Portland State University. Department of Biology
Date of Award
Doctor of Philosophy (Ph.D.) in Biology
1 online resource (x, 259 pages)
Our first aim was to identify and quantify Biological Volatile Organic Compound (BVOC) emissions, specifically emissions of isoprene, from the moss Polytrichum juniperinum during its earliest stage of life. Isoprene emission from mosses could be a significant component of the total global budget of BVOC emissions. Data concerning the spatial and temporal variability of these emissions are lacking due to poor characterization of the physical and biological factors controlling isoprene synthesis in both vascular and non-vascular plants. We found that P. juniperinum in its early life stage (protonema) can emit isoprene at detectable levels at day five after spore germination. These results suggest that protonema is capable of isoprene emission, shown here for the first time, and media affects emission rates. We saw a negative trend with leaf emergence and protonema growth. Chlorophyll fluorescence ratio had a positive correlation with isoprene emission, and isoprene emission was both temperature and light dependent in early protonema.
Our second aim was to determine the effects of sex and sexual expression on isoprene emission in mosses. Sex is a biologically costly, but it can result in genetic adaptability and variety for resulting offspring. Using three Polytrichaceae species, we measured isoprene emission between plants sexually expressing and non-expressing and between male and female moss plants. We found that non-sexually expressing gametophytes had significantly higher isoprene emission than gametophytes expressing sex, suggesting that sex expression may be costly and that additional resources are allocated to isoprene emission when plants are not reproducing. Males emitted higher levels of isoprene than females, but surprisingly this difference occurred only when plants were not expressing sex. We found species and sex-specific differences in chlorophyll fluorescence ratio (CFR) and relative electron transport rate (RETR).
Our third aim was to investigate and categorize the effect of nitrogen addition on isoprene emission of P. juniperinum by creating an artificial nitrogen gradient with ammonium nitrate addition (NH4NO3). Current rates of anthropogenic N deposition are altering many biogeochemical processes. In these changing environments, increased nitrogen availability alters plant phenology, physiology, and the allocation of resources, but no information is available on whether additional N increases isoprene emissions in mosses. We used a manipulative experiment to measure the effects of nitrogen addition on moss isoprene emission, as well as on moss morphology and reproductive effort. We found site-specific differences in our morphological and physiological measurements. Isoprene emission was site, sex, and N addition specific, with the highest isoprene emission seen from our mid-level N addition, in both female- and male-majority pots. We found significant treatment and sex-specific interactions among our sites and within sites. We saw the highest reproductive effort counts from non-sexual expressive gametophytes, followed by high sporophyte count from female-majority pots. We also saw chlorophyll fluorescence ratio (CFR) differences between sites and treatments, but not between sexes.
Deakova, Timea, "Isoprene Emission in Polytrichaceae Mosses" (2019). Dissertations and Theses. Paper 4984.