Portland State University. Department of Biology
Sarah M. Eppley
Date of Award
Master of Science (M.S.) in Biology
1 online resource (vi, 63 pages)
The microorganisms colonizing plants can have a significant effect on host phenotype, mediating such processes as pathogen resistance, stress tolerance, nutrient acquisition, growth, and reproduction. Research regarding plant-microbe interactions has focused almost exclusively on vascular plants, and we know comparatively little about how bryophytes -- including mosses, liverworts, and hornworts -- are influenced by their microbiomes. Ceratodon purpureus is a dioecious, cosmopolitan moss species that exhibits sex-specific fungal communities, yet we do not know whether these microbes have a differential effect on the growth and physiology of male and female genotypes. Using a common-garden design, we reared ten axenic genotypes of C. purpureus in a controlled environmental chamber. Clonal C. purpureus replicates, with and without the addition of a microbial inoculation, were used to test the effect of a mixed microbial community on vegetative growth, sex expression, photosynthetic efficiency (Fv/Fm and ETR), and chlorophyll content (CFR) for male and female mosses. We found that microbes had a negative impact on the growth and photosynthesis efficiency of C. purpureus, and this effect varied among genotypes of C. purpureus for ETR and growth. Microbes also had a positive, sex-specific effect on chlorophyll content in C. purpureus, with males exhibiting lower CFR values in the absence of microbes. C. purpureus sex expression was marginally negatively affected by microbe addition, but gametangia production was low overall in our experiment. We also conducted preliminary surveys using direct counts from moss ramets to assess the community composition of epiphytic algae associated with our microbe addition and control C. purpureus. These surveys identified three algal morphospecies in association with the microbe addition C. purpureus genotypes, as well as cyanobacteria, nematodes, rotifers, and testate amoeba. No algae, cyanobacteria, or micro-fauna were observed in the control plants. Transplantation of a mixed microbial community from field-to-laboratory conditions may be applied to other bryophyte species under varying environmental conditions to provide insight into how these diminutive yet important ecosystems will respond to environmental perturbation.
Maraist, Caitlin Ann, "Effect of Microbes on the Growth and Physiology of the Dioecious Moss, Ceratodon purpureus" (2018). Dissertations and Theses. Paper 4353.
Available for download on Saturday, March 23, 2019