Amount Of Epicuticular Wax Research Articles

Project ChemicalBlooms: Collaborating with citizen scientists to survey the chemical diversity and phylogenetic distribution of plant epicuticular wax blooms.

Plants use chemistry to overcome diverse challenges. A particularly striking chemical trait that some plants possess is the ability to synthesize massive amounts of epicuticular wax that accumulates on the plant's surfaces as a white coating visible to the naked eye. The ability to synthesize basic wax molecules appears to be shared among virtually all land plants, and our knowledge of ubiquitous wax compound synthesis is reasonably advanced. However, the ability to synthesize thick layers of visible epicuticular crystals ("wax blooms") is restricted to specific lineages, and our knowledge of how wax blooms differ from ubiquitous wax layers is less developed. Here, we recruited the help of citizen scientists and middle school students to survey the wax bloom chemistry of 78 species spanning dicot, monocot, and gymnosperm lineages. Using gas chromatography-mass spectrometry, we found that the major wax classes reported from bulk wax mixtures can be present in wax bloom crystals, with fatty acids, fatty alcohols, and alkanes being present in many species' bloom crystals. In contrast, other compounds including aldehydes, ketones, secondary alcohols, and triterpenoids were present in only a few species' wax bloom crystals. By mapping the 78 wax bloom chemical profiles onto a phylogeny and using phylogenetic comparative analyses, we found that secondary alcohol and triterpenoid-rich wax blooms were present in lineage-specific patterns that would not be expected to arise by chance. That finding is consistent with reports that secondary alcohol biosynthesis enzymes are found only in certain lineages but was a surprise for triterpenoids, which are intracellular components in virtually all plant lineages. Thus, our data suggest that a lineage-specific mechanism other than biosynthesis exists that enables select species to generate triterpenoid-rich surface wax crystals. Overall, our study outlines a general mode in which research scientists can collaborate with citizen scientists as well as middle and high school classrooms not only to enhance data collection and generate testable hypotheses but also to directly involve classrooms in the scientific process and inspire future STEM workers.

Suplementação do silício aumenta a regeneração in vitro de embriões somáticos de palma de óleo (Elaeis guineensis Jacq.)

ABSTRACT The use of silicates in plant tissue culture has resulted in positive effects regarding the morphological, anatomical and physiological characteristics of in vitro plants. However, biological responses to this mineral are dose and genotype dependent. The objective of the present study was to evaluate the influence of silicon supplementation on the somatic embryogenesis of oil palm (Elaeis guineensis Jacq.). The study was carried out in three stages of the cloning process, namely: Regeneration (i) and germination (ii) of somatic embryos and during ex vitro acclimatization (iii) of regenerated plantlets. The culture media were supplemented with four doses (0.0, 0.5, 1.0 and 1.5 g L-1) of calcium silicate (CaSiO3). The resulting plantlets were transplanted and acclimatized in a greenhouse. The regression analysis showed that the dose of 0.63g L-1 of CaSiO3 induced a higher rate of regeneration, which would allow a 58% increase in the number of somatic embryos formed. However, the germination of the plantlets, as well as their morphometric characters, were not affected by the different doses of CaSiO3, although the presence of this compound promoted an increase in the thickness of the epidermis and a reduction in the amount of epicuticular wax. Overall, silicon does contribute to the cloning of E. guineensis.

Respuesta de Commelina erecta L. a dos formulados de glifosato, y rol del almidón y de las ceras epicuticulares en la sensibilidad al glifosato

The aim of this study was to evaluate the effects of two formulations of glyphosate on adult plants and seedlings of Commelina erecta L., and to determine whether stem starch storage and epicuticular waxes of leaves are involved in plant sensitivity to this herbicide. The formulations used were isopropylamine salt (IPA) and diammonium salt (DA). All measured growth parameters and chlorophyll were negatively affected by both formulations. The IPA formulation showed a higher decrease in the branching rate and phyllochron, whereas the DA formulation showed a higher decrease in the elongation rate, chlorophyll content at 48 hours after application in adult plants, and the starch proportion in the stem basal section, and caused more leaf injuries. All plants of C. erecta presented starch storage in the both stem section. After glyphosate application, stem starch proportion of the basal section evolved differently in both growth stages, whereas stem starch proportion of the apical section showed an irregular variation. The amount of epicuticular waxes was higher in adult plants. These results show that both glyphosate formulations are ineffective for the management of C. erecta. The low sensitivity to glyphosate in C. erecta, especially in plants higher than five leaves, could be related to starch storage in stem and epicuticular waxes on leaves.

