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Abstract Detail


Palmeri, Gabriella [1], Reese, Shaquetta [1], Holmlund, Helen [2], Ewers, Frank [3], Davis, Stephen Darrel [4].

Malosma laurina Dieback Associated with Fungal-induced Loss in Hydraulic Conductivity and Photosynthesis.

A widespread keystone species, Malosma laurina, is experiencing severe dieback throughout the Santa Monica Mountains (SMM) of southern California. M. laurina has nearly 100% post-fire resprout success, and its deep roots provide necessary slope stability to the hillsides; therefore, M. laurina’s health is of ecological importance. Since water is a determinant of plant growth and survival in dry environments, our research examined whether M. laurina dieback is associated with decreased stem water transport due to the prevalence of a pathogenic fungus within the water transport tissue. In addition to hydraulic conductivity, we measured dieback plant water potential, photosynthetic rate, and transpiration rate in comparison to healthy controls. Xylem tissues from dieback and healthy controls were aseptically transferred to Potato Dextrose Agar for the cultivation of fungi. Nearly 100% of samples from stem xylem of dieback plants contained the fungal pathogen Botryosphaeria dothidea, whereas 0% of adult healthy plants contained the pathogen (n = 20). The hydraulic conductivity (Kh) and specific conductivity per unit xylem area (Ks) were significantly lower in dieback M. laurina both for adults (0.503 mg • mm-1 • s-1 • kPa-1) and resprouts (0.235 mg • mm-1 • s-1 • kPa-1 ) compared to healthy controls (3.31 and 2.67 mg • mm-1 • s-1 • kPa-1 respectively). Midday water potentials were significantly lower for dieback plants than control plants, consistent with our fungal isolation results and the hypothesis that severe drought in southern California predisposes M. laurina to fungal infection. Double staining of dieback and control M. laurina xylem suggested that a physical blockage of vessels caused the observed decrease in stem water transport. Continued dieback of M. laurina will likely provide an opportunity for invasion of non-native weeds that may lead to a decrease in slope stability and an increase in fire frequency within the Santa Monica Mountains. Within the context of continued drought in southern California and global climate change, the need to preserve native biodiversity, especially keystone species, is apparent.

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1 - Pepperdine University, Natural Science, 24255 Pacific Coast Highway, Malibu, CA, 90263, USA
2 - University of California, Santa Cruz, Ecology and Evolutionary Biology, 1156 High Street, Santa Cruz, CA, 95064, USA
3 - California State Polytechnic University, Pomona, 3801 West Temple Avenue, Pomona, CA, 91768, USA
4 - PEPPERDINE UNIVERSITY, NATURAL SCIENCE DIV, 24255 Pacific Coast Highway, MALIBU, CA, 90263-4321, USA

Malosma laurina
hydraulic conductivity
fungal-induced dieback
Botryosphaeria dothidea.

Presentation Type: Poster
Session: P, Ecophysiology Poster Session
Location: Exhibit Hall/Savannah International Trade and Convention Center
Date: Monday, August 1st, 2016
Time: 5:30 PM This poster will be presented at 5:30 pm. The Poster Session runs from 5:30 pm to 7:00 pm. Posters with odd poster numbers are presented at 5:30 pm, and posters with even poster numbers are presented at 6:15 pm.
Number: PEP003
Abstract ID:261
Candidate for Awards:Physiological Section Best poster presentation,Physiological Section Physiological Section Li-COR Prize

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