Surfactant-induced enhancement of droplet adhesion in superhydrophobic soybean (Glycine max L.) leaves

This study performed with soybean (Glycine max L.), one of the most important crops for human and animal nutrition, demonstrates that changes in the leaf surface structure can increase the adhesion of applied droplets, even on superhydrophobic leaves, to reduce undesirable soil contamination by roll-off of agrochemical formulations from the plant surfaces. The wettability and morphology of soybean (Glycine max L.) leaf surfaces before and after treatment with six different surfactants (Agnique® SBO10 and five variations of nonionic surfactants) have been investigated. The leaf surface structures show a hierarchical organization, built up by convex epidermal cells (microstructure) and superimposed epicuticular platelet-shaped wax crystals (micro- to nanostructure). Chemical analysis of the epicuticular wax showed that 1-triacontanol (C30H61OH) is the main wax component of the soybean leaf surfaces. A water contact angle (CA) of 162.4° (σ = 3.6°) and tilting angle (TA) of 20.9° (σ = 10.0°) were found. Adherence of pure water droplets on the superhydrophobic leaves is supported by the hydrophilic hairs on the leaves. Agnique® SBO10 and the nonionic surfactant XP ED 75 increased the droplet adhesion and caused an increase of the TA from 20.9° to 85° and 90°, respectively. Scanning electron microscopy showed that surfactants with a hydrophilic–lipophilic balance value below 10 caused a size reduction of the epicuticular wax structures and a change from Cassie–Baxter wetting to an intermediate wetting regime with an increase of droplet adhesion.

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Interaction of surfactants with barley leaf surfaces: time-dependent recovery of contact angles is due to foliar uptake of surfactants

Planta ◽

10.1007/s00425-021-03785-z ◽

2021 ◽

Vol 255 (1) ◽

Author(s):

Johanna Baales ◽

Viktoria V. Zeisler-Diehl ◽

Yaron Malkowsky ◽

Lukas Schreiber

Keyword(s):

Leaf Surface ◽

Pure Water ◽

Contact Angles ◽

Time Dependent ◽

Alcohol Ethoxylate ◽

Leaf Physiology ◽

Surfactant Solutions ◽

Surface Wax ◽

Leaf Surfaces ◽

Barley Leaf

Abstract Main conclusion Time-dependent contact angle measurements of pure water on barley leaf surfaces allow quantifying the kinetics of surfactant diffusion into the leaf. Abstract Barley leaf surfaces were sprayed with three different aqueous concentrations (0.1, 1.0 and 10%) of a monodisperse (tetraethylene glycol monododecyl ether) and a polydisperse alcohol ethoxylate (BrijL4). After 10 min, the surfactant solutions on the leaf surfaces were dry leading to surfactant coverages of 1, 10 and 63 µg cm−2, respectively. The highest surfactant coverage (63 µg cm−2) affected leaf physiology (photosynthesis and water loss) rapidly and irreversibly and leaves were dying within 2–6 h. These effects on leaf physiology did not occur with the lower surfactant coverages (1 and 10 µg cm−2). Directly after spraying of 0.1 and 1.0% surfactant solution and complete drying (10 min), leaf surfaces were fully wettable for pure water and contact angles were 0°. Within 60 min (0.1% surfactant) and 6 h (1.0% surfactant), leaf surfaces were non-wettable again and contact angles of pure water were identical to control leaves. Scanning electron microscopy investigations directly performed after surfactant spraying and drying indicated that leaf surface wax crystallites were partially or fully covered by surfactants. Wax platelets with unaltered microstructure were fully visible again within 2 to 6 h after treatment with 0.1% surfactant solutions. Gas chromatographic analysis showed that surfactant amounts on leaf surfaces continuously disappeared over time. Our results indicate that surfactants, applied at realistic coverages between 1 and 10 µg cm−2 to barley leaf surfaces, leading to total wetting (contact angles of 0°) of leaf surfaces, are rapidly taken up by the leaves. As a consequence, leaf surface non-wettability is fully reappearing. An irreversible damage of the leaf surface fine structure leading to enhanced wetting and increased foliar transpiration seems highly unlikely at low surfactant coverages of 1 µg cm−2.

