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Who Turned Up the Heat? Floral Responses to Heatwaves in the Oilseed Camelina sativa
Cameron P. So, Sarah Hall, Sophia Fan, and Arthur Weis
Department of Ecology and Evolutionary Biology, University of Toronto
Background
• Heatwaves are increasing in frequency, length, and
intensity due to climate change1.
Daily Flower Production
Figure 2: Total flowers
produced by day over
the flowering season.
The coloured region
indicates the time at
which a heatwave was
induced.
THE CENTRE FOR
GLOBAL CHANGE SCIENCE
Methods
• Organism: oilseed Camelina sativa.
• Self-fertilizing.
• Short growing season.
• Established genotype collection.
• Treatments: 5 day 38°C/28°C heatwave
occurring at the early, peak, and late stages
of the flowering season.
• Control: 24°C/18°C.
• Data Collected: open flower counts, branch counts,
and seed pod counts. Seed mass to be collected.
• Sample Size: 42 plants per treatment; n=168.
Control
Peak
Early
Late
• Flower development ceases from the onslaught of a heatwave.
• Following a heatwave, flower production increases across all treatments.
• Climate variability has a disproportionally greater
effect on species compared to increases in mean
climate2.
• Plants can tolerate different types of damage through
various means, including tissue regrowth, increased
flower production, and increased branch initiation.
• Two competing hypotheses/strategies of tolerance:
1. Phenotypic Plasticity3: altering phenotypic traits in
response to damage or stress.
2. Bet Hedging4: diversifying resource investments
temporally to buffer against environmental variation;
maintaining the same overall developmental output.
Figure 1: Increases in mean climate will
bring more frequent hotter weather patterns1.
Research Questions
1. Can plants tolerate heatwave damage?
2. Is tolerance achieved through
phenotypic plasticity or bet hedging?
Camelina sativa
Branching
Figure 3: A diagram showing the order
of branch types on a plant. Clusters of
flowers grow on the tips of branches.
1°
2°
3°
4°
Figure 4: Average aggregate primary (1°),
secondary (2°), tertiary (3°), and quaternary
(4°) branches produced by treatment.
• The number of auxiliary
(2-4°) branches
increases when heat
damage is inflicted.
• Following a heatwave,
flower production
increases across all
treatments.
• Late has the greatest 2-
4° branch production.
Seed Pod Production
Figure 5: Average aggregate number of
seed pods produced per plant by treatment.Figure 6: Average aggregate number of seed
pods produced by treatment and genotype.
Acknowledgements
References1. IPCC. (2007). Climate Change 2007: The Physical Science Basis. Contribution of Working Group I to the Fourth Assessment Report of the
Intergovernmental Panel on Climate Change [Solomon, S., Qin, D., Manning, M., Chen, Z., Marquis, M., Averyt, K.B., Tignor, M., & Miller, H.L
(eds.)]. Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA.
2. Vasseur, D. A., DeLong, J. P., Gilbert, B., Greig, H. S., Harley, C. D., McCann, K. S., ... & O'Connor, M. I. (2014). Increased temperature variation
poses a greater risk to species than climate warming. Proceedings of the Royal Society of London B: Biological Sciences, 281(1779), 20132612
3. Austen, E. J., & Weis, A. E. (2014). Temporal variation in phenotypic gender and expected functional gender within and among individuals in an annual
plant. Annals of botany, 114(1), 167-177.
4. Wadgymar, S.M., Austen, E.J., Cumming, M.N., and Weis, A.E. (2015). Simultaneous pulsed flowering in a temperate legume: causes and
consequences of multimodality in the shape of floral display schedules. Journal of Ecology. 103: 316-327.
5. Seger, J., & Brockmann, H.J. 1987. What is bet-hedging? Pp. 182-211 in P.H. Harvey and L. Partridge, editors. Oxford surveys in evolutionary biology. Oxford University Press. Oxford, UK.
• Treatment and genotype
affect the number of
seed pods produced.
• Similar to flowers, seed
pod production rises
following a heatwave
across all treatments.
• Late has the greatest
seed pod production.
Flowering Season Duration
Figure 7: Flowering season length
by treatment.
Figure 8: Flowering season length
by treatment and genotype.
• Late occurring heatwaves extend the
flowering season significantly.
Conclusions
• Camelina sativa responds plastically to
heatwaves by producing more branches,
flowers, and seed pods.
• The late heatwave produces far more seed
pods than the other treatments.
• Earlier developing seeds could have
aborted from heat damage.
• To determine if the increase in quantity of
seed pods is counterbalanced by the quality
(viability) of seed produced.
Ambient Heatwave
Immense gratitude is directed towards Sarah Hall and Prof. Art Weis for their leadership
and guidance throughout this project. Appreciation is also given to all Weis Lab
volunteers including Nadine, Paula, Noah, Sarah, Kaiwen, Ru, and Melissa. Special
thanks to Sophia Fan for working tirelessly to collect data and care for the plants.
Funding provided by the Centre of Global Change Science Intern Programme 2018.
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