Lipids in xylem sap of woody plants across the angiosperm phylogeny

AbstractLipids have been observed attached to lumen-facing surfaces of mature xylem conduits of several plant species, but there has been little research on their functions or effects on water transport, and only one lipidomic study of the xylem apoplast. Therefore, we conducted lipidomic analyses of xylem sap from woody stems of seven plants representing six major angiosperm clades, including basal magnoliids, monocots, and eudicots, to characterize and quantify phospholipids, galactolipids, and sulfolipids in sap using mass spectrometry. Locations of lipids in vessels of Laurus nobilis were imaged using TEM and confocal microscopy. Xylem sap contained the galactolipids di- and mono-galactosyldiacylglycerol (DGDG and MGDG), as well as all common plant phospholipids, but only traces of sulfolipids, with total lipid concentrations in extracted sap ranging from 0.18 to 0.63 nmol / mL across all seven species. Contamination of extracted sap from lipids in cut living cells was found to be negligible. Lipid composition of sap was compared to wood in two species and was largely similar, suggesting that sap lipids, including galactolipids, originate from cell content of living vessels. Seasonal changes in lipid composition of sap were observed for one species. Lipid layers coated all lumen-facing vessel surfaces of Laurus nobilis, and lipids were highly concentrated in inter-vessel pits. The findings suggest that apoplastic, amphiphilic xylem lipids are a universal feature of angiosperms. The findings require a reinterpretation of the cohesion-tension theory of water transport to account for the effects of apoplastic lipids on dynamic surface tension and hydraulic conductance in xylem.

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Dynamic surface tension of xylem sap lipids

Tree Physiology ◽

10.1093/treephys/tpaa006 ◽

2020 ◽

Vol 40 (4) ◽

pp. 433-444 ◽

Cited By ~ 7

Author(s):

Jinlong Yang ◽

Joseph M Michaud ◽

Steven Jansen ◽

H Jochen Schenk ◽

Yi Y Zuo

Keyword(s):

Surface Tension ◽

Surface Area ◽

Xylem Sap ◽

Dynamic Surface Tension ◽

Liquid Interfaces ◽

Surface Tensions ◽

Local Surface ◽

Dynamic Surface ◽

Equilibrium Surface ◽

Pit Membrane

Abstract The surface tension of xylem sap has been traditionally assumed to be close to that of the pure water because decreasing surface tension is thought to increase vulnerability to air seeding and embolism. However, xylem sap contains insoluble lipid-based surfactants, which also coat vessel and pit membrane surfaces, where gas bubbles can enter xylem under negative pressure in the process known as air seeding. Because of the insolubility of amphiphilic lipids, the surface tension influencing air seeding in pit pores is not the equilibrium surface tension of extracted bulk sap but the local surface tension at gas–liquid interfaces, which depends dynamically on the local concentration of lipids per surface area. To estimate the dynamic surface tension in lipid layers that line surfaces in the xylem apoplast, we studied the time-dependent and surface area-regulated surface tensions of apoplastic lipids extracted from xylem sap of four woody angiosperm plants using constrained drop surfactometry. Xylem lipids were found to demonstrate potent surface activity, with surface tensions reaching an equilibrium at ~25 mN m-1 and varying between a minimum of 19 mN m-1 and a maximum of 68 mN m-1 when changing the surface area between 50 and 160% around the equilibrium surface area. It is concluded that xylem lipid films in natural conditions most likely range from nonequilibrium metastable conditions of a supersaturated compression state to an undersaturated expansion state, depending on the local surface areas of gas–liquid interfaces. Together with findings that maximum pore constrictions in angiosperm pit membranes are much smaller than previously assumed, low dynamic surface tension in xylem turns out to be entirely compatible with the cohesion–tension and air-seeding theories, as well as with the existence of lipid-coated nanobubbles in xylem sap, and with the range of vulnerabilities to embolism observed in plants.

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Polar lipids are linked to nanoparticles in xylem sap of temperate angiosperm species

10.1101/2021.10.22.465462 ◽

2021 ◽

Author(s):

Xinyi Guan ◽

H Jochen Schenk ◽

Mary R. Roth ◽

Ruth Welti ◽

Julia Werner ◽

...