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Wettability and morphology of the leaf surface in cashew tree from the Amazon, Northern Brazil

Acta Scientiarum Biological Sciences ◽

10.4025/actascibiolsci.v38i2.30806 ◽

2016 ◽

Vol 38 (2) ◽

pp. 215 ◽

Cited By ~ 4

Author(s):

Glenda Quaresma Ramos ◽

Marta Duarte da Fonseca de Albuquerque ◽

José Luiz Pinto Ferreira ◽

Eduardo Adriano Cotta ◽

Henrique Duarte da Fonseca Filho

Keyword(s):

Leaf Surface ◽

Epicuticular Wax ◽

Environmental Scanning ◽

Adaxial Side ◽

Hydrophilic Nature ◽

Ultrastructural Characterization ◽

Static Contact ◽

Leaf Surfaces ◽

Northern Brazil ◽

Cashew Tree

Leaves surfaces, which represent an interface with plants and the environment, have several structures with specific functions. Some foliar properties, including wettability and mechanical containment, are inferred in terms of cellular adaptation and the presence or absence of cuticular wax. Various morphological parameters, ranging from macro- to nano scales, are analyzed and contribute to the study of taxonomy, pharmacognosy, and ecology of plants. The aim of this paper was to analyze the effect and influence of epicuticular wax granules on the hydrophobicity of Anacardium occidentale L. leaf surfaces. Leaf specimens were directly examined with an environmental scanning electron microscope without metal coating. Images revealed epidermis ornament, stomata type, was, and trichomes. Static contact angle between water and the surface was also measured on both sides. On the adaxial side, an angle of 104.09° ± 0.95° was found, suggesting that adaxial surface is hydrophobic. On the abaxial side, the angle was 62.20° ± 1.60°, which indicates a hydrophilic nature, probably because of the greater amount of epicuticular wax on the adaxial leaf surface. The present investigation provided an important contribution to morphological and ultrastructural characterization of leaves of cashew tree, which is a plant of great medicinal and economic importance.

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Artificial Phylloplanes Resembling Physicochemical Characteristics of Selected Fresh Produce and Their Use in Bacteria Attachment/Removal Studies

10.21203/rs.3.rs-971252/v1 ◽

2021 ◽

Author(s):

Sindy Palma-Salgado ◽

Kang-Mo Ku ◽

John A. Juvik ◽

Thanh H. Nguyen ◽

Hao Feng

Keyword(s):

Fresh Produce ◽

Physicochemical Characteristics ◽

Surface Hydrophobicity ◽

Epicuticular Wax ◽

Ionic Surfactant ◽

Human Pathogens ◽

Hydrophilic Lipophilic Balance ◽

Leaf Surfaces ◽

Safety Interventions ◽

Natural Leaf

Abstract The recurrence of food-borne illness outbreaks caused by consumption of fresh produce highlights the importance of developing a good understanding of the bacteria-leaf-surfaces interactions. In this study, we proposed and developed a new method to fabricate artificial phylloplanes that mimic the topographical and epicuticular characteristics of fresh produce, to be used as a platform for the development of food safety interventions for fresh produce. Romaine lettuce and spinach were selected to create phylloplane replicas using a double-cast procedure. The surface hydrophobicity of the artificial phylloplanes made from polydimethylsiloxane (PDMS) was modified by adding a non-ionic surfactant with different hydrophilic-lipophilic balance (HLB) values to match the hydrophobicity of produce leaves. Key epicuticular wax compounds identified from the natural spinach and lettuce leaves were coated on the leaf replica to mimic the chemical composition of natural leaf surfaces. These surrogate surfaces were used to study the attachment Escherichia coli O157:H7 and Listeria innocua. In addition, these surfaces are reusable, and have surface hydrophobicity, surface roughness values and epicuticular wax compositions similar to fresh produce. The artificial phylloplanes of fresh produce can be used as a platform for studying the interactions between human pathogens with produce surfaces and for developing new sanitation strategies.

