Presentation Type
Poster
Keywords
climate change, pathology, Laural Sumac, chaparral, fungi, water potential, hydraulic conductance
Department
Biology
Major
Biology
Abstract
Between 2012-2016, southern California experienced unprecedented drought that caused dieback in Malosma laurina, a keystone species of chaparral shrub communities. Dieback was especially severe in coastal exposures of the Santa Monica Mountains, leading to whole plant mortality exceeding 50% at some sites. We hypothesized that the endophytic fungus causing the dieback, Botryosphaeria dothidea, was successful in invading the xylem tissue of M. laurina because of protracted water stress, carbon starvation, or a combination of the two. We tested these possibilities in a controlled pot experiment by comparing three treatments, each inoculated with the fungus: (1) irrigated controls (2) non-irrigated (water stressed) plants and (3) carbon starved plants. We also compared the tissue dehydration limits of the chaparral host (M. laurina) to the fungal pathogen (B. dothedia) on culture media and living stem segments in the lab. Fungal elongation rates in xylem tissue of potted plants continued in all treatments over an eight-week period but were over two fold greater in water stressed plants than irrigated controls, leading to increased incidence of whole branch dieback. Minimum water potentials at the time of whole plant death and vulnerability to water stress-induced embolism of xylem conduits indicated that the host plant could not survive water potentials more negative than – 4 MPa. Stem segments in the lab at decreasing water potentials indicated continued rapid fugal elongation well below -4 MPa. These results were consistent with field observations of fungal blockage in water transport of xylem leading to branch dieback and eventual whole plant mortality.
Faculty Mentor
Dr. Stephen D. Davis
Funding Source or Research Program
Not Identified
Location
Waves Cafeteria
Start Date
24-3-2017 2:00 PM
End Date
24-3-2017 3:00 PM
Hydraulic Mechanisms of Fungal-Induced Dieback in a Keystone Chaparral Species during Unprecedented Drought in California
Waves Cafeteria
Between 2012-2016, southern California experienced unprecedented drought that caused dieback in Malosma laurina, a keystone species of chaparral shrub communities. Dieback was especially severe in coastal exposures of the Santa Monica Mountains, leading to whole plant mortality exceeding 50% at some sites. We hypothesized that the endophytic fungus causing the dieback, Botryosphaeria dothidea, was successful in invading the xylem tissue of M. laurina because of protracted water stress, carbon starvation, or a combination of the two. We tested these possibilities in a controlled pot experiment by comparing three treatments, each inoculated with the fungus: (1) irrigated controls (2) non-irrigated (water stressed) plants and (3) carbon starved plants. We also compared the tissue dehydration limits of the chaparral host (M. laurina) to the fungal pathogen (B. dothedia) on culture media and living stem segments in the lab. Fungal elongation rates in xylem tissue of potted plants continued in all treatments over an eight-week period but were over two fold greater in water stressed plants than irrigated controls, leading to increased incidence of whole branch dieback. Minimum water potentials at the time of whole plant death and vulnerability to water stress-induced embolism of xylem conduits indicated that the host plant could not survive water potentials more negative than – 4 MPa. Stem segments in the lab at decreasing water potentials indicated continued rapid fugal elongation well below -4 MPa. These results were consistent with field observations of fungal blockage in water transport of xylem leading to branch dieback and eventual whole plant mortality.