Poplar trees are known to produce a chemical called isoprene that plays a complex, and not fully understood, role in the chemical process of photosynthesis. Understanding why plants produce isoprene and under what conditions will help scientists make more accurate predictions about poplars’ photosynthetic capabilities in future climates.
What benefit could isoprene provide a plant? The literature suggests its production could help plants tolerate heat stress. We studied two genetic lines of trees in a common garden of Populus, one line with the gene for producing isoprene and a second line without that gene. We subjected some trees of each line to low water conditions to investigate if isoprene played a role in allowing plants to cope with water stress. We then compared the ability of these 4 treatment groups of poplars to photosynthesize over a range of temperatures.
Poplars with and without isoprene showed similar rates of photosynthesis over the range of temperatures measured. Poplars subjected to low water conditions and poplars with normal water conditions also recorded similar rates of photosynthesis. This suggests that isoprene does not offer a photosynthetic benefit, and also that the low water conditions may not have triggered a water stressed state in the poplars. However, the poplars’ rate of photosynthesis differed between morning and afternoon, suggesting that time of day could play a role in photosynthesis. Future work is needed to understand how the influence of time of day on photosynthesis may overshadow any differences due to isoprene production.