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Penetration, Translocation, and Metabolism of Acifluorfen in Soybean (Glycine max), Common Ragweed (Ambrosia artemisiifolia), and Common Cocklebur (Xanthium pensylvanicum)

Weed Science ◽

10.1017/s0043174500040029 ◽

1981 ◽

Vol 29 (4) ◽

pp. 474-480 ◽

Cited By ~ 34

Author(s):

Ronald L. Ritter ◽

Harold D. Coble

Keyword(s):

Glycine Max ◽

Leaf Surface ◽

Ambrosia Artemisiifolia ◽

Weed Species ◽

Common Ragweed ◽

Nitrobenzoic Acid ◽

Leaf Surfaces ◽

The Difference ◽

Soybean Plants ◽

Layer Chromatography

Penetration, translocation, and metabolism of acifluorfen {5-[2-chloro-4-(trifluoromethyl)phenoxy]-2-nitrobenzoic acid} in soybean [Glycine max(L.) Merr. ‘Ransom’], common ragweed (Ambrosia artemisiifoliaL.), and common cocklebur (Xanthium pensylvanicumWallr.) were studied. Using liquid scintillation spectrometry and autoradiography, little movement of14C-acifluorfen from the leaf surfaces of the two weed species could be detected in 24 h. After 48 h, less14C was recovered from the leaf surface and more was found within the leaves of the two weed species. Autoradiographs of the weed showed limited acropetal movement of14C from leaves 24 and 48 h after treatment. For soybean, most of the14C still remained on the leaf surface after 48 h. Autoradiographs of soybean plants showed no movement from the treated leaflet. Studies using thin layer chromatography suggested that acifluorfen was metabolized within the plants. Rate of metabolism was inversely related to plant susceptibility (common ragweed and common cocklebur>soybean). The more rapid penetration and translocation, coupled with slower metabolism of acifluorfen by the weed species in comparison to soybean, may account for the difference in susceptibility of the weeds and soybean to acifluorfen.

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Leaf characteristics and surfactants affect primisulfuron droplet spread in three broadleaf weeds

Weed Science ◽

10.1614/ws-05-019r.1 ◽

2006 ◽

Vol 54 (1) ◽

pp. 16-22 ◽

Cited By ~ 16

Author(s):

Debanjan Sanyal ◽

Prasanta C. Bhowmik ◽

Krishna N. Reddy

Keyword(s):

Leaf Surface ◽

Epicuticular Wax ◽

Distilled Water ◽

Weed Species ◽

Spray Droplet ◽

Common Lambsquarters ◽

Leaf Surfaces ◽

Droplet Behavior ◽

Wax Content ◽

Common Purslane

Laboratory studies were conducted to examine the leaf surface, epicuticular wax content, and spray droplet behavior on common lambsquarters, common purslane, and velvetleaf. Adaxial and abaxial leaf surfaces were examined using scanning electron microscopy, and leaf wax was extracted and quantified for all three weed species. The spread of 1-μl droplets of distilled water, primisulfuron solution (without surfactant), primisulfuron solution with a nonionic low foam wetter/spreader adjuvant (0.25% v/v), and with an organosilicone wetting agent (0.1% v/v) was determined on the adaxial leaf surfaces of each of the weed species. Glands and trichomes were present on both the adaxial and abaxial leaf surfaces of velvetleaf. Common purslane had neither glands nor trichomes on either side of the leaf. Common lambsquarters did not have any glands or trichomes, but it had globular bladder hairs on both adaxial and abaxial leaf surfaces. Stomata were present on both adaxial and abaxial leaf surfaces in all three weed species. Common purslane had a much lower number of stomata per unit area of leaf as compared with velvetleaf or common lambsquarters. Common lambsquarters had the highest epicuticular wax content on the leaf surface (274.5 μg cm−2), followed by common purslane (153.4 μg cm−2) and velvetleaf (7.4 μg cm−2). There were no significant variations in the spread of the 1-μl droplet of distilled water and primisulfuron (without adjuvant) among the species. Spread of primisulfuron droplets with surfactant was highest on the leaf surface of velvetleaf that had the lowest wax content. Droplet spread was greatest with organosilicone surfactant followed by the nonionic surfactant.