Phenotypic Variation for Epicuticular Waxes Across Plant Introductions of Onion

The amounts and types of epicuticular waxes on onion (Allium cepa) leaves affect feeding damage by onion thrips (Thrips tabaci), a serious insect pest of onion. This study used gas chromatography mass spectrometry (GCMS) to measure amounts of epicuticular waxes on foliage of two plants from each of 50 plant introductions (PI) and inbred lines with high (waxy) and low (glossy) amounts of wax. Wax amounts on leaves of the same plants were measured twice (once in the greenhouse and once after moving plants outside) and were significantly (P < 0.01) correlated; however, wax amounts on leaves of plants grown in the greenhouse were approximately twice that of the same plants grown outside. Hentriacontanone-16 (H16) was the predominant wax on leaves of all PIs except PI 289689, and amounts of H16 were significantly correlated with amounts of fatty alcohols and total wax. Five plants from 17 of the PIs were grown in the greenhouse, wax amounts measured using GCMS, and results were significantly correlated with earlier evaluations. Results indicate that measurements of waxes on onion foliage should occur under protected conditions to better characterize phenotypic variation, and selection of higher amounts of waxes other than H16 may be effective toward the development onions suffering less thrips damage.

Phyto-cleaning of particulate matter from polluted air by woody plant species in the near-desert city of Jodhpur (India) and the role of heme oxygenase in their response to PM stress conditions.

Particulate matter (PM) is one of the most dangerous pollutants in the air. Urban vegetation, especially trees and shrubs, accumulates PM and reduces its concentration in ambient air. The aim of this study was to examine 10 tree and shrub species common for the Indian city of Jodhpur (Rajasthan) located on the edge of the Thar Desert and determine (1) the accumulation of surface and in-wax PM (both in three different size fractions), (2) the amount of epicuticular waxes on foliage, (3) the concentrations of heavy metals (Cd and Cu) on/in the leaves of the examined species, and (4) the level of heme oxygenase enzyme in leaves that accumulate PM and heavy metals. Among the investigated species, Ficus religiosa L. and Cordia myxa L. accumulated the greatest amount of total PM. F. religiosa is a tall tree with a lush, large crown and leaves with wavy edge, convex veins, and long petioles, while C. myxa have hairy leaves with convex veins. The lowest PM accumulation was recorded for drought-resistant Salvadora persica L. and Azadirachta indica A. Juss., which is probably due to their adaptation to growing conditions. Heavy metals (Cu and Cd) were found in the leaves of almost every examined species. The accumulation of heavy metals (especially Cu) was positively correlated with the amount of PM deposited on the foliage. A new finding of this study indicated a potentially important role of HO in the plants' response to PM-induced stress. The correlation between HO and PM was stronger than that between HO and HMs. The results obtained in this study emphasise the role of plants in cleaning polluted air in conditions where there are very high concentrations of PM.

Seasonal variations in the amount of black carbon particles deposited on the leaf surfaces of nine Japanese urban greening tree species and their related factors

As black carbon (BC) particles can be deposited on the leaf surfaces, urban greening is considered to be effective in purifying urban air. However, little information on the seasonal variations in the amount of BC particles deposited on the leaf surfaces (BC amount on the leaves) is available in Japanese urban greening tree species. Therefore, we investigated seasonal variations in the BC amount on the leaves of evergreen (Quercus glauca, Quercus myrsinaefolia, Osmanthus fragrans and Ilex rotunda) and deciduous (Zelkova serrata, Styrax japonica, Magnolia kobus, Cornus kousa and Cornus florida) broad-leaved tree species. The BC amount on the leaves tended to increase from April for different periods, and then reached a saturated state in the tree species, excluding M. kobus. In the 4 evergreen broad-leaved trees, the seasonal variation was positively correlated with the atmospheric concentration of BC particle. In the 5 deciduous broad-leaved trees, the seasonal variation was negatively and positively correlated with the water-repellence (water droplet contact angle) and the amount of epicuticular wax on the leaf surface, respectively. Therefore, the BC amounts on the leaves of evergreen and deciduous broad-leaved urban tree species are considered to be mainly regulated by environmental factors and leaf surface characteristics, respectively.

