Leaf Epicuticular Wax Research Articles

First line of defence: Eucalyptus leaf waxes influence infection by an aggressive fungal leaf pathogen.

Leaf epicuticular waxes provide important anatomical and chemical defences against fungi that infect leaves. In this study we analysed the leaf wax composition of Eucalyptus grandis × Eucalyptus urophylla hybrids with contrasting susceptibilities to Teratosphaeria leaf blight (TLB) caused by Teratosphaeria destructans, one of the most important foliar diseases of Eucalyptus. The Eucalyptus cuticular wax was extracted from non-inoculated and inoculated genotypes with different levels of susceptibility to TLB and analysed by gas chromatography-mass spectrometry. The results showed that a triterpenoid, cycloartenol (CAS), was abundant in a resistant genotype and that hexanedioic acid content increased in the resistant genotypes in response to T. destructans infection. In contrast, palmitic acid was significantly more abundant in the inoculated highly susceptible genotype. In-vitro and in-planta T.destructans spore germination assays with pure compounds, showed that CAS and hexanedioic acid significantly inhibited spore germination. Application of these two compounds to the leaves of a susceptible host also significantly increased resistance to infection. In contrast, palmitic acid promoted spore germination and, when applied to the leaves of a resistant genotype, increased colonization by the pathogen. This is the first study providing insights into differences in the leaf wax composition of hosts with different levels of susceptibility to T. destructans. It also showed that leaf wax compounds can modulate spore germination and, ultimately, host resistance to infection.

An increased wax load on the leaves of goji plants (Lycium barbarum) results in increased resistance to powdery mildew

Abstract Background Goji (Lycium barbarum) is an important economic crop that is widely cultivated in Northwest China and is known as superfood. Goji plants are often affected by powdery mildew (Arthrocladiella mougeotii) in the field, resulting in considerable reduction in production and serious economic losses. The long-term reliance on agricultural chemicals to control powdery mildew not only leads to environmental pollution, but also causes excessive residues to accumulate in fruits, endangering human health. The plant epicuticular wax is the first physical barrier between land plants and the atmospheric environment, and plays an important role in the interactions of plants with pathogenic microorganisms. However, the relationship between epicuticular wax and powdery mildew resistance in goji plants is not well understood. Results The leaf epicuticular wax crystals of ‘Ningqi I’ goji were dense and small, and the wax load was 121.74 μg/cm2, which was 3.36 times greater than that of ‘Huangguo’ goji. The ratio of alcohol components in ‘Ningqi I’ goji was 121.18% greater than that in ‘Huangguo’ goji. The incidence rate and disease index of ‘Ningqi I’ goji inoculated with powdery mildew were significantly lower than those inoculated ‘Huangguo’ goji, showing high resistance and moderate susceptibility, respectively. After mechanical wax removal, the disease indices of the two goji varieties increased significantly, indicating extreme susceptibility. Seventeen differential expression genes showing significantly greater expression in ‘Ningqi’ goji leaves than in ‘Huangguo’ goji leaves were enriched in genes involved in fatty acid elongation and the wax biosynthesis pathway. The FAR activity and relative expression levels of LbaFAR and LbaWSD1 in ‘Ningqi I’ goji were significantly greater than those in ‘Huangguo’ goji. The relative expression levels of these genes significantly increased in the overexpression tobacco lines FAR-OE and WSD1-OE, and the wax load were augmented by 46.10% and 22.23%, respectively. Conclusions The increased expression of the LbaFAR and LbaWSD1 genes in ‘Ningqi I’ leaves led to increased FAR and WSD1 activity, increasing the wax load and alcohol content of the epicuticular of leaves, and improving leaf glossiness, resulting in strengthened resistance to powdery mildew. Therefore, the production of leaf epicuticular wax mediated by the LbaFAR and LbaWSD1 genes could be the main reason for the difference in powdery mildew resistance between the two goji varieties, which can provide a theoretical basis for the selection of resistant varieties to control goji powdery mildew. Graphical Abstract

Effects of sodium silicate on the growth and starch content in seeds of Mungbean (Vigna radiate L.) under salt stress

