Presentation Title

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

Faculty Mentor

Stephen D. Davis

Start Date

18-11-2017 12:30 PM

End Date

18-11-2017 1:30 PM

Location

BSC-Ursa Minor 52

Session

Poster 2

Type of Presentation

Poster

Subject Area

biological_agricultural_sciences

Abstract

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.

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Nov 18th, 12:30 PM Nov 18th, 1:30 PM

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

BSC-Ursa Minor 52

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.