Herbicide Deposition on Leaf Surfaces

Weed Science ◽  
1990 ◽  
Vol 38 (3) ◽  
pp. 280-288 ◽  
Author(s):  
F. Dan Hess ◽  
Richard H. Falk

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.

2016 ◽  
Vol 38 (2) ◽  
pp. 215 ◽  
Author(s):  
Glenda Quaresma Ramos ◽  
Marta Duarte da Fonseca de Albuquerque ◽  
José Luiz Pinto Ferreira ◽  
Eduardo Adriano Cotta ◽  
Henrique Duarte da Fonseca Filho

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. 


2017 ◽  
Vol 8 ◽  
pp. 2345-2356 ◽  
Author(s):  
Oliver Hagedorn ◽  
Ingo Fleute-Schlachter ◽  
Hans Georg Mainx ◽  
Viktoria Zeisler-Diehl ◽  
Kerstin Koch

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.


Weed Science ◽  
2006 ◽  
Vol 54 (1) ◽  
pp. 16-22 ◽  
Author(s):  
Debanjan Sanyal ◽  
Prasanta C. Bhowmik ◽  
Krishna N. Reddy

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.


Weed Science ◽  
1974 ◽  
Vol 22 (4) ◽  
pp. 394-401 ◽  
Author(s):  
F. D. Hess ◽  
D. E. Bayer ◽  
R. H. Falk

The distribution pattern of MCPA ([(4-chloro-o-tolyl)oxy] acetic acid) on leaf surfaces of three species was studied using the cathodoluminescence detection mode of a scanning electron microscope. On low-wax-content sugarbeet (Beta vulgarisL.) leaves MCPA concentrated in the depressions over the anticlinal cell walls when applied at high volumes (748 and 374 L/ha). At low volumes (23 L/ha), numerous small deposits of MCPA were randomly distributed over both anticlinal and periclinal walls. These distinct patterns were independent of herbicide concentration. Regardless of spray volumes, MCPA remaining on the waxy leaf surfaces of cabbage (Brassica oleraceaL.) coalesced into small thick deposits. Large spray drops from high application volumes shattered on impact with the stellate hairs of turkey mullein (Eremocarpus setigerusBenth.) resulting in some MCPA reaching the leaf surface. Spray drops from low application volumes did not shatter but lodged on the hairs with very little reaching the leaf surface.


2021 ◽  
Vol 64 (6) ◽  
pp. 1883-1894
Author(s):  
JohnPaul R. Abbott ◽  
Heping Zhu ◽  
Hongyoung Jeon

HighlightsRetention and spread of droplets with seven adjuvants were investigated on flat leaves.Surface tension of spray solutions, leaf wettability, and roughness strongly affected droplet retention and spread.Complete droplet retention occurred on hydrophilic leaves with all adjuvants and concentrations.High retention and spread on superhydrophobic leaves were achieved with the organo-silicone adjuvant.No retention occurred on superhydrophobic leaf surfaces with the hydrocolloid polymer adjuvant.Abstract. To optimize spray application efficiency, it is necessary to understand how the addition of adjuvants modifies the deposition properties of spray droplets on leaf surfaces due to variations in adhesive characteristics, such as roughness and wettability. Retention and spread of droplets with seven commercially available adjuvants were tested and compared at different concentrations. Tests were conducted with three leaf surfaces ranging in roughness and wettability from very smooth and hydrophilic to very rough and superhydrophobic. The adjuvants were formulated with non-ionic surfactant, crop oil, seed oil, organo-silicone, hydrocolloid polymer, or combinations of these agents as primary ingredients. Droplets of approximately 340 µm diameter were emitted from a streamed mono-sized generator. Droplet impact and spread were recorded with a 3D imaging system consisting of three high-speed digital cameras and analyzed using 3D motion analysis software. Retention and spread were determined by comparing droplet liquid volumes and droplet cross-sectional areas before and after impact, respectively. The surface tension of spray solutions and wettability of leaf surfaces strongly affected droplet retention. Droplets with lower surface tension were more likely to achieve high retention than those with higher surface tension. Droplet retention generally decreased with increasing leaf roughness-wettability. All droplets with and without adjuvants achieved 100% retention on the hydrophilic leaf surface. Addition of non-ionic, oil, or organo-silicone based adjuvants in the spray solution improved droplet retention on hydrophobic leaves, while the organo-silicone based adjuvant achieved the highest retention on superhydrophobic leaf surfaces. Droplet retention with the hydrocolloid polymer adjuvant was generally comparable to the other six adjuvants on the hydrophilic leaves and on the hydrophobic leaves with intermediate roughness and wettability but failed to achieve any retention on the superhydrophobic leaves. To improve droplet retention and adhesion, selection of adjuvants representing the non-ionic, oil, organo-silicone, blended, or hydrocolloid-based additives for enhancing spray solution performance must comply with the leaf surface characteristics. Keywords: Droplet rebound, High-speed imaging, Leaf wettability, Pesticide droplet deposition, Topography parameters.


