Create your own conference schedule! Click here for full instructions

The Virtual Conference is located at

Abstract Detail


Velasco, Vera [1], Noordermeer, Devin [2], Sen, Tomoyuki [2], Ensminger, Ingo [2].

Impact of combined heat and drought on water content, photosynthesis, and chlorophyll fluorescence in interior and coastal Douglas-fir provenances.

Natural populations of Douglas-fir (Pseudotsuga menziesii) are found in a wide range of environmental conditions and have high intraspecific variation in many traits including those responsive to climate-related stressors. As such, it is predicted that some Douglas-fir provenances may successfully adapt to climate change. Here, we investigated how Douglas-fir provenances locally adapted to wet, dry, hot and cool environments will respond to simulation of future 2080 climate.    We hypothesized that Douglas-fir that originated from hot and dry environment will have water-related and photosynthesis traits that can adjust to combined drought and heat stress (heatwave). We exposed Douglas-fir from interior variety (Little Elk and Meldrum Creek provenances) and coastal variety (Pemberton and Tsowwin River provenances) to four weeks of intense drought, heat, and heatwave simulations in greenhouses.    We determined plant canopy temperature (Tc) using thermal imaging, and water plant status through quantification of relative water content (RWC) and pre-dawn water potential (ψw). We also assessed photosynthesis and photoprotective capacity through measurement of net photosynthesis (Anet), stomatal conductance (gs), proportion of light used for photochemistry (φPSII) and carotenoid content.   Douglas-fir exposure to four weeks of intense heat with 33 °C/44 °C day/night temperatures resulted in heightened Tc, and decreased RWC, ψw, gs, Anet and φPSII.   We also observed increased concentrations of carotenoid pigments namely violaxanthin, antheraxanthin, and zeaxanthin.   Four weeks of drought resulted in much lower RWC, ψw, gs, Anet, and φPSII in all Douglas-fir provenance while the concentration of carotenoids increased to the same level as drought.   We observed drastic changes in Douglas-fir physiology due to the combination of drought and heat.    Heatwave-treated Douglas-fir plants had high Tc at levels higher than the environment, very low plant water status as shown by decreased RWC and ψw, negligible photosynthesis, tightly closed stomates, decreased φPSII, and high concentration of carotenoids. Taken together, we observed that Douglas-fir was able to acclimate to either drought or heat through decreased carbon uptake caused by stomatal limitations that serve to conserve water.   However, a combination of drought and heat was fatal to all provenances and showed not only decreased photosynthesis and upregulation of photoprotective processes but signs of wilting, senescence, and mortality.

Log in to add this item to your schedule

Related Links:
CoAdapTree Project

1 - University Of Toronto, OVPR, 3359 Mississauga Rd, Mississauga, ON, L5L1C7, Canada
2 - University of Toronto, 3359 Mississauga Rd, Mississauga, ON, L5L1C6, Canada

heat stress
Chlorophyll a fluorescence
abiotic stress
FLIR thermal Imaging.

Presentation Type: Oral Paper
Session: PHYS, Physiology
Location: /
Date: Wednesday, July 21st, 2021
Time: 1:00 PM(EDT)
Number: PHYS009
Abstract ID:1020
Candidate for Awards:None

Copyright © 2000-2021, Botanical Society of America. All rights reserved