Research on the changes in wettability of rice (Oryza sativa.) leaf surfaces at different development stages using the OWRK method

Harnessing Multiscale Physiochemical Interactions on Nanobiointerface for Enhanced Stress Resilience in Rice

Nanoagrochemicals present promising solutions for augmenting conventional agriculture, while insufficient utilization of nanobiointerfacial interactions hinders their field application. This work investigates the multiscale physiochemical interactions between nanoagrochemicals and rice (Oryza sativa L.) leaves and devises a strategy for elevating targeting efficiency of nanoagrochemicals and stress resilience of rice. We identified multiple deposition behaviors of nanoagrochemicals on hierarchically structured leaves and demonstrated the crucial role of leaf microarchitectures. A transition from the Cassie-Baxter to the Wenzel state significantly changed the deposition behavior from superlattice assembly, ring-shaped aggregation to uniform monolayer deposition. By fine-tuning the formulation properties, we achieved a 415.9-fold surge in retention efficiency, and enhanced the sustainability of nanoagrochemicals by minimizing loss during long-term application. This biointerface design significantly relieved the growth inhibition of Cd(II) pollutant on rice plants with a 95.2% increase in biomass after foliar application of SiO2 nanoagrochemicals. Our research elucidates the intricate interplay between leaf structural attributes, nanobiointerface design, and biological responses of plants, fostering field application of nanoagrochemicals.

The effect of Aceria litchii (Keifer) infestation on the surface properties of litchi leaf hosts

BACKGROUND

The wettability of target crop surfaces affects pesticide wetting and deposition. The structure and properties of the leaf surface of litchi leaves undergo severe changes after infestation by Aceria litchii (Keifer). The objective of this study was to systematically investigate the surface texture and wettability of litchi leaves infested.

RESULTS

Firstly, the investigation focused on the surface structure and physicochemical properties of litchi leaves infested with Aceria litchii. Subsequently, different levels of Contact Angle (CA) were measured individually on the infested litchi leaves. Lastly, Surface Free Energy (SFE) and its polar and dispersive components were calculated using the Owens-Wendt-Rabel-Kaelble (OWRK) method. The outcomes revealed distinctive 3D surface structures of the erineum at various stages of mycorrhizal growth. At stage NO. 1, the height of the fungus displayed a peaked appearance, with the skewness value indicating a surface characterized by more crests. In contrast, at stages NO. 2 and NO. 3, the surface appeared relatively flat. Furthermore, post-infestation of litchi leaves, the CA of droplets on the abaxial surface of diseased leaves exhibited an increase, while the SFE value on the abaxial surface of leaves decreased significantly, in contrast to the abaxial surface of healthy leaves.

CONCLUSION

The infestation behavior of Aceria litchii changed the surface structure and chemistry of litchi leaves, which directly affected the CA value of foliar liquids and the SFE value of leaves, changing the surface wettability of litchi leaves from hydrophobic to superhydrophobic. This study provides useful information for improving the wetting and deposition behavior of liquid droplets on the surface of infested leaves. © 2024 Society of Chemical Industry.

Performance matching of common pesticides in banana plantations on the surface of banana leaves at different growth stages

BACKGROUND

The effective deposition of pesticide droplets on a target leaf surface is critical for decreasing pesticide application rates. The wettability between the target leaf surface and the pesticide spray liquid should be investigated in depth, with the aim of enhancing the adhesion of pesticide solutions. The wetting and deposition behavior of pesticides on target leaves depends on the properties of the liquid and the physical and chemical properties of the leaves. The physical and chemical properties of leaves vary with growth stage. This study aims to investigate the wetting behavior of banana leaf surfaces at different stages.

RESULTS

The microstructures and chemical compositions of banana leaf surfaces at different stages were studied using modern methods. The surface structure of banana leaves exhibited a wide variety of characteristics at different growth stages, and the chemical composition changed marginally. The surface free energy (SFE) and polar and non-polar components of banana leaves at different growth stages were measured by examining the contact angles (CA) of different test solutions on the surface of banana leaves. Previous research has suggested that changes in the CA and SFE correlate with changes in leaf surface wettability. In general, the new upper leaves of banana trees are composed of polar components and exhibit hydrophobicity. Non-polar components become dominant as the leaf grows. The back surface of banana leaves was non-polar at all growth stages, with a trend that was opposite to that of the front surface. The critical surface tension of the banana leaf surface at different growth stages ranged from 7.83 to 24.22 mN m-1 , thus falling into the category of a low-energy surface.

