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PI-Submitted Research Highlights for
Terrestrial Ecosystem Science Program

Bacteria Living Within Plant Roots Affect Where and How Plants Allocate Carbon for Growth

Aimee T. Classen
University of Vermont

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14 February 2017
Bacteria living within plant root tissues influence the size and shape of plant leaves and roots and how plants allocate carbon toward leaves, stems, or roots.

The Science
Plant traits, such as root and leaf area, influence how plants interact with their environment, and bacteria living within plant tissues can determine morphology (their form and structure) and physiology (how they function). To understand how different microbes shaped plant morphology and physiology, we inoculated cottonwood seedlings with three different strains of root-dwelling bacteria. We found the bacteria did not change photosynthesis rates or total biomass, but bacteria regulated where carbon was allocated and how plants used it. Additionally, we found closely related bacteria can have very different effects on plant growth.

The Impact
Since plants interact with their environments through their traits, bacteria may be an important middle-man determining how plants will respond to changing environmental conditions.

Summary
Bacteria living within plant tissues (endophytes) can change how plants express traits such as root and leaf growth rates, and the ratio of root to leaves. Small changes in these traits could build up to alter how plants survive, adapt, and compete within their environment. We either inoculated cottonwood seedlings with one of three endophytic bacterial stains, or left the plant un-inoculated as a control, and then looked at several responses including root and leaf growth rate, plant biomass, photosynthetic rate, and the ratio of roots to leaves. We found inoculation was linked to an increase in root and leaf growth rate, but that this increase in growth rate did not lead to an increase in plant biomass or photosynthetic efficiency. These findings indicate bacterial endophytes can change where and how carbon is used in a plant, but may not increase the overall amount of carbon fixed by photosynthesis and stored in the plant’s biomass.

Contacts (BER PM)
Daniel Stover
SC-23.1
Daniel.Stover@science.doe.gov (301-903-0289)

(PI Contact)
Aimee T. Classen
University of Vermont
Aimee.Classen@uvm.edu

Funding
Funding from Plant-Microbe Interfaces Scientific Focus Area project at Oak Ridge National Laboratory was provided by the U.S. DOE Office of Biological and Environmental Research, Genomic Science Program. Oak Ridge National Laboratory is managed by UT-Battelle, LLC, for the US Department of Energy under contract no. DEAC05-00OR22725. JH was supported, in part, by the U.S. Department of Energy, Office of Science, Office of Biological and Environmental Research, Terrestrial Ecosystem Sciences Program under Award Number DE-SC0010562.

Publications
J. Henning et al., “Root bacterial endophytes alter plant phenotype, but not physiology.” PeerJ 4:e 2606 (2016)


Jeremiah Henning (the lead author) took this picture. 

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