Molecular, chemical, and physiological analyses of sorghum leaf wax under post-flowering drought stress

Wax accumulation on the sorghum surface plays an important role in drought tolerance by preventing non-stomatal water loss. Thereby, the effect of post-flowering drought stress (PFDS) on the epicuticular wax (EW) amount, relative water content (RWC), chlorophyll, and grain yield in sorghum drought contrasting genotypes were investigated. The experiment was conducted as a split-plot based on randomized complete block design (RCBD) with two water treatments (normal watering and water holding after 50% flowering stage), and three genotypes (Kimia and KGS23 as drought-tolerant and Sepideh as drought-susceptible). Scanning electron microscopy and GC-MS analyses were used to determine the wax crystals density and its compositions, respectively. In addition, based on literature reviews and publicly available datasets, six wax biosynthesis drought stress-responsive genes were chosen for expression analysis. The results showed that the amounts of EW and wax crystals density were increased in Kimia and Sepideh genotypes and no changed in KGS23 genotype under drought stress. Chemical compositions of wax were classified into six major groups including alkanes, fatty acids, aldehydes, esters, alcohols, and cyclic compounds. Alkanes increment in drought-tolerant genotypes led to make an effective barrier against the drought stress to control water losses. In addition, the drought-tolerant genotypes had higher levels of RWC compared to the drought-susceptible ones, resulted in higher yield produced under drought condition. According to the results, SbWINL1, FATB, and CER1 genes play important roles in drought-induced wax biosynthesis. The results of the present study revealed a comprehensive view of the wax and its compositions and some involved genes in sorghum under drought stress.

Relationship between the amount and composition of epicuticular wax and tolerance of Ipomoea biotypes to glyphosate

Ipomoea species are troublesome weeds in crop systems through Brazil. Drought stress typically reduces glyphosate efficacy by reducing the foliar uptake of herbicides and their translocation. Using both glyphosate tolerant (GT) and sensitive (GS) plants from Ipomoea grandifolia, I. indivisa and I. purpurea species, this research aimed to (a) correlate amounts of epicuticular wax and tolerance to glyphosate in plants and (b) determine the effect of drought stress (DStress) on changes in the quantity and chemical composition of plant epicuticular waxes. The dose that causes 50% inhibition of growth (GR50) of the biotypes varied between 62 and 1208 (I. grandifolia), 159 and 913 (I. indivisa), and 389 and 1925 g a.e. ha−1 of glyphosate (I. purpurea). There was low inverse correlation (–0.46) between the amount of epicuticular wax and the sensitivity to glyphosate. GT biotypes of the species presented greater plastic capacities than GS biotypes for increasing the amount of epicuticular wax under DStress. The three Ipomoea species exhibited different chemical profiles of waxes supported by IR spectra, which allows for their differentiation. For I. grandifolia and I. purpurea, there was an increase in the polar components in the state without DStress, while for the species I. indivisa, no differences in infrared spectra were detected between the two water conditions.

Relative Humidity Influences Epicuticular Wax Load and Particulate Matter Accumulation on the Leaf Surface in <i>Asplenium nidus</i>

