Illustrating 3 unexpected lessons we learned whilst studying diurnal patterns of light transmittance of leaves
Author: Santa Neimane (University of Helsinki & University of Latvia)
Location: 02(b) Alps, France
Before we go ahead with the countdown of the new insights that we learned, but didn’t expect, first let me introduce you to the research project. We wanted to determine which part of the light spectrum is used as a cue for plants to alter UV transmittance of leaf epidermis, which in turn may act as a protection mechanism under excessive irradiance. Hence the name for the project: Sun-Signal. Additionally, led by plant physiologists Beatriz Fernandez-Marin and Jose Ignacio Garcia Plazaola, we looked at plant acclimation across a snow gradient which is particularly important considering climate change induced differences in snow cover. We set out to complete this study at the Station Alpine Joseph Fourier in the French Alps at an altitude of 2100 m which provided us with a quite unique environment, not only climatically! We had the opportunity to examine both the plants surrounding the research station and access the Lautaret Alpine Garden right next to it. If you wish to see the results from this project, keep track of @CanopySEE on twitter and visit the CanSEE Group Website.
The first conclusion from our time in the Alps – sometimes it can be fun to stumble around in the midnight with a UV flashlight. Encouraged by Pedro J. Aphalo, who also took photos of the flowers showing their reflectance in UV, we headed out to the botanical garden in the middle of the night and looked at the UV reflectance of everything we could get hold of (as most of the plants were not flowering yet, this was difficult enough). To our surprise, we found one of the most interesting sights on a rock, in UV light reflectance hid the typically invisible world.
Fig 1. The left-hand photo shows lichens on the rock in the research station under visible light conditions, whilst for the picture on the right the light source is a UV flashlight. These photos and more taken by P.J. Aphalo can be found here on his blog.
Second observation. Cover images for albums can be made by taking a bunch of people, letting them do measurements throughout the day for two weeks, preferably with the smallest curliest leaves possible and under the widest set of weather conditions. And then encouraging them to go for a hike up a mountain.
Fig 2. The Album Cover shot. Photo taken by P.J. Aphalo of all other field work group members on the last day of the project – after taking A LOT of measurements, hence those deep stares into the distance!
The last and probably the most important lesson (at least until the results of the study have been analyzed) is – wear sunscreen! In alpine environments, the amount of UV is higher and, also, as we measured, almost all of the light from the snow is reflected. Even the most educated ones, may sometimes underestimate the damaging effects of UV light and end up with irritated skin and strangely shaped tattoos from their hats and t-shirts.
Fig 3. The upper photo shows the main study area and the team members. The lower photos are of some of the plant species included in the study (Gentiana acaulis & Primula involucrata) and team leaders Matthew Robson and Pedro J. Aphalo taking snow reflectance measurements with a spectrometer.
We enjoyed our visit to the Alps and luckily enough the weather was better than expected for the time-of-year, so we had plenty of sunny days as well (as you can guess, that can be very important for photobiologists). By the end of this project we had data about the light spectral quality at the field site, changes in plant pigments and fluorescence at different points in the day, leaf optical properties of multiple alpine plant species, and even more will be found out from later analysis of the frozen samples. We wish to express our gratitude to everyone who made this project possible.
About the author
Santa was a master degree student at the University of Latvia who spent 2017 with Canopy spectral ecology and ecophysiology (CanSEE) research group at the University of Helsinki.
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