Presentation Title

A Comparison of Water Potential, Photosynthetic Rate, Electron Transport Rate, and Stomatal Conductance between Native Malosma laurina and Exotic Schinus molle

Presentation Type

Poster

Department

Biology

Major

Biology

Abstract

A Comparison of Water Potential, Photosynthetic Rate, Electron Transport Rate, and Stomatal Conductance between Native Malosma laurina and Exotic Schinus molle

Karagan L. Smith, Agatha C. Heng, and Viridiana Hernandez-Lopez

First-year Students as Scholars Program

Mentors: Natalie M. Aguirre, Kaitlyn E. Sauer, and Stephen D. Davis

Schinus molle is a relatively new invasive species in chaparral shrub communities of the Santa Monica Mountains, and has only recently been observed to displace native species of shrubs, such as Malosma laurina. To investigate the probably cause of S. molle’s invasiveness and mechanisms of competitive displacement of M. laurina, we compared their water status, photosynthetic rates, electron transport rates, and stomatal conductance to water vapor diffusion during the unusually dry fall of 2016. We used a Scholander-Hammel pressure chamber to measure water status and a field portably gas-exchange system to measure light and dark reaction components of photosynthesis, concurrent with stomatal conductance (LI-6400XT). We hypothesized that S. molle would physiologically outperform M. laurina, under natural field conditions, indicated by higher photosynthetic rates, electron transport rates, and stomatal conductance rates as well as a less negative water potentials (higher water status). We found that there was no significant difference between dry S. molle and dry M. laurina regarding photosynthetic rates; however the stomatal conductance of S. molle was significantly lower than M. laurina, indicating higher water use efficiency (greater carbon gain for the amount of water lost). The electron transport rate (ETR) was significantly higher for S. molle than M. laurina, suggesting more efficient conversion of light energy to chemical energy in the light reaction of photosynthesis. These results suggest that S. molle has a physiological advantage over M. laurina in greater efficiency in water use as well as greater efficiency in radiant energy conversion. Both of these factors may contribute to S. molle’s ability to aggressively outcompete M. laurina, especially during periods of extreme drought. Invasiveness and competitive exclusion of native species by S. molle may be enhanced by a gradual increase in a hotter and drier climate in California.

Faculty Mentor

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

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Mar 24th, 2:00 PM Mar 24th, 3:00 PM

A Comparison of Water Potential, Photosynthetic Rate, Electron Transport Rate, and Stomatal Conductance between Native Malosma laurina and Exotic Schinus molle

Waves Cafeteria

A Comparison of Water Potential, Photosynthetic Rate, Electron Transport Rate, and Stomatal Conductance between Native Malosma laurina and Exotic Schinus molle

Karagan L. Smith, Agatha C. Heng, and Viridiana Hernandez-Lopez

First-year Students as Scholars Program

Mentors: Natalie M. Aguirre, Kaitlyn E. Sauer, and Stephen D. Davis

Schinus molle is a relatively new invasive species in chaparral shrub communities of the Santa Monica Mountains, and has only recently been observed to displace native species of shrubs, such as Malosma laurina. To investigate the probably cause of S. molle’s invasiveness and mechanisms of competitive displacement of M. laurina, we compared their water status, photosynthetic rates, electron transport rates, and stomatal conductance to water vapor diffusion during the unusually dry fall of 2016. We used a Scholander-Hammel pressure chamber to measure water status and a field portably gas-exchange system to measure light and dark reaction components of photosynthesis, concurrent with stomatal conductance (LI-6400XT). We hypothesized that S. molle would physiologically outperform M. laurina, under natural field conditions, indicated by higher photosynthetic rates, electron transport rates, and stomatal conductance rates as well as a less negative water potentials (higher water status). We found that there was no significant difference between dry S. molle and dry M. laurina regarding photosynthetic rates; however the stomatal conductance of S. molle was significantly lower than M. laurina, indicating higher water use efficiency (greater carbon gain for the amount of water lost). The electron transport rate (ETR) was significantly higher for S. molle than M. laurina, suggesting more efficient conversion of light energy to chemical energy in the light reaction of photosynthesis. These results suggest that S. molle has a physiological advantage over M. laurina in greater efficiency in water use as well as greater efficiency in radiant energy conversion. Both of these factors may contribute to S. molle’s ability to aggressively outcompete M. laurina, especially during periods of extreme drought. Invasiveness and competitive exclusion of native species by S. molle may be enhanced by a gradual increase in a hotter and drier climate in California.