Particulate matter (PM) has recently been considered one of the most harmful air pollutants to public health. Plants have been known to degrade and deposit particle pollutants with epicuticular wax (EW), and this capacity can be influenced by environmental conditions including relative humidity (RH). The present study examined the effects of RH on EW generation and PM deposition upon leaf surfaces within Asplenium nidus ‘Avis’. The plants were treated in growth chambers with two levels of RH (low: 30% - 40% and high: 80% - 90%) for a period of four weeks, and subsequently exposed to a 30 μg･m-3 concentration of TiO2 particles as a PM resource for 72 hours. The EW ultrastructure on the leaf surface was observed as the thin films type, which was not morphologically changed in the condition of low or high RH treatment. For four weeks of RH treatment, the fresh weight and leaf area per plant were not significant between low and high RH treatment, while dry weight was significantly higher in the high RH condition. We also found that greater amounts of EW per fresh weight, dry weight and leaf area were generated in high RH. However, the total amounts of PM deposition (surface PM + in-wax PM) of the plants were higher within the low RH treatment with a higher proportion of surface PM. In contrast the proportion of in-wax PM was 15% higher within the high RH. These results suggest that EW generation is affected by air humidity and that proportion of PM deposition in the EW layer were influenced by the amount of total wax load.

Modification of the epicuticular waxes of plant leaves due to increased sunlight intensity

Climatic changes observed around the world in recent years are associated with an increase in the solar radiation intensity and temperature and reduction in the humidity. Fluctuations of environmental factors significantly change the conditions for the existence of plants, which dictates the need for adaptive reactions of plant organisms at the different levels of their organization. Such dangerous processes as excessive heating of the surface of plant leaves and water loss can be prevented by the formation of a cuticle, which is a complex composition consisting of cutin and the soluble intracuticular and epicuticular waxes. We suggested that the structure, component composition and properties of the cuticle of trees undergo adaptive changes due to microclimatic conditions in different parts of the tree crown. The study was aimed at the identification and evaluation of light-induced differences in the accumulation and composition of leaf epicuticular waxes of Ulmus trees (native U. minor Mill. and alien U. pumila L.), and was conducted in 2018–2019 in Dnipro city located in the steppe zone of Ukraine. Analysis of the waxes’ chloroform extracts was carried out using GC Shimadzu 2010 PLUS equipped with a flame ionization detector and capillary column SP-2560. The highest amount of epicuticular waxes (12.23 ± 0.39 µg/cm2) was on the sunlit leaves of U. pumila, and wax deposits on the sunned leaves exceeded twice those on the shaded leaves in both U. minor and U. pumila. Long-chain hydrocarbons detected in the epicuticular waxes of both elm species were represented by free fatty acids, aldehydes, alcohols, and n-alkanes in various ratios. In the epicuticular waxes of U. minor, fatty acids dominated both on shaded and sunned leaves, while alkanes together with alcohols were the main components in U. pumila waxes, especially on the sunlit leaves. According to our results, local high illumination of leaves in the crown of both elm species caused increase in share of long-chain alkanes (1.2–1.9 times), but simultaneous reduction of the content of free fatty acids (1.5–16.8 times) in the epicuticular waxes’ composition. General patterns of the leaf epicuticular waxes’ modification due to increased solar radiation and air temperature can indicate the adaptive metabolic responses of woody plants to changing climatic conditions.

Amounts and Types of Epicuticular Leaf Waxes among Onion Accessions Selected for Reduced Damage by Onion Thrips

Onion thrips (Thrips tabaci) is the main insect pest of onion (Allium cepa), and feeding damage routinely causes serious yield losses. Lower amounts of epicuticular waxes on onion leaves have been associated with fewer onion thrips and less feeding damage, and research is needed to assess the relationships between amounts and composition of epicuticular waxes and feeding damage by onion thrips. This study used gas chromatography mass spectroscopy to determine amounts and types of epicuticular waxes on the foliage of onion accessions that had been field-selected for lower damage from onion thrips. Hentriacontanone-16 (H16), octaconasol-1, and triacontanol-1 were the most prevalent waxes on the foliage of these selections. Amounts of H16 were significantly lower on selections visually classified as having glossy or semiglossy foliage. Semiglossy selections were identified with similar amounts of total epicuticular wax as waxy phenotypes, due primarily to lower amounts of H16 and higher amounts of other waxes. These semiglossy selections suffered significantly less feeding damage from onion thrips in a field evaluation, supporting the identification of unique wax profiles toward the development of thrips-resistant onion.

