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Mardi 3 Novembre 2015 / IUSTI

publié le

Séminaire exceptionnel IUSTI

Physics inspired by vegetal physiology : bubbles nucleation in trees and locomotion of Equisetum spore

Orateur : Alexandre Ponomarenko
Laboratoire LIPHY, Grenoble

Résumé : I will present two responses of plants to the variations of relative humidity in surrounding air :

One is the response of a tree to a drought. It is known that under drought conditions, when air gets dry, the pressure in ascending sap decreases. It decreases so much that the pressure drops below vapour pressure and may even be negative. In those conditions sap is in a metastable state and may form bubbles of water vapour. Those bubbles form an embolism in the hydraulic pathway of trees, decreasing or even stopping sap ow and possibly causing trees’ death. At the same time, during drought, sounds are heard in trees. To answer the question how acoustics and optics are linked together ? I will present a device that enable to observe optically and acoustically a tree sample in drought conditions.

The second is the locomotion of Equisetum spores caused by oscillations of air relative humidity between dry and wet. The spores of this plant have a spherical body of 50μm size and four ’arms’ called elaters that have a hygroscopic response : they open and close with air humidity variations. We will see how this hygroscopic response participates to the locomotion of Equisetum spores.

Date et lieu : le Mardi 3 Novembre 2015 à 11h00, salle 250 IUSTI