Keyword(s):

Lipid Composition ◽

Xylem Sap ◽

Seasonal Difference ◽

Polar Lipids ◽

Contamination Control ◽

Low Concentrations ◽

Angiosperm Species ◽

Liquid And Solid Phases ◽

Control Samples ◽

Xylem Conduits

Xylem sap of angiosperm species has been found to include low concentrations of polar lipids and nanoparticles, including surfactant-coated nanobubbles. Although the nanoparticles have been suggested to consist of polar lipids, no attempt has been made to determine if nanoparticle and lipid concentrations are related. Here, we examined concentrations of nanoparticles and lipids in xylem sap and contamination control samples of six temperate angiosperm species with a NanoSight device and based on mass spectrometry. We found (1) that the concentration of nanoparticles and lipids were both diluted when an increasing amount of sap was extracted, (2) that their concentrations were significantly correlated in three species, (3) that their concentrations were affected by vessel anatomy, and (4) that concentrations of nanoparticles and lipids were very low in contamination-control samples. Moreover, there was little seasonal difference, no freezing-thawing effect on nanoparticles, and little seasonal variation in lipid composition. These findings indicate that lipids and nanoparticles are related to each other, and largely do not pass interconduit pit membranes. Further research is needed to examine the formation and stability of nanoparticles in xylem sap in relation to lipid composition, and the complicated interactions among the gas, liquid, and solid phases in xylem conduits.

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Dynamic Surface Tension Enhances the Stability of Nanobubbles in Xylem Sap

Frontiers in Plant Science ◽

10.3389/fpls.2021.732701 ◽

2021 ◽

Vol 12 ◽

Author(s):

Stephen Ingram ◽

Yann Salmon ◽

Anna Lintunen ◽

Teemu Hölttä ◽

Timo Vesala ◽

...

Keyword(s):

Surface Tension ◽

Surface Composition ◽

Xylem Sap ◽

Dynamic Surface Tension ◽

External Pressure ◽

Nucleation Theory ◽

Classical Nucleation Theory ◽

Dynamic Surface ◽

Biologically Relevant ◽

Dynamics Simulations

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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Dynamic surface tension of xylem sap at the air-water interface

10.5194/egusphere-egu21-10851 ◽

2021 ◽

Author(s):

Reddy Prasanna Duggireddy ◽

Eran Raveh ◽

Gilboa Arye

Keyword(s):

Surface Tension ◽

Surface Activity ◽

Pure Water ◽

Xylem Sap ◽

Dynamic Surface Tension ◽

Bulk Solution ◽

Diffusion Control ◽

Dynamic Surface ◽

Equilibrium Surface Tension ◽

Air Interface

The surface tension (ST) of xylem sap at the water-air interface is a crucial phenomenon, influencing many physiological events such as air seeding and embolism, by which xylem vessels become air-filled and cease to function. Refilling of embolized, may relies on sap&#8217;s surface activity at the interface. It is commonly assumed that the ST of xylem sap is equal to the ST of pure water (72 mN/m). However, xylem sap is a complex solution and consists of surface-active molecules that may adsorb and accumulate at the water-air interface and thereby reduce the ST of water as a function of their aqueous concentration. However, when a new water-air interface is formed, equilibrium ST is not reached instantaneously. Specifically, amphiphilic molecules are kinetically adsorbed and undergo orientation at the interface following diffusion from the bulk solution. Dynamic ST of xylem sap and liquid-solid interactions, describing the surface phenomena of the xylem of vascular plants is currently not fully understood. This is mainly due to a lack of quantitative knowledge on the rate and extent of dynamic and equilibrium ST of sap. In this regard, the main objective of this study is to quantify the dynamic and equilibrium ST of xylem sap as a function of their aqueous concentration. We extracted xylem sap from lemon trees and measured ST as a function of time using the pendant drop technique. The dynamic ST data were analyzed using empirical and diffusion-control mathematical models which adequately described the exponential-like decay of the ST as a function of time. The results showed reduced ST of water in the xylem sap, indicating significant surface activity, reaching equilibrium ST values as low as 42 mN/m. The rate of ST decay was higher in high sap concentration and reduced in diluted one. The results of dynamic and equilibrium ST and the corresponding model will be presented and their implications for xylem hydraulic functioning will be discussed.&#160;Keywords: Dynamic surface tension, Equilibrium surface tension, Diffusion, Xylem sap.&#160;

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The role of dynamic surface tension in air assist atomization

International Journal of Multiphase Flow ◽

10.1016/s0301-9322(97)88506-0 ◽

1996 ◽

Vol 22 ◽

pp. 139

Author(s):

U Shavit

Keyword(s):