Genetic Analyses of Epicuticular Waxes Associated with the Glossy Foliage of ‘White Persian’ Onion

Onion (Allium cepa) plants with lower amounts of epicuticular waxes on foliage suffer less damage from the insect pest Thrips tabaci (onion thrips). Glossy onion accumulates significantly less epicuticular wax compared with wild-type “waxy” onion, and a single recessive locus (gl) has been proposed to condition this phenotype. Genetic analyses of types and amounts of epicuticular waxes were completed using two segregating families from the cross of the glossy inbreds B9885 and B9897 (both originally selected from the onion cultivar White Persian) with waxy inbred B8667 and semiglossy (intermediate amounts of waxes) inbred B5351, respectively. F2 progenies were grown in greenhouses and scored visually for foliar phenotypes, and amounts and types of epicuticular waxes were determined using gas chromatography-mass spectrometry (GCMS). For one F2 family from the cross of glossy B9885 by waxy B8667, visually scored glossy vs. waxy foliage fit a 1:3 ratio and the phenotype mapped to chromosome 8 of onion. This same region on chromosome 8 was significantly associated with amounts of the ketone hentriacontanone-16 (H16) and fatty alcohols 1-octacosanol (Oct1) and 1-triacontanol (Tri1). Visually scored F2 progeny from the cross of glossy B9897 × semiglossy B5351 did not fit expected models for one or two recessive loci. Significant quantitative trait loci (QTL) were revealed on chromosomes 5 and 8 controlling amounts of H16. Epistasis was detected between regions on chromosomes 1 and 8, and a 100-fold increase of H16 was conditioned by homozygous genotypes for the B5351 region on chromosome 1 and the B9885 region on chromosome 8. The three QTL model explained 41% of the phenotypic variation for amounts of H16 at logarithm of odds of 16.6. Amounts of Oct1 and Tri1 in the B9897 × B5351 family were associated with a major QTL on chromosome 1, explaining 37% to 46% of the phenotypic variation, respectively. This research demonstrates that glossy foliage of ‘White Persian’ onion is conditioned by a recessive locus on chromosome 8 for which we propose the name glwp. These results are important for selection of onion with unique profiles of epicuticular waxes to reduce losses resulting from onion thrips.

Epicuticular wax analysis of wild and agronomically important Agave species

Agaves are cultivated in Mexico as a source of industrial products such as fibers, nutritional supplements and alcoholic beverages. A particularly important trait present in all agaves, which makes them economically viable crops for certain geographic regions, is their ability to grow under water limiting conditions. One of the anatomical characteristics that contributes to this adaptation, is the thick layer of epicuticular waxes deposited on their surface which reduces water loss by evapotranspiration. Still, to date, and in spite of their economic importance, there has been practically no effort to improve the genetics and productivity of agaves; this investigation focuses on the differences in the content and types of the epicuticular waxes present on the surface of leaves of wild and agronomically important Agave species with different ploidy level. The agaves analyzed were two diploids [A. tequilana Weber and the hybrid H11648 (A. amaniensis Trel. & Nowell x A. angustifolia Haw. back crossed to A. amaniensis)]; two pentaploids (A. fourcroydes var. Sac ki and A. fourcroydes var. Yaax ki) and a hexaploid (A. angustifolia var. Chelem ki)The epicuticular waxes were obtained by hexane extraction and their chemical composition was established by capillary gas chromatography–mass spectrometry (GC/MS). The amount of epicuticular wax varied significantly between the different types (4.40–35.63 μg cm−2), with A. angustifolia var. Chelem Ki (hexaploid) and A. tequilana (diploid) presenting the highest and lowest amounts, respectively. With the exception of A. tequilana, n-alkanes were the main components (63.32–92.13 % of total wax) in the epicuticular wax, with hentriacontane (C31) and tritriacontane (C33) as main compounds. Alternatively, in A. tequilana two aliphatic alcohols were the main components of the wax. These results suggest a correlation between the total epicuticular wax content, the chemical composition of the wax, the ploidy level and the type of habitat in which they grow. This information contributes to the understanding of the tolerance of agaves to different types of stress.

Mode of Inheritance and Combining ability studies on Epicuticular wax Production in Resistance to Black pod disease in Cacao (Theobroma cacao L.)

