Plant traits, such as root and leaf area, influence how plants interact with their environment and the diverse microbiota living within plants can influence plant morphology and physiology. Here, we explored how three bacterial strains isolated from the Populus root microbiome, influenced plant phenotype. We chose three bacterial strains that differed in predicted metabolic capabilities, plant hormone production and metabolism, and secondary metabolite synthesis. We inoculated each bacterial strain on a single genotype of Populus trichocarpa and measured the response of plant growth related traits (root:shoot, biomass production, root and leaf growth rates) and physiological traits (chlorophyll content, net photosynthesis, net photosynthesis at saturating light-Asat, and saturating CO2-Amax). Overall, we found that bacterial root endophyte infection increased root growth rate up to 184% and leaf growth rate up to 137% relative to non-inoculated control plants, evidence that plants respond to bacteria by modifying morphology. However, endophyte inoculation had no influence on total plant biomass and photosynthetic traits (net photosynthesis, chlorophyll content). In sum, bacterial inoculation did not significantly increase plant carbon fixation and biomass, but their presence altered where and how carbon was being allocated in the plant host.
Bibliographical noteFunding Information:
We thank Lee Gunter, Tse-Yuan Lu, Kelsey Carter, Jesse Labbe, and W. Nathan Cude for their assistance in data collection and plant propagation. The Classen Ecosystem Ecology group and three reviewers provided valuable input on earlier reviews of this manuscript. 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. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.
- Bacterial endophytes
- Plant functional traits
- Plant morphology
- Populus trichocarpa
- Pseudomonas fluorescens
- Trait plasticity