CONCLUSION

The surface roughness and chemical characteristics of banana leaves affected the wettability of the leaf surface. Differences in the free energy and the polar and non-polar components of the leaf surface at were seen at different growth stages. This study provides a favorable reference for the rational control of pesticide spraying parameters and the enhancement of wetting and adhesion of the solution on banana leaf surfaces. © 2023 Society of Chemical Industry.

Sustained Agricultural Spraying: From Leaf Wettability to Dynamic Droplet Impact Behavior

Crop production and quality safety system have the potential to nurture human health and improve environmental sustainability. Providing a growing global population with sufficient and healthy food is an immediate challenge. However, this system largely depends on the spraying of agrochemicals. Crop leaves are covered with different microstructures, exhibiting distinct hydrophilic, hydrophobic, or even superhydrophobic wetting characteristics, thus leading to various deposition difficulties of sprayed droplets. Here, the relationship between wettability and surface microstructure in different crop leaves from biological and interfacial structural perspectives is systematically demonstrated. A relational model is proposed in which complex microstructures lead to stronger leaf hydrophobicity. And adding surfactant with a faster dynamically migrating velocity and reducing droplet size can improve agrochemical precise deposition. These contribute toward highly accurate and efficient targeted applications with fewer agrochemicals use and promote sustainable models of eco-friendly agriculture systems.

Study of Surface Wettability of Mineral Rock Particles by an Improved Washburn Method

The surface wettability of rocks in underground reservoirs affects the distribution of fluids in the reservoir, so the wettability of reservoir minerals is a key factor for crude oil recovery from reservoirs. In this paper, the wettability of quartz sand with different particle sizes in different polar solvents was determined by Washburn's capillary rise method, and the C·cos θ values were calculated first. Next, the experimentally obtained macroscopic contact angle of water on the quartz surface of 15.0° was substituted into C·cos θ to obtain a linear equation between the particle size of quartz sand and the capillary constant C. The particle sizes of oil sand and mineral powder were then substituted into the equation to obtain their capillary constants C. Then, based on the Owens-Wendt-Rabel-Kaelbe (OWRK) equation and the obtained contact angles of solvent on quartz sand, oil sand, and mineral powder, the surface free energy of quartz sand with different particle sizes is calculated as 76.09, 76.65, and 76.42 mN/m, respectively, which are close to the literature results. In addition, the surface free energy of oil sand with different particle sizes was 23.22, 23.45, and 23.63 mN/m, and the results indicated that the polarity of oil sand was low. Meanwhile, the surface free energies of kaolinite, illite, feldspar, and montmorillonite were 61.59, 32.85, 35.87, and 25.91 mN/m, respectively. By the improved Washburn method in this paper, the wettability of different solvents on the surface of reservoir rocks was investigated, and the surface free energy of specific solid particles was calculated, which is important for studying the extraction of crude oil from subsurface reservoir rocks.

Uptake, Translocation, and Terminal Residue of Chlorantraniliprole and Difenoconazole in Rice: Effect of the Mixed-Application with Adjuvant

Plant oil adjuvants are widely used to improve the utilization rate of pesticides. In this study, the uptake, translocation, and terminal residue of chlorantraniliprole and difenoconazole spraying with plant oil adjuvant in rice (Oryza sativa L.) were evaluated. After being mixed with the tank-mixed plant oil adjuvant, the cuticular wax of rice leaf was destroyed, which decreased the hydrophobicity of the rice leaf and facilitated the wetting, spreading, and penetration of pesticides onto the rice leaf. Additionally, the adjuvant promoted the translocation of difenoconazole from leaves to stems, but had little effect on the translocation of difenoconazole from leaves to roots, while inhibiting chlorantraniliprole translocation. Although adjuvant increased the initial deposition of chlorantraniliprole and difenoconazole on rice, the terminal residue was not significantly affected. The findings can promote the safe use of chlorantraniliprole and difenoconazole in rice production, especially when used with plant oil adjuvants. In the future, studies on more rice cultivars will be necessary to determine the generality of the conclusions.