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Herbicide Deposition on Leaf Surfaces

Weed Science ◽

10.1017/s004317450005654x ◽

1990 ◽

Vol 38 (3) ◽

pp. 280-288 ◽

Cited By ~ 72

Author(s):

F. Dan Hess ◽

Richard H. Falk

Keyword(s):

Cell Walls ◽

Leaf Surface ◽

Epicuticular Wax ◽

Crystalline Form ◽

Spray Solution ◽

Epidermal Surface ◽

Physical Form ◽

Leaf Surfaces ◽

Water Based ◽

Adverse Influence

Leaf surface morphology and physical characteristics of herbicide deposits on leaf surfaces can influence herbicide performance. Leaf surface topography, the degree and type of epicuticular wax formation, and the presence, type, and distribution of trichomes all influence the distribution of a given herbicide formulation sprayed onto a leaf surface. Depressions above anticlinal cell walls accumulate herbicide, thus lessening uniform distribution. As the amount of particulate wax increases, the size of individual spray drop deposits on the leaf decreases, thus resulting in reduced coverage. In many instances the presence of trichomes reduces optimal epidermal coverage by intercepting spray drops before they reach the epidermal surface. Adjuvants reduce the adverse influence of leaf topography, epicuticular wax, and trichomes on herbicide distribution, but their use usually does not yield an even coating over the entire leaf surface. Many herbicides, in pure form, are solids (i.e., crystals) rather than liquids. For most applications, herbicides are dissolved, dispersed, or emulsified in a water-based spray solution. After spraying, water and any solvents evaporate from the leaf surface and herbicides often return to their solid crystalline form. In the few cases that have been studied, less herbicide is absorbed when present on the leaf surface as a solid rather than as a liquid. In many instances, greater effectiveness of a postemergence herbicide may be obtained if attention is given to optimizing the distribution and physical form on sprayed leaf surfaces.

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Influence of light intensity and water stress on leaf surface characteristics of Cynoglossum officinale, Centaurea spp., and Tragopogon spp.

Canadian Journal of Botany ◽

10.1139/b94-169 ◽

1994 ◽

Vol 72 (9) ◽

pp. 1379-1386 ◽

Cited By ~ 12

Author(s):

Mahesh K. Upadhyaya ◽

Nancy H. Furness

Keyword(s):

