Page 275 - PC2019 Program & Proceedings

PLANT CANADA 2019

P123. The interaction of marine phytoplankton cell size with capacities for reactive oxygen
detoxification
*
Rehman, A. ; D. Campbell
Mount Allison University

Production of reactive oxygen species (ROS) accompanies stress conditions in photosynthetic organisms
1
including marine phytoplankton . The ROS include hydrogen peroxide (H2O2), superoxide anion radical,
hydroxyl radical and singlet oxygen, each with characteristic lifetimes and subject to different scavenging
processes. We hypothesized that phytoplankton cell size interacts with light stress through influences on
intra- and extracellular ROS accumulation. We, therefore, used fluorescent probes to examine cell size
dependencies of detoxification capabilities and susceptibilities to externally supplied and internally
generated ROS in five centric diatoms ranging from Minidiscus variabilis (3 µm diameter) to
Coscinodiscus wailesii (300 µm diameter). Externally supplied 100 µM H2O2 provoked a 10-fold
increase in intracellular H2O2, leading to significant decreases in PSII activity in larger, but not in
smaller, diatom cultures. The resistance of the smaller diatoms is largely explicable through greater
detoxification of H2O2 in dense cultures vs. lower density suspensions of the larger cells. Therefore,
population or community level cooperative detoxification capacities are important to cellular level
responses to ROS. We give an overview of results using fluorescence probes to track specific ROS
accumulations in phytoplankton of different cell sizes.

1. Diaz, J. M. & Plummer, S. Production of extracellular reactive oxygen species by phytoplankton: past
and future directions. Journal of Plankton Research (2018). doi:10.1093/plankt/fby039

Ateeq Ur Rehman (ateeq283@gmail.com)

P124. Assessing threats and mitigation for Scarlet Ammannia (Ammannia robusta) in Southwestern
Ontario
*
Salive, K. ; M. Costea; K. Stevens
Wilfrid Laurier University

Scarlet Ammannia (Ammannia robusta) is an annual emergent wetland plant of the Lythraceae family.
Throughout most of its global distribution the species population is stable under present conditions.
However, in Canada, A. robusta is considered endangered with only a few small populations documented
in British Columbia and Ontario. In response, a recovery strategy was created for A. robusta outlining the
lack of information on the species biology and ecology. Field vegetation surveys and seed bank assays
were conducted to assess the current status of A. robusta in Southwestern Ontario (Pelee Island). Results
show that although the species may not be present during field vegetation surveys in a certain area, it is
present in the areas seed bank. Therefore, limiting factors will be examined to further understand why this
pattern is occurring. Both field and greenhouse studies will be conducted with and without the presence of
competitors to assess the effects of competitor removal on A. robusta. Additionally, A. robusta seeds will
be used to conduct germination trials to fill in knowledge gaps pertaining to the influence of light
duration, light intensity and temperature requirements. By examining these factors, I plan to verify what is
limiting the distribution of A. robusta in Southwestern Ontario in order to establish conservation efforts
that will improve the species distribution in Canada.

Kayla Salive (kaylasalive@gmail.com)

Page 273 of 339