Mungbean is known as an essential legume with high nutritional value for human beings. They are not only a source of vegetable proteins but they are also rich in vitamins and minerals. Salinity stress affects negatively mungbean growth, especially at germination and seedling stages. Thus, finding measures to limit the impact of salinity stress will have positive effects on mungbean production. The present study investigates the effectiveness of sodium silicate application (6, 12, 18, 24 mM) in alleviating the negative impact of salinity stress on seed germination and seedling growth. Physiological and biochemical changes during the growth of mungbean were analyzed. Our experiments showed that salinity stress dramatically impeded the germination of mungbean seeds. Under the salinity condition (125 mM NaCl), the germination index decreased by approximately 65 % compared to control plants. Salinity stress caused a significant decrease in leaf chlorophyll and leaf relative water content, whereas respiration rate, leaf epicuticular wax and carotenoid content increased in comparison to control plants. The application of 12 mM sodium silicate improved plant performances under salinity stress, as indicated by the increase in fruit and seed number, seed weight (72.33 mg), and starch content (0.51 g g−1) in seeds. Moreover, sodium silicate treatment induced an increase in chlorophyll a content (4.00 mg g−1), carotenoid content (2.50 mg g−1), and epicuticular wax content (3.67 µg cm−2) in the leaves of plants under salt stress. These results were scientific evidence that might help us to understand the role of Si in the improvement of the salt tolerance of mungbean.

Leaf epicuticular wax as a determinant trait for drought resistance in cereals

The wax coating is an element of the lipid protective layer, the cuticle, which covers the above-ground organs of plants and is the main barrier that prevents non-stomatal water loss. The cuticle helps protect plant surfaces from pathogens and ultraviolet radiation and influences interactions between plants and insects. The accumulation of cuticular wax is one of the mechanisms of adaptation to drought stress. As a result, there are more and more reports on the relationship between cuticular wax and plant resistance to drought. This article deals with the relationship between cuticular waxes and drought resistance in cereals. The paper presents the achievements to date on (i) the relationship between wax biosynthesis and plant response to drought stress using glaucous and nonglaucous near-isogenic lines and on (ii) investigating the role of genes for cuticular wax biosynthesis and transport and the transcription factors that regulate them using mutants with disrupted wax coat formation.

A Method for Epicuticular Wax and Contaminant Removal from Herbarium Specimens for Scanning Electron Microscopy

Abstract We describe a method for cleaning leaf epicuticular wax and contaminants from herbarium specimens in preparation for scanning electron microscopy. Specimens are rinsed in chloroform, heated at 50°C for 8 hrs, ultrasonicated in 70% ethanol, and subjected to critical-point drying. This method helps preserve and reveal the surface details of specimens that are heavily covered with epicuticular wax and contaminants, making many morphologically and functionally important details readily visible. We tested our method by using it to clean herbarium specimens and comparing the results with those obtained using three other chemicals: acetone, xylene, and 1:1 acetone:xylene, confirming that chloroform treatment was the most effective.

Relationship between the amount of black carbon particles deposited on the leaf surface and leaf surface traits in nine urban greening tree species

To select urban greening tree species suitable for the purification of the atmosphere polluted by black carbon (BC) particles, it is necessary to clarify the determinants of the amount of BC particles deposited on the tree leaves. In the present study, we investigated the relationship between the amount of BC particles that were deposited from the atmosphere and firmly adhered to the leaf epicuticular wax, and leaf surface traits in seedlings of nine tree species grown for two years under natural conditions (Fuchu, Tokyo, Japan). There was a significant interspecific difference in the maximum amount of BC particles deposited on the leaf surface, and the order was as follows: Ilex rotunda > Cornus florida > Osmanthus fragrans > Cornus kousa > Quercus glauca ≒ Quercus myrsinifolia > Magnolia kobus ≒ Zelkova serrata ≒ Styrax japonicus. In the nine tree species, significant highly positive correlations were observed between the amount of BC particles deposited on the leaf surface, and the hydrophobicity of leaf epicuticular wax determined by its chemical composition. Therefore, we concluded that the hydrophobicity of leaf epicuticular wax is an important determinant of the amount of BC particles deposited on the leaf surface of urban greening tree species.