1994 ◽  
Vol 72 (9) ◽  
pp. 1379-1386 ◽  
Author(s):  
Mahesh K. Upadhyaya ◽  
Nancy H. Furness

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.


1993 ◽  
Vol 7 (3) ◽  
pp. 706-716 ◽  
Author(s):  
Thomas A. Bewick ◽  
Donn G. Shilling ◽  
Robert Querns

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.


2017 ◽  
Vol 51 ◽  
pp. 274-280
Author(s):  
A. D. Potemkin ◽  
Yu. S. Mamontov ◽  
N. S. Gamova

Study of selected specimens of Gymnomitrion collected by D. G. Long in Yunnan, China, revealed a new species, G. fissum Mamontov et Potemkin, sp. nov., with a fissured leaf surface. Comparison of SEM images of the leaf surface and leaf cross sections shows that the leaf surface of G. fissum is different from that of other known species with a superficially similar leaf surface, i. e. Mylia taylorii, M. verrucosa s. l. and Trabacellula tumidula. It has fissures around the cell lumen rather than grids and perforations. Outer cell walls of Gymnomitrion fissum are much thicker than in Mylia taylorii, M. verrucosa s. l. and Trabacellula tumidula, and their outer layers tend to be partly or completely caducous. G. fissum is related to the group of species assigned to the former genus Apomarsupella.


2021 ◽  
Author(s):  
Noa Ligot ◽  
Benoît Pereira ◽  
Patrick Bogaert ◽  
Guillaume Lobet ◽  
Pierre Delmelle

<p>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.</p><p>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 (≤ 90, 90-125, 125-250, 250-500, 500-1000, 1000-2000 µm) 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<sup>-2 </sup>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.</p><p>Our results show that leaf coverage by ash increases with decreasing particle size. Exposure of tomato and chilli pepper to ash ≤ 90 μm always led to ~90% coverage of the leaf surface area. For coarser particles sizes (i.e. between 125 and 500 µm) 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 µm, wetting of the leaf surfaces prior to ashfall enhanced the ash cover by 19 ± 5% and 34 ± 11% for tomato and chilli pepper, respectively.</p><p>These findings highlight that ash deposit thickness alone cannot describe the hazard intensity accurately. A thin deposit of fine ash (≤ 90 µm) 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.</p>


2009 ◽  
Vol 72 (10) ◽  
pp. 2028-2037 ◽  
Author(s):  
GUODONG ZHANG ◽  
LI MA ◽  
LARRY R. BEUCHAT ◽  
MARILYN C. ERICKSON ◽  
VANESSA H. PHELAN ◽  
...  

Survival and internalization characteristics of Escherichia coli O157:H7 in iceberg, romaine, and leaf lettuce after inoculation of leaf surfaces and soil were determined. A five-strain mixture of E. coli O157:H7 in water and cow manure extract was used as an inoculum for abaxial and adaxial sides of leaves at populations of 6 to 7 log and 4 log CFU per plant. The five strains were individually inoculated into soil at populations of 3 and 6 log CFU/g. Soil, leaves, and roots were analyzed for the presence and population of E. coli O157:H7. Ten (4.7%) of 212 samples of leaves inoculated on the adaxial side were positive for E. coli O157:H7, whereas 38 (17.9%) of 212 samples inoculated on the abaxial side were positive. E. coli O157:H7 survived for at least 25 days on leaf surfaces, with survival greater on the abaxial side of the leaves than on the adaxial side. All 212 rhizosphere samples and 424 surface-sanitized leaf and root samples from plants with inoculated leaves were negative for E. coli O157:H7, regardless of plant age at the time of inoculation or the location on the leaf receiving the inoculum. The pathogen survived in soil for at least 60 days. Five hundred ninety-eight (99.7%) of 600 surface-sanitized leaf and root samples from plants grown in inoculated soil were negative for E. coli O157:H7. Internalization of E. coli O157:H7 in lettuce leaves and roots did not occur, regardless of the type of lettuce, age of plants, or strain of E. coli O157:H7.


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