Resistance of plants to extreme drought
with Philippe Marmottant, Hervé Cochard, Éric Badel, Olivier Vincent, Diane Bienaimé, Marco Vitali, Missy Holbrook, Fulton Rockwell, Uri Hochberg Jessica Gersony and Shmuel Rubinstein
Huge amounts of sap flow in plants from the roots to the leaves, it can be 100L for a 15m height oak for example. The driving force of this flow is evaporation of sap at the leaves that decrease sap pressure in the plant. During a drought, evaporation increases and sap pressure decreases more than usual, sap may change from liquid phase to gas phase and a gas embolism start to propagate in the tree. We are interested in explaining how and when the gas bubbles appear and by which mechanisms they propagates in the tree. Our approach is to make new observations of these mechanisms directly in plants and to build biomimetic systems.
Resistance of plants to extreme cold events
with Thierry Améglio, Katline Charra-Vaskou and Guillaume Charrier
Plants are also known to fail under cold events, and different species will die at different cooling rates or cold temperatures, with records at -80°C. While the big picture would be to correlate the anatomy of each plants and the freezing conditions at which they die, we first focus on the mechanisms that kill the plant: breaking of the living cells that freeze or drying of cells caused by nearby frozen water: during cold events, tree can die because of freezing or drying!
Breaking of plants during wind storms: wind lodging
with Christophe Clanet, David Quéré, Éline Dehandschoewercker and Emmanuel Virot
We have compared maps of wind during storms and maps of trees damage right after storms. It shows that there is a critical wind speed at which a majority of trees break. We question the physical origin of this observation both experimentally and theoretically. By combining Hooke’s law, Griffith’s criterion, and tree allometry, we show that the critical wind speed indeed hardly depends on the height, diameter, and elastic properties of trees.
Popping of popcorn seeds
with Emmanuel Virot
We have made experiments on popcorn bursting mainly with an educational goal. It is a great topic to share with people and students and its study needs to use different fields: thermodynamics, biomechanics and fracture. We have explained the temperature at which popcorn explodes, its jump and the pop sound it makes when exploding.
Locomotion of Equisetum spores
with Philippe Marmottant and Diane Bienaimé
Equisetum is a plant living in wet areas. Its spores have a spherical body with four elaters that are hygroscopic elongated cells which change shape with change of air relative humidity. We studied the role of those elaters involved in the locomotion of the spores of this plant and showed that when a dry wind is blowing the spores can jump and get carried on long distances by the wind.