Did you know that willows account for over 30 percent of all of Canada’s native tree and shrub species? In fact, of the 220 species of woody plants in our natural flora, 76 are willows. Interesting, isn’t it?
A thousand and one willow uses
More and more willow species or cultivars are being used as phytotechnological tools to solve environmental problems. Well adapted to the cold and humid climate of North America, willows serve to stabilize banks, to retain excess fertilizers or pesticides along riparian buffer strips in agricultural areas, to decontaminate polluted soil, or to treat leachate water on landfill sites. Let’s hear it for willows!
Rigorous field work
These plants possess remarkable photosynthetic power. That’s something my research team has just brought to light. We know that willows keep their leaves until very late in the season, at a point when all other tree and shrub species across the landscape are entirely bare and already in winter dress. But are the leaves on these willows functional? We were intrigued. It was in this context that a student doing a research internship, Daphné Gagnon-Fee, joined my laboratory at the Institut de recherche en biologie végétale. Over the fall of 2021, she measured the photosynthesis and gas exchange of three different willow species used for the phytoremediation of contaminated soil in eastern Montréal. Every week, from late August until the last days of November, with mittens on, Daphné, (who was often accompanied by Guylaine, her volunteer mom), took hundreds of measurements on the leaves of these willows. That allowed her to accumulate a great deal of data that were later analyzed with the contribution of two international colleagues, the American Emily Palm and the Italian Werther Guidi Nissim, both of them specialists in photosynthesis.
A super-hard-working plant
What were the results? Surprise! These leaves are completely functional, and perform photosynthesis.
This means that, even very late in the fall, as the days grow shorter and shorter, these willows continue to absorb carbon dioxide, which is chiefly responsible for the greenhouse effect. This also reveals that they’re active and far from being dormant, unlike most other plants at that time of year. This ability to remain functional that long during their growth season would partly explain why willows are so effective in contaminating soil. Willows haven’t finished astonishing us! This discovery was reported in a recent article published in PubMed.1
1 Palm E, Guidi Nissim W, Gagnon-Fee D, Labrecque M. Photosynthetic patterns during autumn in three different Salix cultivars grown on a brownfield site. Photosynth Res. 2022 Nov;154(2):155-167. doi: 10.1007/s11120-022-00958-z. Epub 2022 Sep 14. PMID: 36104474; PMCID: PMC9630210.