Improved Method to Characterize Leaf Surfaces, Guide Adjuvant Selection, and Improve Glyphosate Efficacy

Glyphosate, one of the most widely used herbicides, plays an important role in controlling weeds and ensuring crop production. While using glyphosate, adjuvants are commonly added to improve its deposition on weeds and control efficacy. However, changes in weed leaf surface characteristics may reduce glyphosate penetration and contribute to evolved glyphosate resistance. Therefore, it is significant to introduce an improved method for regularizing leaf surface characterization and guide adjuvant selection to improve glyphosate efficacy. In this work, surface characteristics of typical weed leaves have been systematically investigated by 3D surface analysis and scanning electron microscopy, finally quantified by apparent surface free energy (ASFE) due to its comprehensive and quantitative evaluation of leaf surfaces. Moreover, the relationship between the weed leaf surface characteristics and the retention of glyphosate on weeds was established, further related to the control efficacy against weeds. To maximize the utilization rate of glyphosate, the types and concentrations of adjuvants should be regulated according to the ASFE of weeds. Our findings not only regularize the surface properties of weed leaves but also reveal their influencing mechanism on the deposition and biological activity of glyphosate, which provide effective guidance for the use of glyphosate.

Modulated Laser Cladding of Implant-Type Coatings by Bovine-Bone-Derived Hydroxyapatite Powder Injection on Ti6Al4V Substrates-Part I: Fabrication and Physico-Chemical Characterization

The surface physico-chemistry of metallic implants governs their successful long-term functionality for orthopedic and dentistry applications. Here, we investigated the feasibility of harmoniously combining two of the star materials currently employed in bone treatment/restoration, namely, calcium-phosphate-based bioceramics (in the form of coatings that have the capacity to enhance osseointegration) and titanium alloys (used as bulk implant materials due to their mechanical performance and lack of systemic toxicity). For the first time, bovine-bone-derived hydroxyapatite (BHA) was layered on top of Ti6Al4V substrates using powder injection laser cladding technology, and then subjected, in this first stage of the research, to an array of physical-chemical analyses. The laser processing set-up involved the conjoined modulation of the BHA-to-Ti ratio (100 wt.% and 50 wt.%) and beam power range (500-1000 W). As such, on each metallic substrate, several overlapped strips were produced and the external surface of the cladded coatings was further investigated. The morphological and compositional (SEM/EDS) evaluations exposed fully covered metallic surfaces with ceramic-based materials, without any fragmentation and with a strong metallurgical bond. The structural (XRD, micro-Raman) analyses showed the formation of calcium titanate as the main phase up to maximum 800 W, accompanied by partial BHA decomposition and the consequential advent of tetracalcium phosphate (markedly above 600 W), independent of the BHA ratio. In addition, the hydrophilic behavior of the coatings was outlined, being linked to the varied surface textures and phase dynamism that emerged due to laser power increment for both of the employed BHA ratios. Hence, this research delineates a series of optimal laser cladding technological parameters for the adequate deposition of bioceramic layers with customized functionality.

Influence of Ceramic Particles Size and Ratio on Surface-Volume Features of the Naturally Derived HA-Reinforced Filaments for Biomedical Applications

The intersection of the bone tissue reconstruction and additive manufacturing fields promoted the advancement to a prerequisite and new feedstock resource for high-performance bone-like-scaffolds manufacturing. In this paper, the proposed strategy was directed toward the use of bovine-bone-derived hydroxyapatite (HA) for surface properties enhancement and mechanical features reinforcement of the poly(lactic acid) matrix for composite filaments extrusion. The involvement of completely naturally derived materials in the technological process was based on factors such as sustainability, low cost, and a facile and green synthesis route. After the HA isolation and extraction from bovine bones by thermal processing, milling, and sorting, two dependent parameters—the HA particles size (<40 μm, <100 μm, and >125 μm) and ratio (0−50% with increments of 10%)—were simultaneously modulated for the first time during the incorporation into the polymeric matrix. The resulting melt mixtures were divided for cast pellets and extruded filaments development. Based on the obtained samples, the study was further designed to examine several key features by complementary surface−volume characterization techniques. Hence, the scanning electron microscopy and micro-CT results for all specimens revealed a uniform and homogenous dispersion of HA particles and an adequate adhesion at the ceramic/polymer interface, without outline pores, sustained by the shape and surface features of the synthesized ceramic particles. Moreover, an enhanced wettability (contact angle in the ~70−21° range) and gradual mechanical takeover were indicated once the HA ratio increased, independent of the particles size, which confirmed the benefits and feasibility of evenly blending the natural ceramic/polymeric components. The results correlation led to the selection of optimal technological parameters for the synthesis of adequate composite filaments destined for future additive manufacturing and biomedical applications.