Laguncularia racemosa leaves indicate the presence of potentially toxic elements in mangroves

Brazilian mangroves have been severely impacted by metallurgical, petrochemical, pyrometallurgical smelters and other industrial activities. In Rio de Janeiro, mangroves are part of the Atlantic Rainforest now under the stress of high levels of industrial waste. Therefore, this work aimed to detect potentially toxic elements (PTEs) by evaluating the leaves of Laguncularia racemosa (L.) Gaertn. f. collected from three mangroves with different levels of pollution. To gain further insight toward an accurate diagnosis of the effects of anthropogenic pollution on mangrove stands, we evaluated leaf epicuticular wax composition, as well as morphological and anatomical traits. Samples were analyzed using inductively coupled plasma-optical emission spectroscopy (ICP-OES), gas chromatography (GC) and microscopy. Results revealed variation in the contents of PTEs among the three mangroves from lowest to highest concentration, as follows: Al (0.30–0.73), Pb (0.095–0.325) and Zn (0.25–0.30) mg/kg. Zn was detected in sclerenchyma tissues. Leaf epicuticular wax contained more than 50% of triterpenes, in particular, the pentacyclic triterpenes lupeol (41.61–55.63%) and β-amyrin (8.81–16.35%). Such high concentrations promote the increase in leaf permeability to salts and PTEs. Micromorphology of leaf epicuticular wax in L. racemosa also varied among the three evaluated sites, especially around stomatal openings, but no harmful changes were noted. L. racemosa plays a key role in the rich diversity of mangrove ecosystems. As such, this species could, by the presence of PTEs in its leaves, be a suitable biomonitor of toxic substances in coastal environments of the world and used accordingly in strategies designed for eco-sustainable technologies.

Compositional variances in cuticular lipids of wild and domesticated barley leaves and their impact on plant-environment interactions

One of the oldest cereal crops, barley is thought to have been domesticated ∼ 8000 years ago, in the Fertile Crescent. In this study, we explored the overlooked contribution of cuticular lipid metabolism to barley domestication by comparatively characterizing wild and domesticated barley variants. We revealed substantial phenotypic variances in plants’ overall morphology and in vegetative and reproductive tissues. Multiple microscopic approaches combined with gas chromatography-mass spectrometry (GC-MS) metabolite profiling indicated that wild barley leaves are more densely covered with epicuticular waxes compared to domesticated leaves with distinct compositions, but both variants contain a similar cuticle ultrastructure. Gene expression assays corroborated these observations showing higher transcript expression of key epicuticular wax biosynthetic genes in wild barley leaves, but similar expression patterns of cutin biosynthetic genes in leaves of both cultivars. Wild barley leaves also transpired water at higher rates apparently due to higher stomata density and conductance. Previous evidence claimed that barley leaf epicuticular waxes shape the interactions with Blumeria graminis f.sp. hordei (Bgh), the causal agent of powdery mildew in barely. However, in-vivo and in-vitro inoculation assays inferred that the disparate wax content and composition in wild and domesticated leaves had no apparent effect on Bgh pre-penetration processes. Altogether, our data provide novel insight into the compositional variances in cuticular lipids of wild and domesticated barley leaves and their impact on plant-environment interactions.

Relationship between Leaf Traits and PM-Capturing Capacity of Major Urban-Greening Species

High concentrations of airborne particulate matter (PM) in urban areas are of great concern to human health. Urban greening has been shown to be an effective and eco-friendly way to alleviate particle pollution, and attention to its role in mitigating particle pollution has increased worldwide. The species-specific PM-capturing capacity of ten urban-greening species in Seoul was evaluated by leaf functional traits (average leaf area (ALA), specific leaf area (SLA), and leaf width-to-length ratio (W/L)), microstructures (roughness, stomata, and trichomes), and physicochemical traits (contact angle (θw), surface free energy (rs), the work of adhesion for water (Wa), and epicuticular wax loads (EWL)). The relationships between leaf traits and PM adsorption by leaves were revealed by Pearson’s correlations and principal component analysis (PCA). A gravimetric method was used to quantify, by particle size, the PM adsorbed on leaf surfaces or embedded in leaf epicuticular wax layers. The key factors for PM adsorption on leaf surfaces were the SLA, the mean roughness value (Ra), and stomatal size. The SLA and Ra of adaxial leaf surfaces were negatively correlated with PM accumulation on leaf surfaces, while stomatal length and width were positively correlated with surface PM load. The rs and EWL positively affected the in-wax PM load. Species-specific PM deposition was the result of complicated mechanisms of various leaf traits. Three evergreen shrub species, Buxus sinica (Rehder & E.H. Wilson) M.Cheng var. insularis (Nakai) M.Cheng, Taxus cuspidata Siebold & Zucc., and Euonymus japonicus Thunb., were efficient in capturing both surface PM and in-wax PM. The PCA revealed that the high PM accumulation efficiency of these three species might be attributable to the interaction between stomatal size and EWL. Aesculus turbinata Blume, Chionanthus retusus Lindl. & Paxton, and Rhododendron schlippenbachii Maxim. had intermediate PM adsorption ability, which might be a result of interactions among stomatal density, the Wa of adaxial surfaces, and ALA. Magnolia denudata Desr., Styphnolobium japonicum (L.) Schott, Liriodendron tulipifera L., and Ginkgo biloba L. had low PM accumulation efficiency. These four species exhibited correlations among SLA, the Ra of adaxial leaf surfaces, and W/L, which had negative effects on PM adsorption.

