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

Bacteria within plant root tissues influence the size and shape of plant leaves and roots, as well as 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 how bacteria living within plant tissues can determine morphology (plant form and structure) and physiology (how they function). To understand how different microbes shaped plant morphology and physiology, researchers inoculated cottonwood seedlings with three different strains of root-dwelling bacteria. They found that the bacteria did not change photosynthesis rates or total biomass, but bacteria regulated where carbon was allocated and how plants used it. Additionally, the researchers found closely related bacteria can have vastly different effects on plant growth.

The Impact

Since plants interact with their environment through their traits, bacteria may be an important middleman in determining how plants will respond to changing environmental conditions.


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. In a recent study, researchers either inoculated cottonwood seedlings with one of three endophytic bacterial stains or left the plant un-inoculated as a control. They then looked at several responses including root and leaf growth rate, plant biomass, photosynthetic rate, and the ratio of roots to leaves. They found that 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.

Principal Investigator(s)

Aimee Classen
University of Vermont


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


Henning, J., et al. “Root bacterial endophytes alter plant phenotype, but not physiology.” PeerJ 4, e2606 (2016). DOI:10.7717/peerj.2606