Abstract Black pod caused by Phytophthora species is a devastating disease of cacao (Theobroma cacao L.) in production regions worldwide. Breeding for cacao genotypes resistant to black pod disease is crucial for sustainable cocoa production and profitability. Although breeding programmes in the past have made considerable efforts in improving resistance of cocoa genotypes with diverse genetic background, the disease continues to cause unacceptable yield losses in cacao production. To understand the mode of inheritance of epicuticular wax on the surface of cocoa pod known to play a major role in resistance to black pod disease, a 6 × 6 full diallel and a M x N (6 × 4) mating designs were used and data was analysed using Griffing’s method I model I approach and the North Carolina design –II approach, respectively. The results of the two mating designs were consistent and showed that epicuticular wax on leaf and pod surfaces of cacao were under the control of additive genetic effects. The non-additive effects were generally much smaller compared to the additive genetic effects. The significant association between GCA estimates of parents and their means indicates that parental values could be used as indicators of progeny performance. The best general combiners for epicuticular wax load on leaf and pod surfaces were Pa7/808, T60/887 and Pa 150. The larger additive components and heritability observed in this study, indicates that pedigree selection could be used to develop cacao cultivars with high amount of epicuticular wax on pod surface to enhance resistance to black pod disease.

Ex vitro rooting using a mini growth chamber increases root induction and accelerates acclimatization of Kopyor coconut (Cocos nucifera L.) embryo culture-derived seedlings

Ex vitro rooting using a mini growth chamber to maintain relative humidity has been used to mass produce true-to-type Kopyor coconut (Cocos nucifera L.) seedlings through embryo culture. This new process was found to (1) improve the proportion of seedlings successfully transferred to soil (from 40 to 90% for seedlings with roots); (2) achieve this step in the shortest time possible (a reduction from 10 to 4 mo in in vitro culture); (3) improve root formation using indolebutyric acid (IBA; an improvement in the number of primary roots from 2 to 5); and (4) improve the vigor of seedlings ex vitro (improvements of fresh weight, shoot length, number of opened leaves, leaf thickness, amount of epicuticular wax, and stomatal density). The best ex vitro rooting and rapid acclimatization protocol was obtained when 4-mo-old seedlings with two opened leaves were kept in the mini growth chamber for 3 mo before being transferred into soil, and when the mini growth chamber was flooded with a quarter strength hybrid embryo culture (HEC) medium with 1 μM IBA but depleted of vitamins and sugar. This protocol was efficient in delivering high-value Kopyor seedlings to the field (90% success rate), with a decreased risk of contamination and lower labor cost. The improved process was found applicable to both tall and dwarf Kopyor and other coconut types.

Evaluating Iris Yellow Spot Disease Incidence and Severity in Onion Germplasm of Varying Leaf Characteristics

Iris yellow spot (IYS) disease, caused by Iris yellow spot virus (IYSV), results in irregular and diamond-shaped, chlorotic, and necrotic lesions on the leaves and seedstalks of onions (Allium cepa L.). These lesions reduce leaf photosynthetic area and ultimately reduce onion bulb size and yield from larger bulb classes. IYSV is vectored by onion thrips (Thrips tabaci L.) that are difficult to control under certain environmental conditions. Currently, no onion cultivar is resistant to the disease symptoms, virus, and/or thrips. Twenty-one cultivars and 17 germplasm lines were evaluated in the field for IYS disease severity and thrips densities at multiple times during the season as well as leaf color, waxiness, and axil openness of these entries. Plants were grown under conditions that favored thrips populations (high temperatures, low moisture, and no insecticidal spray applications), IYSV presence and distribution, and IYS development. Plants of New Mexico State University (NMSU) 07-10-1 had fewer thrips than several entries later in the season in both 2009 and 2010. Several entries exhibited a lower number of thrips per plant early or later in the season; however, these results were not consistent across years and were not associated with a particular foliage characteristic. Lighter leaf color and/or a lesser amount of epicuticular wax did not always result in the fewest number of thrips per plant as has been reported in the literature. Plants of NMSU 09-58 tended to exhibit fewer and less severe IYS symptoms early in the season as compared with plants of other entries.

