Dynamic Surface Tension Enhances the Stability of Nanobubbles in Xylem Sap

Autor: Stephen Ingram, Yann Salmon, Anna Lintunen, Teemu Hölttä, Timo Vesala, Hanna Vehkamäki
Jazyk: angličtina
Rok vydání: 2021
Předmět:
Zdroj: Frontiers in Plant Science, Vol 12 (2021)
Druh dokumentu: article
ISSN: 1664-462X
DOI: 10.3389/fpls.2021.732701
Popis: Air seeded nanobubbles have recently been observed within tree sap under negative pressure. They are stabilized by an as yet unidentified process, although some embolize their vessels in extreme circumstances. Current literature suggests that a varying surface tension helps bubbles survive, but few direct measurements of this quantity have been made. Here, we present calculations of dynamic surface tension for two biologically relevant lipids using molecular dynamics simulations. We find that glycolipid monolayers resist expansion proportionally to the rate of expansion. Their surface tension increases with the tension applied, in a similar way to the viscosity of a non-Newtonian fluid. In contrast, a prototypical phospholipid was equally resistant to all applied tensions, suggesting that the fate of a given nanobubble is dependent on its surface composition. By incorporating our results into a Classical Nucleation Theory (CNT) framework, we predict nanobubble stability with respect to embolism. We find that the metastable radius of glycolipid coated nanobubbles is approximately 35 nm, and that embolism is in this case unlikely when the external pressure is less negative than –1.5 MPa.
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