Effects of temperature and humidity on the contact angle of pesticide droplets on rice leaf surfaces

The effects of external factors such as temperature, humidity, pesticide formulation, and pesticide concentration on the contact angle of pesticide droplets on rice leaf surfaces were analyzed. The experiments showed that there were significant differences in the contact angles of droplets on the leaf surfaces under different temperatures and humidity. As the ambient temperature increased, the contact angle first decreased and then increased, reaching a minimum value at 25°C. With a gradual increase in humidity, the contact angle significantly increased and reached a maximum at 100% humidity. Finally, it was concluded that both the formulation and concentration of the pesticide had a significant effect on the contact angle of droplets on rice leaf surfaces. The experiments also illustrated that the effects of the pesticide formulation and concentration on the contact angle were more significant than those of temperature and humidity.

Effect of Adjuvants on the Wetting Behaviors of Bifenthrin Droplets on Tea Leaves

The hydrophobic epicuticle wax on fresh leaves of tea tree (Camellia sinensis (L.) 0. Kuntze) leads to the loss of pesticide droplets, reducing efficacy. In this study, four adjuvants were selected to improve the diffusion and adhesion of bifenthrin droplets on the surface of tea leaves at different growth stages. The coupling effect of bifenthrin and adjuvants on the time-dependent and concentration-dependent wettability of droplets was investigated, and the difference in the wettability between bud and leaf was explained by observing the surface morphology. It was found that adjuvants effectively reduced the contact angle of droplets and accelerated the diffusion speed, and the above phenomenon became obvious with the increase in the adjuvant concentration. The wetting promotion of young leaves was more significant due to the reduced epicuticle wax and the greater roughness compared with fresh buds. The surface tension of the pesticide mixture was negatively correlated with the cosine of contact angle after adding the four adjuvants regardless of the growth stage of tea leaves. The contact angle of 0.2% Silwet L-77 decreased to 0° within 10 s, but the extreme wettability led to the decrease in adhesion with the increase in concentration. However, the wettability and adhesion on the surface of tea leaves were simultaneously suitable with more than 0.1% nonionic surfactant. The minimum concentration of the optimal adjuvant proposed in this study can provide an experimental basis and guide more efficient plant protection in tea gardens.

Surface properties of Tetranychus urticae Koch (Acari: Tetranychidae) and the effect of their infestation on the surface properties of kidney bean (Phaseolus vulgaris L.) hosts

BACKGROUND

The wettability of the target surfaces affects the wetting and deposition of pesticides on them. The properties of leaf surfaces change after infestation by Tetranychus urticae Koch. Studying the surface wettability of T. urticae and the changes in leaf wettability after infestation is important to guide the use of acaricides.

RESULTS

The body surface of T. urticae is an ellipsoidal crown covered with dense cuticle striations and hairs arranged in different directions, which makes the surface of T. urticae rough and hydrophobic. The abaxial surfaces of the leaves are rougher and more hydrophobic than the adaxial surfaces. After infestation by T. urticae, the faded spots were sunken on the adaxial surface and raised on the abaxial surface, where they had formed new wide peaks and valleys. The adaxial surface became obviously rougher and more hydrophobic, while the roughness of the abaxial surface became slightly larger, and the change in hydrophobicity was not obvious. The contact angles of the studied commercial acaricide on these surfaces were greater than 65° and were affected by the infestation. Reducing the surface tension can allow for better wetting of these surfaces and eliminate changes in leaf wettability.

CONCLUSION

The surfaces of kidney bean leaves became more hydrophobic after infestation by T. urticae with hydrophobic surface. The wettability of the acaricide solution should be adjusted according to the changes in leaf wettability. This study has important theoretical guiding significance for improving effective deposition of acaricide.

Performance matching between the surface structure of cucumber powdery mildew in different growth stages and the properties of surfactant solution

BACKGROUND

Understanding performance matching of pesticide droplets on the surface of cucumber leaves modified by powdery mildew is of practical importance for the agricultural sector. Here, the surface texture and wettability of cucumber leaves covered by powdery mildew were systematically examined using parameters such as micromorphology, physicochemical properties, and liquid droplet contact angle measurements.

RESULTS

Our results show that powdery mildew growth can be divided into four distinct stages according to the surface texture characteristics of the diseased cucumber leaves. The three-dimensional (3D) surface structures of powdery mildew layers on cucumber leaves had individual characteristics at different mildew growth stages, among which powdery mildew was more easily spread in the last growth stage, and powdery mildew height was greatest in the NO. 2 growth stage (S_a  = 425.35 μm). Surface free energy values, static contact angle, and contact angle hysteresis all correlated strongly with the surface characteristics of powdery mildew layers at different growth stages. When the concentration of surfactant reached the critical micelle concentration, the wetting state of AEO-5 solution droplets on the surface of cucumber powdery mildew leaves reached the Wenzel state more easily. The wettability of a droplet on the leaf surface depends on the state of the monomer and micelle in the surfactant solution and the surface characteristics of the powdery mildew-covered leaf.