Plant defense to herbivore: role of leaf epicuticular wax composition of citrus cultivars in citrus leafminer, Phyllocnistis citrella Stainton (Lepidoptera: Gracillariidae) larval density

Aiming to assess the role of leaf waxy cuticle and its chemical composition on citrus leafminer, Phyllocnistis citrella (Lepidoptera: Gracillariidae) larval feeding, six citrus cultivars were selected. Our findings showed that the larval density was higher at 59.5% on Mayer lime followed by 53.6% on Kinnow and the least activity of CLM was found (19.3-38.4%) on Musambi. The cuticular wax layer was found greater (67.6 µg/cm2) in Tangerine (Fairchild) followed by 59.6 µg/cm2 in Succari and 56.0 µg/cm2 in Musambi. The results showed that the epicuticular wax layer had negative and significant (P < 0.05) relation with the larval density. Other chemical compounds; aldehyde, alcohol, fatty acid, and hydrocarbon showed non-significant relation with the CLM larval density. Multiple regression analysis showed a 33.5% role of epicuticular wax with CLM larval density. The cultivars such as Succari and Musambi with a greater amount of leaf wax showed a lower density of CLM larvae. The study provides important information on wax related compounds involved in citrus-CLM interaction, which can help in developing an efficient control strategy for this destructive pest.

A double-edged effect of manganese-doped graphene quantum dots on salt-stressed Capsicum annuum L.

The objective of the current study is to evaluate both the positive and negative effects of manganese-doped graphene quantum dots (GQD-Mn) on Capsicum annuum L. grown under salt stress. GQD-Mn was synthesized, characterized, and foliar-applied (250 mg/L, 120 mg/L, 60 mg/L) to C. annuum L. before and after the flowering stage, during which 100 mM of NaCl solution was introduced into the soil as salt stress. Controls were designed as absolute control (no nanomaterials or salt) and negative control (no nanomaterials only salt). Herein, we report that GQD-Mn offset the reduction of fruit production in salt-stressed C. annuum L. by around 40 %. However, based on a comprehensive analysis of normal alkanes (n-alkane) using gas chromatography–mass spectrometry (GC–MS), we also observed that the leaf epicuticular wax profile was disturbed by GQD-Mn, as the concentration of long-chain n-alkanes was increased. Meanwhile, the content of magnesium (Mg) and zinc (Zn) indicated a potential promoted photosynthesis activity in C. annuum L leaves. We hypothesize that the optical properties of GQD-Mn allow leaves to utilize light more efficiently, thus improving photosynthetic activities in plants to acclimate salt stress. But the increased light usage also induced heat stress on the leaf surfaces, which caused n-alkanes changes. Our results provided a unique perspective on nano-plant interaction that value both beneficial and toxic effects of nanomaterials, especially when evaluating the safety of nano-enabled agriculture in areas facing harsh environmental conditions such as salinity.

Erratum to: Mapping the genetic loci regulating leaf epicuticular wax, canopy temperature, and drought susceptibility index in Triticum aestivum

Erratum to: Mapping the genetic loci regulating leaf epicuticular wax, canopy temperature, and drought susceptibility index in <i>Triticum aestivum</i>

Correlation between leaf epicuticular wax composition and structure, physio-biochemical traits and drought resistance in glaucous and non-glaucous near-isogenic lines of rye.