Light Intensity ◽

Leaf Surface ◽

Surface Characteristics ◽

Moisture Stress ◽

Epicuticular Wax ◽

Centaurea Maculosa ◽

Soil Moisture Stress ◽

Cynoglossum Officinale ◽

Centaurea Diffusa ◽

Leaf Surfaces

Leaf surface characteristics of Cynoglossum officinale, Centaurea diffusa, Centaurea maculosa, Tragopogon dubius, and Tragopogon pratensis, important rangeland weeds of Canada, and effects of light intensity and water stress on these characteristics were studied using scanning electron microscopy. Both adaxial and abaxial leaf surfaces of Cynoglossum officinale were covered with long, uniseriate trichomes with extensive micropapillate sculpturing. The leaf surfaces of Centaurea diffusa and Centaurea maculosa had two types of trichomes: (i) sparsely distributed, multicellular, uniseriate trichomes with ribbon-like chloroform–ether soluble extensions at their tips and (ii) glandular trichomes. Centaurea diffusa and Centaurea maculosa cannot be distinguished on the basis of trichome morphology. No crystalline epicuticular wax was observed on Cynoglossum officinale or Centaurea spp. leaf surfaces. Cynoglossum officinale and Centaurea diffusa uniseriate trichomes became more abundant as light intensity declined. Micropapillate sculpturing on Cynoglossum officinale trichomes disappeared at low light intensities. Ribbon-like extensions at the tips of Centaurea diffusa uniseriate trichomes increased with increase in soil moisture stress. The leaf surfaces of Tragopogon dubius and Tragopogon pratensis lacked trichomes but were covered with tubular epicuticular wax. Tragopogon dubius and Tragopogon pratensis cannot be distinguished on the basis of epicuticular wax morphology. The abundance and size of epicuticular wax crystals on the adaxial leaf surface of Tragopogon pratensis declined with decrease in light intensity and increased with increase in soil moisture stress. Such plasticity of leaf surface morphology may be important in the acclimation of these species to harsh environments. Key words: epicuticular wax, light intensity, moisture stress, scanning electron microscopy, trichomes, weeds.

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Evaluation of Epicuticular Wax Removal from Whole Leaves with Chloroform

Weed Technology ◽

10.1017/s0890037x00037581 ◽

1993 ◽

Vol 7 (3) ◽

pp. 706-716 ◽

Cited By ~ 20

Author(s):

Thomas A. Bewick ◽

Donn G. Shilling ◽

Robert Querns

Keyword(s):

Electron Microscopy ◽

Room Temperature ◽

Leaf Surface ◽

Epicuticular Wax ◽

Fresh Weight ◽

Total Extract ◽

Black Nightshade ◽

Leaf Surfaces ◽

American Black ◽

Scanning Electron

Leaves of torpedograss and American black nightshade were extracted with chloroform at room temperature. A 2-s dip was sufficient to remove most of the epicuticular wax from torpedograss. However, epicuticular hydrocarbon weight represented only 6.4% of the total extract weight and 6.94μg g−1fresh weight of chlorophyll were found in the 2-s extract. This represented 25% of the chlorophyll detected in the 232-h extract. In American black nightshade, epicuticular hydrocarbons continued to be removed from the leaf surface up to 6 h of extraction. Epicuticular hydrocarbons represented 0.6% of total extract weight. In the 6-h extract, 4.02μg g−1fresh weight of chlorophyll were found. This represented 17% of the chlorophyll detected in the 232-h extract. Evaluation of leaf surfaces using scanning electron microscopy indicated that epicuticular wax was being removed from torpedograss leaves up to 1 h. However, there was little visible evidence for wax extraction from the surface of American black nightshade leaves.

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Effects of Organic Solvent on Curing Behavior and Storage Stability for Waterborne Paint Containing Catalyst Encapsulated in Micelles

Coatings ◽

10.3390/coatings11060722 ◽

2021 ◽

Vol 11 (6) ◽

pp. 722

Author(s):

Shuji Yomo

Keyword(s):

Organic Solvent ◽

Organic Solvents ◽

Storage Stability ◽

Dibutyltin Dilaurate ◽

Film Properties ◽

Surfactant Micelles ◽

Catalytic Function ◽

Hydrophilic Lipophilic Balance ◽

Before And After ◽

And Storage

In this study, a 2-pack isocyanate curing waterborne paint (without organic solvents) encapsulating dibutyltin dilaurate (hereinafter, DBTL) in nonionic surfactant micelles with an hydrophilic–lipophilic balance of 13–14 in advance releases DBTL when the micelles are collapsed at 80 °C or higher, whereby the curing progresses rapidly. On the other hand, the viscosity levels of the paint before and after being left at 40 °C for 1 h are almost the same. Organic solvents are mandatory for waterborne paints to provide paint and film properties, but they might collapse the micelles when they are formulated in the paint. In this study, we investigate whether the abovementioned paint containing organic solvents can develop switching functionality in terms of maintaining the storage stability at 40 °C and expressing a catalytic function at 80 °C to progress the curing. As a result, we find that if the solubility of the organic solvent in water at 20 °C is at least 10 g/100 mL and the boiling point is ≤200 °C, both curing and storage stability can be achieved.