CONCLUSION

The 3D structure and relative dielectric constant of powdery mildew-covered leaves influenced surface texture characteristics, which in turn controlled the wetting and matching ability of surfactant droplets on diseased leaves. This work provides valuable new insights into the matching of the structure of powdery mildew-covered plant leaves with the properties of surfactant solutions. © 2021 Society of Chemical Industry.

Impact of the equilibrium relationship between deposition and wettability behavior on the high-efficiency utilization of pesticides

BACKGROUND

Often, due to the occurrence of powdery mildew, cucumber leaf surfaces is changed into a more hydrophobic surface, which affects wetting and spreading of liquid pesticides, reducing their efficiency. The wetting and deposition behavior of liquid pesticides can be improved by adding surfactants to pesticides. Added surfactants affect the spray volume of the pesticide, which can lead to waste and a low utilization rate of the pesticide. It is important to further balance the relationship between deposition and wettability of pesticide liquid on the surfaces of healthy leaves and powdery mildew leaves of cucumber.

RESULTS

This study evaluated the deposition and wettability of hexaconazole (Hexa) with surfactants on the surfaces of healthy leaves and powdery mildew leaves of cucumber. The deposition rates of Hexa with surfactants were lower than that of Hexa due to the loss of solution in conventional spray volume (750 L ha^-1 ). The deposition rate of Hexa did not necessarily increase with increasing spray volume, and the deposition rate did not increase again after the spray volume increased to a certain level. Under the condition that the prevention and control effect were not reduced, we found that the volume of solution spray with added Silwet618 or AEO-5 should be adjusted to half of the normal volume, while the volume of solution spray with added 1227 or rosin-based quarternary ammonium should be adjusted to two-thirds of the normal volume to increase the deposition rate by approximately 30%. Regarding the wetting parameters, the results showed that the wettability of Hexa with Silwet618 was the best, but their combination was not ideal according to the composite index and deposition. By analyzing all the parameters, it was found that the spray volume reduction of Hexa with surfactant was approximately equal to the solution surface tension reduction, compared with the parameters of Hexa.

CONCLUSION

The equilibrium relationship between deposition rate and wetting parameters was determined to provide guidance for the application of surfactants and to lower the dosage of pesticides to increase their efficiency and reduce their application. © 2021 Society of Chemical Industry.

Fiber-Templated 3D Calcium-Phosphate Scaffolds for Biomedical Applications: The Role of the Thermal Treatment Ambient on Physico-Chemical Properties

A successful bone-graft-controlled healing entails the development of novel products with tunable compositional and architectural features and mechanical performances and is, thereby, able to accommodate fast bone in-growth and remodeling. To this effect, graphene nanoplatelets and Luffa-fibers were chosen as mechanical reinforcement phase and sacrificial template, respectively, and incorporated into a hydroxyapatite and brushite matrix derived by marble conversion with the help of a reproducible technology. The bio-products, framed by a one-stage-addition polymer-free fabrication route, were thoroughly physico-chemically investigated (by XRD, FTIR spectroscopy, SEM, and nano-computed tomography analysis, as well as surface energy measurements and mechanical performance assessments) after sintering in air or nitrogen ambient. The experiments exposed that the coupling of a nitrogen ambient with the graphene admixing triggers, in both compact and porous samples, important structural (i.e., decomposition of β-Ca3(PO4)2 into α-Ca3(PO4)2 and α-Ca2P2O7) and morphological modifications. Certain restrictions and benefits were outlined with respect to the spatial porosity and global mechanical features of the derived bone scaffolds. Specifically, in nitrogen ambient, the graphene amount should be set to a maximum 0.25 wt.% in the case of compact products, while for the porous ones, significantly augmented compressive strengths were revealed at all graphene amounts. The sintering ambient or the graphene addition did not interfere with the Luffa ability to generate 3D-channels-arrays at high temperatures. It can be concluded that both Luffa and graphene agents act as adjuvants under nitrogen ambient, and that their incorporation-ratio can be modulated to favorably fit certain foreseeable biomedical applications.