SUMMARYThe objective of this research was to investigate the differences between glaucous and non‐glaucous near‐isogenic lines (NILs) of winter rye (Secale cereale L.) in terms of epicuticular wax layer properties (weight, composition, and crystal morphology), selected physiological and biochemical responses, yield components, above‐ground biomass, and plant height under soil drought stress. An important aspect of this analysis was to examine the correlation between the above characteristics. Two different NIL pairs were tested, each consisting of a typical glaucous line and a non‐glaucous line with a recessive mutation. The drought experiment was conducted twice (2015–2016). Our study showed that wax accumulation during drought was not correlated with higher leaf hydration and glaucousness. Environmental factors had a large impact on the response of the lines to drought in individual years, both in terms of physiological and biochemical reactions, and the composition of epicuticular leaf wax. The analysed pairs displayed significantly different responses to drought. Demonstration of the correlation between the components of rye leaf wax and the physiological and biochemical parameters of rye NILs is a significant achievement of this work. Interestingly, the study showed a correlation between the wax components and the content of photosynthetic pigments and tocopherols, whose biosynthesis, similarly to the biosynthesis of wax precursors, is mainly located in chloroplasts. This suggests a relationship between wax biosynthesis and plant response to various environmental conditions and drought stress.

Transcriptome and physiological analyses provide insights into the leaf epicuticular wax accumulation mechanism in yellowhorn

Plantations and production of yellowhorn, one of the most important woody oil and urban greening trees widely cultivated in northern China, have gradually become limited by drought stress. The epicuticular wax layer plays a key role in the protection of yellowhorn trees from drought and other stresses. However, there is no research on the mechanism of wax loading in yellowhorn trees. In this study, we investigated the anatomical and physiological characteristics of leaves from different germplasm resources and different parts of the same tree and compared their cuticle properties. In addition, the different expression patterns of genes involved in wax accumulation were analyzed, and a coexpression network was built based on transcriptome sequencing data. Morphological and physiological comparisons found that the sun leaves from the outer part of the crown had thicker epicuticular wax, which altered the permeability and improved the drought resistance of leaves, than did shade leaves. Based on transcriptome data, a total of 3008 and 1324 differentially expressed genes (DEGs) were identified between the sun leaves and shade leaves in glossy- and non-glossy-type germplasm resources, respectively. We identified 138 DEGs involved in wax biosynthesis and transport, including structural genes (such as LACS8, ECH1, and ns-LTP) and transcription factors (such as MYB, WRKY, and bHLH transcription factor family proteins). The coexpression network showed a strong correlation between these DEGs. The differences in gene expression patterns between G- and NG-type germplasm resources under different light conditions were very clear. These results not only provide a theoretical basis for screening and developing drought-resistant yellowhorn germplasm resources but also provide a data platform to reveal the wax accumulation process of yellowhorn leaves.

Mapping the genetic loci regulating leaf epicuticular wax, canopy temperature, and drought susceptibility index in Triticum aestivum

AbstractEarlier studies have shown the significant impact of leaf glaucousness and cooler canopies on wheat (Triticum aestivum L.) yield. However, breeding for drought adaptive traits and potential yield as responses to heat or water deficit were poor. The genetic basis for drought‐adaptive traits and yield potential were assessed using quantitative trait locus (QTL) analysis. The 180 recombinant inbred lines (RILs) were derived from a cross between ‘Len’ (USA) and ‘Halberd’ (Australian) wheat lines. The RIL population and the parents were genotyped with a 90K Infinium single nucleotide polymorphism (SNP) library to construct 22 linkage groups. The QTLs segregating for leaf epicuticular wax (EW), cooler canopies, drought susceptibility index (DSI), and grain attributes were identified in the population across five environments. The QTLs associated with leaf EW, cooler canopies, DSI–mean single head weight (MSHW), DSI–thousand‐kernel weight (TKW), and grain attributes co‐localized on chromosomes 1A, 2B, 3B, 6B, 7A, and 7B. Gene ontology of the leaf EW QTLs on chromosomes 2B and 3B indicated that their sequences were similar to an Arabidopsis ABC transporter gene, and the leaf EW QTL on chromosome 7B was similar to the sorghum [Sorghum bicolor (L.) Moench] ethylene‐insensitive gene. The favorable alleles associated with moisture stress tolerance were associated with the Halberd parent. The genetic loci (QWax.tam‐3B and QCTP.tam‐2B, QDSIM.tam‐2B.1) with higher logarithm of odds (LOD) and R² values could be important potential tools in breeding to improve. The chromosomal regions identified in this study can provide breeders with additional tools to develop drought‐ and heat‐tolerant cultivars through breeding.

