productivity, both for biofuel development and for carbon sequestration in biomass. Taking a lesson from medical technology, plant biologists are now using sophisticated imaging technology to learn more about nutrient utilization in plants by watching the movement of those nutrients in real time. Positron emission tomography (PET) imaging has been used to study carbon transport in live plants using ¹¹CO₂, but because plants typically have very thin leaves, little medium is available for the emitted positrons to undergo an annihilation event within the plant leaf resulting in limited sensitivity for PET imaging.

To address this problem DOE’s Thomas Jefferson Laboratory has developed a compact beta-positive, beta-minus particle imager (PhytoBeta imager) for ¹¹CO₂ leaf imaging. The detector is equipped with a flexible arm to allow its placement on or under a leaf while maintaining its original orientation. The detector has been used to generate dynamic images of carbon translocation in a leaf of the spicebush (Lindera benzoin) under two transient light conditions. The PhytoBeta detector system and methodology opens new possibilities for short-lived radioisotope use in plant biology research, especially for problems related to carbon utilization, transport, and sequestration. In order to study plant physiological processes it is important to minimize physical disturbance to the plant and minimize the blocking of light incident on the leaf surface. For imaging carbon uptake and transport in the plant leaf, the ¹¹C detection methodology needs to minimize shading of the leaf and not affect the leaf orientation or its boundary layer resistance.

References

Weisenberger, A. G., B. Kross, S. Lee, J. McKisson, J. E. McKisson, W. Xi, C. Zorn, C. D. Reid, C. R. Howell, A. S. Crowell, L. Cumberbatch, B. Fallin, A. Stolin, and M. F. Smith. 2012. “PhytoBeta Imager: A Positron Imager for Plant Biology,” Physics in Medicine and Biology 57(13), 4195–210. DOI: 10.1088/0031-9155/57/13/4195.