Active coatings of thermoplastic starch and chitosan with alpha-tocopherol/bentonite for special green coffee beans

The quality of green coffee beans (GCBs) is possibly affected by storage conditions. Edible polymer coatings for GCBs can help preserve flavors and improve shelf life of GCBs. This study aimed to incorporate α-tocopherol, a powerful antioxidant, in thermoplastic starch [TPS] and chitosan [TPC] and determined the best cavitation energy (960-3840 J·mL-1) using an ultrasonic probe. Then, we evaluated the incorporation of bentonite (0% and 2% m/m) and α-tocopherol (0% and 10% m/m) in the best energy cavitation/biopolymer combination. The TPS and TPC coatings demonstrated good adherence to the GCBs, measured by surface energy. The dispersion of α-tocopherol in TPC, with cavitation energy 960 J·mL-1, promoted greater stability (greater zeta potential), thereby increasing antioxidant activity by 28% compared to TPS, therefore, was selected for a second stage. Incorporation of 2% bentonite into the TPC, with 10% α-tocopherol, resulted in a 3.7 × 10-10 g·m-1·s-1·Pa-1 water vapor permeability, which is satisfactory for prevented of moisture gain during storage. The compressive load showed values of 375 N to the non-coated GCB and around 475 N with the insertion of coatings to the GCB. Thus, a TPC/α-tocopherol/bentonite combination, dispersed with 960 J·mL-1 energy, was highly effective in the development of biopolymeric coatings for the GCBs.

Tumor microenvironment-responsive, high internal phase Pickering emulsions stabilized by lignin/chitosan oligosaccharide particles for synergistic cancer therapy

HYPOTHESIS

The stability of anti-cancer drugs and the adverse drug reactions (ADRs) caused by drug-drug interactions (DDIs) are two major challenges of combination chemotherapy. In this work, hydrophilic drug loaded lignin-based nanoparticles were applied to stabilize high internal phase Pickering emulsions (HIPPEs) containing hydrophobic drug in the oil phase, which not only improved the stability of anti-cancer drugs, but also reduced the risk of DDIs.

EXPERIMENTS

Highly biocompatible enzymatic hydrolysis lignin/chitosan oligosaccharide (EHL/COS-x) nanoparticles were prepared and used to load hydrophilic cytarabine (Ara-C). The morphology, loading capacity, encapsulation efficiency and emulsifying properties of nanoparticles were characterized and predicted. Subsequently, these nanoparticles were applied to stabilize HIPPEs with soybean oil containing hydrophobic curcumin as dispersed phase. The effects of the morphology, amphipathy and concentration of nanoparticles and oil/water ratio on the microstructure and stability of HIPPEs were investigated. Meanwhile, the controlled release, protective performance, cytotoxicity and bio-activity of HIPPEs were also evaluated.

FINDINGS

EHL/COS-x nanoparticles loaded with Ara-C could stabilize HIPEs with 85 vol% soybean oil containing curcumin. The two drugs were separately loaded in same delivery system, which effectively lowered the risk of DDIs. Meanwhile, HIPPEs provided outstanding UV, thermal and oxidation protection for these two environmentally sensitive anti-cancer drugs. In addition, HIPPEs displayed a good pH-responsive release in a tumor environment. In vitro experiments show that the killing efficiency of two drugs co-loaded HIPPEs against the leukemia cell is two times higher than that of single drug loaded systems. This strategy can be extended to the synergistic therapy of two or more drugs with different physicochemical properties.

Eco-Friendly Castor Oil-Based Delivery System with Sustained Pesticide Release and Enhanced Retention

The deposition of pesticides and their retention on plant surfaces are critical challenges for modern precision agriculture, which directly affect phytosanitary treatment, bioavailability, efficacy, and the loss of pesticides. Herein, a novel and eco-friendly waterborne polyurethane delivery system was developed to enhance the spray deposition and pesticide retention on plant surfaces. More specifically, biobased cationic and anionic waterborne polyurethane dispersions were synthesized from castor oil. Both cationic and anionic polyurethane dispersions exhibited remarkable microstructural, amphiphilic, and nanoparticle morphologies with a core-shell structure that served to encapsulate a biopesticide (azadirachtin) in their hydrophobic cores (WPU-ACT). The results indicated that the cationic WPU-ACT carriers exhibited a better sustained release behavior and a better protective effect from light and heat for azadirachtin. In addition, the simultaneous spray of anionic and cationic WPU-ACT significantly enhanced the spray deposition and prolonged the retention of pesticides due to the reduced surface tension and surface precipitation induced by the electrostatic interaction when two droplets with opposite charges come into contact with each other. A field efficacy assessment also indicated that the simultaneous spray of anionic and cationic WPU-ACT could control the infestation of brown planthopper in rice crops. Castor oil-based waterborne polyurethanes in this study work as an efficient pesticide delivery system by exhibiting enhanced deposition, rainfastness, retention ability, protection, and sustained release behavior, holding great promise for spraying pesticide formulations in modern and environmentally friendly agricultural applications.