Phthalates: environmental pollutants detected in leaf epicuticular wax of Avicennia schaueriana and Rhizophora mangle from a mangrove ecosystem

ABSTRACT This study aimed to investigate the accumulation of phthalates in the leaf epicuticular wax of Avicennia schaueriana and Rhizophora mangle. Leaves were collected from plants situated in three mangroves around Sepetiba Bay, Rio de Janeiro state, Brazil. Dibutyl phthalate (DBP) and di-n-octyl phthalate (DnOP) were detected in higher content in A. shaueriana leaf wax (44.26%) and in R. mangle leaves at 34.43%. A high incidence of plastic residue pollutants in leaf epicuticular wax of these two mangrove species most likely results from absorption from substrate, water or air.

Identification, Isolation and Characterization of GaCyPI Gene in Gossypium arboreum under Cotton Leaf Curl Virus Disease Stress

Pakistan is facing the threat of Cotton Leaf Curl Virus (CLCuV) which is transmitted through whitefly to cotton crop. Molecular mechanism of leaf epicuticular wax protects the plants from different pathogens including insect attack and disease transmission. Objective of current study is the isolation and characterization of a wax related gene GaCyPI from Gossypium arboreum under CLCuV infection. A fragment of 475 bp was isolated from the total RNA and 3’ and 5’ RACE-PCR products were arranged by overlapping the extended sequences at both the ends. Deduced protein sequence of GaCyPI showed homology with Cyclophilin cis-trans isomerase gene of Gossypium ramondii and Gossypium barbadanse. Multiple sequence alignment also revealed homology among the coding sequences of same gene. GaCyPI protein comprised of 173 amino acids and ORF finder revealed the 69 bases upstream at 5’ while 350 bp at 3’UTR. InterProScan revealed that it belongs to Cyclophilin-type peptidyl prolyl cis/trans isomerase (PPIase) family. Active sites are visible at specific amino acid positions and 3D structure was stable in Ramachandran plot. Prosa server showed protein residues have average 3D-1D score >= 0.2 and Z-Score was −6.74. Phylogenetic analysis revealed that G. raimondii is the closest species that shares the same sequence. Hence, GaCyPI has strong role in plants’ epicuticular wax and its genetic transformation may protect the cotton from whitefly which transmits CLCuV.

The Microbiota Dynamics of Alfalfa Silage During Ensiling and After Air Exposure, and the Metabolomics After Air Exposure Are Affected by Lactobacillus casei and Cellulase Addition.

Both inoculants treatment and enzyme treatment promote the reproduction of lactic acid bacteria (LAB) to produce enough lactic acid to lower pH in silage. The present study investigated the microbial community and metabolome in cellulase, Lactobacillus casei, and air treated alfalfa silage. Chopped and wilted alfalfa (first cutting, 29% dry matter) was ensiled without (CON) or with L. casei (1 × 106 cfu g–1 fresh matter) (LC) or cellulase (20,000IU, 0.5% of fresh matter) (CE) for 56 days, then exposed to air for 3 days (PO). Greater ensiling quality was observed in LC and CE, which had lower pH and higher lactic acid content than CON at 56 days of ensiling and 3 days post-oxygen exposure. Air exposure was associated with decreased lactic acid concentrations and increased yeast and mold counts in all silages. SEM showed that the structure of leaf epicuticular wax crystals were intact in fresh alfalfa, totally decomposed in CON silage, and partly preserved in CE and LC silage. Gas chromatography mass spectrometry revealed that 196 metabolites and 95 differential concentration were present in the 3 days air exposure samples. Most of these metabolites, mainly organic acids, polyols, ketones, aldehydes, are capable of antimicrobial activity. The bacterial communities were obviously different among groups and Lactobacillus developed to a dominant status in all silages. Lactobacillus became dominant in bacterial communities of LC and CE silages from days 7 to 56, and their relative abundances reached 94.17–83.93% at day 56, respectively. For CON silage, until day 56, Lactobacillus dominated the bacterial community with abundance of 75.10%. After 3 days of oxygen exposure, Lactobacillus and Enterococcus were predominant in CON, and Lactobacillus remained dominant in LC and CE silages. The results indicated that, compared to untreated silages, L. casei could be a priority inoculant for alfalfa silage to boost Lactobacillus abundance and improve fermentation quality. Our high-throughput sequencing and gas chromatography mass spectrometry results provide a deep insight into the bacterial community and metabolites in alfalfa silage.