Surface Tension ◽

Dynamic Surface Tension ◽

Dynamic Surface

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A pH-Responsive Foam Formulated with PAA/Gemini 12-2-12 Complexes

Colloids and Interfaces ◽

10.3390/colloids5030037 ◽

2021 ◽

Vol 5 (3) ◽

pp. 37

Author(s):

Hernán Martinelli ◽

Claudia Domínguez ◽

Marcos Fernández Leyes ◽

Sergio Moya ◽

Hernán Ritacco

Keyword(s):

Surface Tension ◽

Dynamic Surface Tension ◽

Foam Formation ◽

Ph Responsive ◽

Dynamic Surface ◽

X Ray ◽

Equilibrium Surface Tension ◽

Potential Applications ◽

The Stability ◽

Air Interfaces

In the search for responsive complexes with potential applications in the formulation of smart dispersed systems such as foams, we hypothesized that a pH-responsive system could be formulated with polyacrylic acid (PAA) mixed with a cationic surfactant, Gemini 12-2-12 (G12). We studied PAA-G12 complexes at liquid–air interfaces by equilibrium and dynamic surface tension, surface rheology, and X-ray reflectometry (XRR). We found that complexes adsorb at the interfaces synergistically, lowering the equilibrium surface tension at surfactant concentrations well below the critical micelle concentration (cmc) of the surfactant. We studied the stability of foams formulated with the complexes as a function of pH. The foams respond reversibly to pH changes: at pH 3.5, they are very stable; at pH > 6, the complexes do not form foams at all. The data presented here demonstrate that foam formation and its pH responsiveness are due to interfacial dynamics.

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Laser-based dynamic surface tension detection for liquid chromatography by probing a repeating drop radius

Journal of Chromatography A ◽

10.1016/0021-9673(94)00538-k ◽

1995 ◽

Vol 691 (1-2) ◽

pp. 195-204 ◽

Cited By ~ 9

Author(s):

Lawrence R. Lima ◽

Robert E. Synovec

Keyword(s):

Surface Tension ◽

Liquid Chromatography ◽

Dynamic Surface Tension ◽

Dynamic Surface ◽

Drop Radius

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Pool Boiling Heat Transfer in Aqueous Solutions of an Anionic Surfactant

Journal of Heat Transfer ◽

10.1115/1.1316785 ◽

2000 ◽

Vol 122 (4) ◽

pp. 708-715 ◽

Cited By ~ 91

Author(s):

V. M. Wasekar ◽

R. M. Manglik

Keyword(s):

Anionic Surfactant ◽

Pure Water ◽

Pool Boiling ◽

Sodium Dodecyl ◽

Dynamic Surface Tension ◽

Nucleate Boiling ◽

Optimum Level ◽

Lauryl Sulfate ◽

Dynamic Surface ◽

Influence Of Temperature On

Saturated nucleate pool boiling of aqueous surfactant solutions on a horizontal cylindrical heater has been experimentally investigated. Sodium dodecyl or lauryl sulfate (SDS or SLS), an anionic surfactant, is employed. Boiling performance, relative to that for pure water, is found to be enhanced significantly by the presence of SDS, with an early onset of nucleate boiling. An optimum level of enhancement is observed in solutions at or near critical micelle concentration of the surfactant; the enhancement, however, decreases considerably in higher concentration solutions. The dynamic surface tension measurements indicate a substantial influence of temperature on the overall adsorption isotherm. The diffusion kinetics of surfactant molecules and micelles is, therefore, expected to be quite different at boiling temperature than at room temperature. This greatly modifies the boiling mechanism that is generally characterized by the formation of smaller-size bubbles with increased departure frequencies, and a decreased tendency to coalesce which causes considerable foaming. [S0022-1481(00)00704-0]

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An axisymmetric model for the analysis of dynamic surface tension

RSC Advances ◽

10.1039/c4ra10845k ◽

2015 ◽

Vol 5 (11) ◽

pp. 7921-7931 ◽

Cited By ~ 2

Author(s):

S. I. Arias ◽

J. R. Fernández ◽

L. García-Rio ◽

J. C. Mejuto ◽

M. C. Muñiz ◽

...

Keyword(s):

Surface Tension ◽

Diffusion Length ◽

Dynamic Surface Tension ◽

Ionic Surfactants ◽

Adsorption Behaviour ◽

Dynamic Surface ◽

Axisymmetric Model

An axisymmetric model accounts for dynamic surface tension of non-ionic surfactants under consideration of diffusive adsorption behaviour with a finite diffusion length.

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