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.

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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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