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Particle size, leaf pubescence and condition of humidity at leaf surfaces are key factors determining the retention of volcanic ash on crop foliage.

10.5194/egusphere-egu21-7833 ◽

2021 ◽

Author(s):

Noa Ligot ◽

Benoît Pereira ◽

Patrick Bogaert ◽

Guillaume Lobet ◽

Pierre Delmelle

Keyword(s):

Particle Size ◽

Surface Area ◽

Leaf Surface ◽

Volcanic Risk ◽

Chilli Pepper ◽

Leaf Pubescence ◽

Leaf Surfaces ◽

Plant Foliage ◽

Leaf Surface Area ◽

Ash Deposit

Volcanic ashfall negatively affects crops, causing major economic losses and jeopardising the livelihood of farmers in developing countries where agriculture is at volcanic risk. Ash on plant foliage reduces the amount of incident light, thereby limiting photosynthesis and plant yield. An excessive ash load may also result in mechanical plant damages, such as defoliation and breakage of the stem and twigs. Characterising crop vulnerability to ashfall is critical to conduct a comprehensive volcanic risk analysis. This is normally done by describing the relationship between the ash deposit thickness and the corresponding reduction in crop yield, i.e. a fragility function. However, ash depth measured on the ground surface is a crude proxy of ash retention on plant foliage as this metrics neglects other factors, such as ash particle size, leaf pubescence and condition of humidity at leaf surfaces, which are likely to influence the amount of ash that stays on leaves.Here we report the results of greenhouse experiments in which we measured the percentage of leaf surface area covered by ash particles for one hairy leaf plant (tomato, Solanum lycopersicum L.) and one hairless leaf plant (chilli pepper, Capsicum annuum L.) exposed to simulated ashfalls. We tested six particle size ranges (&#8804; 90, 90-125, 125-250, 250-500, 500-1000, 1000-2000 &#181;m) and two conditions of humidity at leaf surfaces, i.e. dry and wet. Each treatment consisted of 15 replicates. The tomato and chilli pepper plants exposed to ash were at the seven- and eight-leaf stage, respectively. An ash load of ~570 g m-2 was applied to each plant using a homemade ashfall simulator. We estimated the leaf surface area covered by ash from pictures taken before and immediately after the simulated ashfall. The ImageJ software was used for image processing and analysis.Our results show that leaf coverage by ash increases with decreasing particle size. Exposure of tomato and chilli pepper to ash &#8804; 90 &#956;m always led to ~90% coverage of the leaf surface area. For coarser particles sizes (i.e. between 125 and 500 &#181;m) and dry condition at leaf surfaces, a significantly higher percentage (on average 29 and 16%) of the leaf surface area was covered by ash in the case of tomato compared to chilli pepper, highlighting the influence of leaf pubescence on ash retention. In addition, for particle sizes between 90 and 500 &#181;m, wetting of the leaf surfaces prior to ashfall enhanced the ash cover by 19 &#177; 5% and 34 &#177; 11% for tomato and chilli pepper, respectively.These findings highlight that ash deposit thickness alone cannot describe the hazard intensity accurately. A thin deposit of fine ash (&#8804; 90 &#181;m) will likely cover the entire leaf surface area, thereby eliciting a disproportionate effect on plant foliage compared to a thicker but coarser deposit. Similarly, for a same ash depth, leaf pubescence and humid conditions at the leaf surfaces will enhance ash retention, thereby increasing the likelihood of damage. Our study will contribute to improve the reliability of crop fragility functions used in volcanic risk assessment.

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