Role of Adjuvants in the Management of Anthracnose-Change in the Crystal Morphology and Wetting Properties of Fungicides

The hydrophobic wax layer of pepper fruit (Capsicum frutescens L.) increases the importance of selecting adjuvants that improve the wetting property of droplets on the target organism and increase the effective utilization of fungicides. In this study, the effect of adjuvants including nonionic, cationic, organosilicone, and oils on the wettability of fungicides was determined. The critical micelle concentrations for S903 (organosilicone), 1227 (cationic), AEO-5 (nonionic), GY-Tmax (oil), and XP-2 (oil) were 25, 1000, 100, 200, and 500 mg/L, respectively. Interface behaviors and in vivo tests suggested that adjuvants at appropriate concentrations (S903, 2.5 mg/L; 1227, 100 mg/L; AEO-5, 1 mg/L; GY-Tmax, 50 mg/L; and XP-2, 5 mg/L) resulted in optimum efficiency. Adjuvants significantly increased the inhibitory activity of pyraclostrobin against the mycelial growth, spore germination, and germ tube elongation of Colletotrichum scovillei by 41.3-58.8%, 28.2-44.6%, and 27.8-39.8%, respectively. Pyraclostrobin amended with S903 and XP-2 showed higher efficacy against anthracnose than the fungicide alone on pepper fruit. The increased efficacy may have resulted from the changed crystal morphology (ellipses of similar sizes), improved wettability, and rainfastness. A structural equation model indicated that surface tension and retention play the most important roles in the application properties of fungicide. In field experiments, the efficacy of pyraclostrobin with adjuvants showed no significant difference with pyraclostrobin alone, which indicated that, except for adjuvants, other spraying technologies are important for improving the field performance of fungicides. These results provide a foundation for the synthesis of highly efficient fungicides based on crystal structure and for the sustainable management of pepper anthracnose.

Oil Adjuvants Enhance the Efficacy of Pyraclostrobin in Managing Cucumber Powdery Mildew (Podosphaera xanthii) by Modifying the Affinity of Fungicide Droplets on Diseased Leaves

Adding adjuvants improved the affinity of fungicide droplets to cucumber leaves infected with powdery mildew (Podosphaera xanthii) and subsequent efficacy of fungicide treatments in reducing the disease. The affinity of oil adjuvants was quantified by adhesional tension and "work of adhesion". Oil adjuvant-fungicide mixtures were applied to plants in field experiments to evaluate their effectiveness in disease prevention. Both the adhesional tension and work of adhesion of the adjuvants at selected concentrations increased on powdery-mildew-infected cucumber leaves more than on healthy cucumber leaves. The adjuvant GY-Tmax (GYT) displayed the best surface activity or "surfactivity" in enhancing the affinity and adherence of droplets to powdery-mildew-infected cucumber leaves, while epoxidized soybean oil (ESO), methyl oleate, and biodiesel exhibited much lower effects in terms of the surface tension, contact angle, adhesional tension, and work of adhesion. Field experiments determined that the combination of GYT at 1,000 mg liter^-1 and pyraclostrobin (150 g a.i. ha^-1) was most effective (91.52%) in controlling cucumber powdery mildew. Pyraclostrobin with ESO was also highly effective (ranging from 77.54 to 89.65%). The addition of oil adjuvants, especially GYT and ESO, to fungicide applications can be an effective strategy to enhance the efficacy of pesticides in controlling plant diseases by modifying the affinity of fungicide droplets to symptomatic leaves.

Wettability of pear leaves from three regions characterized at different stages after flowering using the OWRK method

BACKGROUND

A better understanding of leaf surface wettability is critical to improve the adhesion of liquid pesticides. Leaf surface wettability is dependent on the property of the liquid as well as the physical and chemical properties of the leaf, which vary with climate and growth stage. The aim of this study was to characterize the wettability of pear leaves from three different climatic regions at different stages after flowering.

RESULTS

The contact angles of different test liquids were measured on both adaxial and abaxial pear leaf surfaces and the Owens-Wendt-Rabel-Kaelble (OWRK) method was used to calculate surface free energy (SFE) and its polar and non-polar components. The results demonstrated that the SFE of both the adaxial and abaxial surface of the pear leaf, and the proportion of polar component, increased with increasing time after flowering. At early growth stages, pear leaves were highly hydrophobic, similar to a polytetrafluoroethylene surface, whereas at later growth stages, pear leaves were hydrophobic, more similar to a polymethylmethacrylate surface. Also, the SFE differed with climatic region. Factors influencing these changes are discussed.