Cuticular wax composition of mature leaves of species and hybrids of the genus Prunus differing in resistance to clasterosporium disease

The interaction of a host plant with pathogen implies an extremely complex process involving the outer waxy layer of the cuticle, cutin, cell membrane, and intracellular structures. However, the initial contact between plants and pathogens takes place in cuticular waxes covering the surface of leaves, stems and fruits. Despite many findings on the role of plant epicuticular waxes, there is a gap in the understanding of the relationship between individual compounds and their functions. The pathogenic fungus Clasterosporium carpohilum (Lev.) Aderh. parasitizes the tissues of many stone fruit trees, damaging leaf and fruit surface. The aim of this work was to find out if the quantity and composition of leaf epicuticular wax could be responsible for the resistance to clasterosporium disease. The study of differences of plants in fungal resistance was carried out on species and hybrids of the genus Prunus from the collection of the Botanical Garden of Oles Honchar Dnipro National University (Dnipro city, Ukraine). The chloroform extracts of epicuticular waxes from the surface of mature leaves were analyzed by gas chromatography connected to mass-spectrometry. GC/MS assay was performed using Shimadzu GCMS-QP 2020 El equipped with capillary column (5% diphenyl/95% dimethyl polysiloxane), and helium as a carrier gas. Mass Spectrum Library 2014 for GSMS was used to identify the separated compounds of the wax extracts. The maximum total wax amount on the adaxial and abaxial leaf surface of hybrid 2 was twice the minimum wax accumulation for hybrid 4. Overall, 20 individual compounds belonging to six hydrocarbon classes were identified. Leaf epicuticular wax composition both in Prunus persica (L.) Batsch and P. dulcis (Mill.) D. A. Webb, and hybrids was dominated by long-chain n-alkanes with even carbon number (77.6–90.9% of total sum). The alkenes’ class was represented only by 17-pentatriacontene detected in the wax of both Prunus species. Octadecanaldehyde was found in epicuticular wax of P. dulcis while absent in wax of the more resistant species P. persica. Prime alcohols 1-tetradecanol and 1-hexacosanol were detected in leaf waxes of hybrid 4 and P. dulcis respectively. The ester class contained seven compounds found in leaf epicuticular waxes of both plant species and all hybrid forms. The identification of phthalic acid esters in leaf wax extracts was unexpected, and the phthalates’ origin is discussed. Strong positive correlation between leaf damage and tetrapentacontane content in epicuticular waxes could presumably be the result of infection-induced metabolism reprogramming in epidermal cells of infected leaves.

Seasonal foliar uptake of atmospheric polycyclic aromatic hydrocarbons by some local plants in a tropical metropolis in India

This study explored the interspecies and seasonal variation of polycyclic aromatic hydrocarbons (PAHs) in the extracted lipids of the leaves of seven local plants in an urban environment of Kolkata (22°33′N and 88°20′E), India. Based on the degree of toxicity and carcinogenicity (expressed in terms of their Benzo(a)pyrene equivalent (BaPeq) concentrations) the overall foliar-PAH accumulation during the study period (September 2018‒;August 2019) in the various plants showed the following order: Nerium oleander (80.96 ± 30.08 ng.gdw−1) > Mangifera indica (74.15 ± 20.34 ng.gdw−1) > Lantana aculeata (60.13 ± 21.71 ng.gdw−1) > Thevetia peruviana (40.97 ± 12.45 ng.gdw−1) > Ixora coccinea (38.11 ± 9.5 ng.gdw−1) > Murraya paniculata (37.1 ± 7.35 ng.gdw−1) > Polyalthia longifolia (25.72 ± 5.71 ng.gdw−1). The PAHs like phenanthrene, anthracene, fluoranthene, pyrene, benzo(a)anthracene, chrysene, benzo (b+k)fluoranthene, benzo(a)pyrene, benzo [ghi]perylene and indeno [1,2,3-cd]pyrene were predominant during the study period over the PAHs like naphthalene, acynaphthylene, acenaphthene, fluorine and dibenz [a,h]anthracene in the extracted lipids. The temperature-dependent partitioning of the PAHs onto leaf-surface and photo-degradation could have affected the availability of the PAHs. The foliar PAH accumulation varied seasonally as winter (December–February) > postmonsoon (September–November) > premonsoon (March–May) > monsoon (June–August). The leaf epicuticular wax determined the PAH uptake and storage, which in turn was affected by the temperature and solar radiation. In consistence with the idea of “nature-based solutions” for deteriorated air quality remediation in an urban environment, this study could be a promising initiative to build up cost-effective biological filters to combat the airborne pollutants and improve urban air quality.