I grew Podocarpus seedlings at elevated temperatures for 16 weeks after which I ran temperature response curves using a Licor 6400 IRGA.
The optimum temperature for photosynthesis remained roughly the same for heat acclimated and none-heat acclimated plants, however, max photosynthesis decreased in the heat acclimated plants. The graph is attached!
Does anyone have an explanation for this?
Dear Kathryn
Thanks for your very helpful response.
Yes, I do believe the plants suffered damage during treatment.
1. Plants were well watered and no heat + drought experiment was done, just Heat and Control.
2. Control - ambient temperatures were between 32 - 36 degrees C
Heat - Between 35 to 40 degrees C
3. Stomatal conductance, Dark Fv/Fm, Chlorophyll content, light sat, light comp, dark respiration rate, max photosynthetic rate are all the same between treatments after the 'acclimation period. Specific Leaf Area (SLA) was higher for heat acclimated plants.
4. Visually the leaves look damaged but this was not seen in the measured chlorophyll content.
My main concern is why do differences between treatments ONLY appear in the temperature response curves? Besides SLA.
An experiment cannot tell you the answer. You will need to ascertain the biochemical changes
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