CONCLUSION

Changes in contact angles and SFE correlated with the change of the leaf surface wettability. Leaves became easier to wet (higher SFE), with an overall increasing polar component to the surface, with increasing age after flowering. As expected, changes in wettability were found in pear leaves at different stages after flowering and in different regions (P < 0.05). Pear leaves from Yuanping were easier to wet than leaves from Yuci and Linyi, and adaxial surfaces were easier to wet than abaxial surfaces. These results provide beneficial information for the application of agrochemicals for improved wetting and spreading behavior. © 2018 Society of Chemical Industry.

Determination of surface energies of hot-melt extruded sugar-starch pellets

Hot-melt extruded sugar-starch pellets are an alternative for commercial sugar spheres, but their coating properties remain to be studied. Both the European Pharmcopoeia 8.6 and the United States Pharmacopoeia 40 specify the composition of sugar-starch pellets without giving requirements for the manufacturing process. Due to various fabrication techniques, the physicochemical properties of pellets may differ. Therefore, the adhesion energies of three coating dispersions (sustained, enteric and immediate release) on different types of pellets were investigated. In this context, the surface energies of various kinds of corn starch (normal, waxy, high-amylose) and sucrose pellets were analyzed using the sessile drop method, whereas the surface tensions of the coating dispersions were examined using the pendant drop method. The adhesion forces were calculated from the results of these studies. Furthermore, sugar spheres were characterized in terms of particle size distribution, porosity and specific surface area. An increase of the pellets' sucrose content leads to a more porous surface structure, which gives them an enhanced wetting behavior with coating dispersions. The adhesion energies of extruded sugar-starch pellets are similar to those of commercial sugar spheres, which comply with pharmacopeial requirements. Both types of pellets are equally suited for coating.

Methods for evaluating leaf surface free energy and polarity having accounted for surface roughness

BACKGROUND

Leaf surfaces can have similar wettability, while their roughness and polarity may be very different. This may affect agrochemical bioefficacy, hence there is a need to characterise leaf surface polarity and roughness separately. This paper reviews established surface evaluation techniques and then uses a comprehensive dataset of static contact angles (12 chemical solutions on 15 different species) to compare and contrast them for their ability to characterise leaf surface polarity in isolation from roughness.

RESULTS

Many techniques were severely limited when applied to leaf surfaces. A failing of the surface free energy (SFE) concept is that both physical and chemical properties affect the SFE. Additionally, whilst the leaf surface chemistry does not change, the SFE values generated are dependent on the chemical properties of the probe solution employed.

CONCLUSIONS

The wetting tension-dielectric (WTD) method stands out due to its ability to isolate and quantify leaf surface roughness and polarity. A novel (WTD) roughness correction factor is proposed to improve SFE determination. The strong correlation between leaf polarity and leaf wettability for polar solutions (such as water) makes the WTD method a valuable tool for the evaluation of leaf surface-droplet behaviour and the advancement of agrochemical spray formulation technologies. © 2017 Society of Chemical Industry.

The wetting behavior of aqueous surfactant solutions on wheat (Triticum aestivum) leaf surfaces

In this research the wetting behavior of agro-surfactant solutions (Triton X-100, SDS, DTAB) on wheat leaf surfaces have been investigated based on the surface free energy, surface tension, and the contact angle. The results show that the contact angle of those surfactant solutions keeps constant with low adsorption at interfaces below 1 × 10^-5 mol L^-1. With the increase in concentration, the contact angles of Triton X-100 decrease sharply because the adsorption of molecules at solid-liquid interfaces (Γ_SL') is several times greater than that at liquid-air interfaces (Γ_LV). With regards to SDS and DTAB, the contact angle also decreases but is even larger than 90° above the CMC, while the ratio of Γ_SL' to Γ_LV is about 1.20, demonstrating that the Gibbs surface excess is related to the structure of surfactant molecules. Obviously, besides the properties of wheat leaf surfaces and surfactant solutions, the wetting behavior mainly depends on their noncovalent interactions. Among these, the hydrophobic interaction is the main force promoting molecules to adsorb on the surface, with the assistance of the Lifshitz-van der Waals interactions and the electrostatic interactions. According to the mechanism of their wetting behavior on plant surfaces, the recipe of pesticide formulation can be adjusted with better wettability to reduce its loss, consequently improving pesticide utilization and decreasing environmental contamination.