Relationship between Leaf Surface Characteristics and Particle Capturing Capacities of Different Tree Species in Beijing

Leaf surface is a multifunctional interface between a plant and its environment, which affects both ecological and biological processes. Leaf surface topography directly affects microhabitat availability and ability for deposition. In this study, atomic force microscopy (AFM) and the resuspended particulate matter method were applied to evaluate the adsorptive capacity of the leaf surface. Patterns of particulate‐capturing capacities in different tree species and the effect of leaf surface features on these capacities were explored. Results indicated the following: (1) more total suspended particles (TSP) per unit leaf area were captured by coniferous tree species than by broad‐leaved tree species in a particular order—i.e., Pinus tabuliformis > Pinus bungeana > Salix matsudana > Acer truncatum > Ginkgo biloba > Populus tomentosa; (2) Significant seasonal variation in particulate‐capturing capacities were determined. During the observation period, the broad‐leaved tree species capturing TSP and coarse particulate matter (PM10) clearly exhibited a ∩‐shape pattern— that is, increasing initially and later on decreasing; meanwhile, the ∩‐shape pattern was not clearly shown in P. tabuliformis and P. bungeana. However, no obvious patterns in the absorption of fine particulate matter (PM2.5) were found in the tested tree species; (3) The leaf surface topography, as observed by AFM and scanning electron microscopy, revealed that the broad‐leaved tree exhibits a good correlation between micro‐roughness of leaf surfaces and density of particles settling on leaf surfaces over time. However, the main factors affecting the adsorptive capacities of the leaves in coniferous trees are the number of stomata as well as the amount of epicuticular wax and the properties of the cuticle in different seasons.

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

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.

Preliminary Study of the Characteristics of Several Glossy Cabbage (Brassica oleracea var. capitata L.) Mutants

To determine the characteristics and potential practical applications of glossy cabbage (Brassica oleracea var. capitata L.) mutants, five different glossy mutants were studied. The amount of epicuticular wax covering the mutant leaves was only approximately 30% that of the wild-type (WT) leaves. The wax crystals of WT plants were columnar and linear, while they were granular and rod-shaped in the mutants. Additionally, in WT cabbage, the primary wax components were alkanes, alcohols, fatty acids, ketones, and aldehydes. There was a significant decrease in the abundance of alkanes and ketones in the wax of the mutants. The glossy-green trait of the mutants may be the result of an inhibited alkane-forming pathway. Higher rates of chlorophyll leaching and water loss demonstrate that the mutant leaves were more permeable and sensitive to drought stress than the WT leaves. Growth curve results indicated that the growth rate of mutant-1 and mutant-3 was slower than that of the corresponding WT cabbage, resulting in shorter plants. However, the growth rate of mutant-2 was not influenced by the lack of coating wax. An investigation of the agronomic traits and heterosis of the glossy cabbage mutants indicated that all five mutants had glossy-green leaves, which was a favorable characteristic. The F1 plants derived from crosses involving mutant-2 exhibited obvious heterosis, suggesting the observed glossy-green trait is controlled by a dominant gene. Therefore, mutant-2 may be useful as a source of genetic material for future cabbage breeding experiments.

<b>Morphological and chemical characteristics of onion plants (<i>Allium cepa</i> L.) associated with resistance to onion thrips

Thrips tabaci Lindeman is the main pest of onion crops, and chemical control is the main method adopted by farmers. Alternative control methods should be prioritised to reduce the amount of insecticides used. Resistant cultivars are one efficient way to control thrips in the field. Our aim was to assess the influence of morphological and chemical characteristics of seven onion cultivars and their resistance to T. tabaci. The number of thrips and the morphological and chemical characteristics of the plants were assessed. Among the evaluated cultivars, Alfa São Francisco RT, BR 29 and Sirius showed resistance to T. tabaci, as indicated by the lower number of thrips observed during the cycle (64, 87, and 74 thrips, respectively). Morphological and chemical characteristics were associated with onion’s resistance to T. tabaci. For the cultivar Alfa São Francisco RT, a wider central angle (16.4°), a thinner cuticle, a larger amount of epicuticular waxes, and stomata on the surface of leaves accounted for resistance. For the cultivars BR 29 and Sirius, the resistance was likely due to the presence of resistance-conferring substances or high amounts of some component in the chemical composition of plants.