Adaxial Leaf Surface Research Articles

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

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. 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. 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.

Ergot Alkaloids and their Hallucinogenic Potential in Morning Glories.

Naturally occurring and semisynthetic ergot alkaloids play a role in health care or as recreational drugs in Western and indigenous Mexican societies. Evidence is summarized that ergot alkaloids present in Central American Convolvulaceae like Turbina corymbosa, Ipomoea violacea, and Ipomoea asarifolia are colonized by different species of a newly described clavicipitaceous fungal genus named Periglandula. The fungi are associated with peltate glandular trichomes on the adaxial leaf surface of its host plants. The Periglandula fungi are not yet culturable in vitro but were demonstrated to have the capacity to synthesize ergot alkaloids. The alkaloids do not remain in the fungal mycelium but are translocated via the glandular trichomes into their plant host. Both fungi and host benefit from a symbiotic lifestyle. In evolutionary terms the alkaloid biosynthetic gene cluster in the Periglandula/Ipomoea symbiosis is likely to have a conserved (basic) structure while biosynthetic ergot gene clusters within the genera Claviceps and Epichloe were under ecological selection for alkaloid diversification.

Quantitative trait loci mapping for stomatal traits in interspecific hybrids of Eucalyptus

Eucalyptus is an important industrial species with tolerance to drought and salt stress. Genetic improvement activities including quantitative trait loci (QTL) mapping for pulping and adventitious rooting traits are in progress, but no information is available on the genomic regions on adaptive traits such as stomatal characteristics. In this study, an interspecific cross between Eucalyptus tereticornis and E. grandis was generated for the development of genetic map and QTL identification for stomatal traits. Simple sequence repeats (SSRs), inter-simple sequence repeats (ISSRs) and sequence related amplified polymorphism (SRAP)markers were used for genotyping the F1 individuals. Parent-specific geneticmaps (female, 1023.56 cM;male, 1049.64cM) and consensus map (1049.4 cM) were developed. QTL analysis was carried out to identify the chromosomal regions affecting stomatal density, area and pore length in adaxial and abaxial leaf surface. Seven QTLs were identified with phenotypic variation of 11.36 to 27.30% for stomatal density, area and pore length. Correlation of stomatal traits when combined with growth and wood properties would have greater implications for generation of stress tolerant eucalypt hybrids with higher productivity and adaptability.

A robust vegetation index for remotely assessing chlorophyll content of dorsiventral leaves across several species in different seasons

BackgroundLeaf chlorophyll content (LCC) provides valuable information about plant physiology. Most of the published chlorophyll vegetation indices at the leaf level have been based on the spectral characteristics of the adaxial leaf surface, thus, they are not appropriate for estimating LCC when both the adaxial and abaxial leaf surfaces influence the spectral reflectance. We attempted to address this challenge by measuring the spectral reflectance of the adaxial and abaxial leaf surfaces of several plant species at different growth stages using a portable field spectroradiometer. The relationships between more than 30 published reflectance indices with LCC were analyzed to determine which index estimated LCC most effectively. Additionally, since the relationships determined on one set of samples might have poor predictive performances when applied to other samples, a robust wavelength region is required to render the spectral index generally applicable, regardless of the leaf surface or plant species.ResultsThe Modified Datt (MDATT) index, which is the ratio of reflectance difference defined as (Rλ3 − Rλ1)/(Rλ3 − Rλ2), exhibited the strongest correlation (R2 = 0.856, RMSE = 6.872 μg/cm2), with LCC of all the indices tested when all the leaf samples from the adaxial and abaxial surfaces were combined. The optimal wavelength regions, which were derived from the contour maps of R2 between the MDATT index and LCC for the datasets of one side or both leaf surfaces of each plant species and their intersection, indicated that the red-edge to near-infrared wavelength (723–885 nm) was optimal for λ1, while the red-edge region (697–771 nm) was optimal for λ2 and λ3. In these optimal wavelength regions, when the MDATT index was used to estimate LCC, an R2 higher than 0.8 could be obtained. The correlation of the MDATT index with LCC was the same when the positions of λ2 and λ3 were exchanged in the index.ConclusionsMDATT is proposed as an optimal index for the remote estimation of vegetation chlorophyll content across several plant species in different growth stages when reflectance from both leaf surfaces is considered. The red-edge to near-infrared wavelength (723–885 nm) for λ1, as well as the red-edge region (697–771 nm) for λ2 or λ3, are considered to be the most robust for constructing the MDATT index for estimating LCC, regardless of the leaf surface or plant species.

First report of downy mildew caused by Peronospora chlorae on lisianthus in Turkey

Lisianthus (Eustoma grandiflorum), also known as Texas bluebell, belongs to the family Gentianaceae. Lisianthus is a cut flower crop and is grown as an annual in İzmir, Turkey where greenhouse production exceeded 4 million plants produced from an area of 5.6 hectares in 2016 (Tüik, 1). In June 2017, plants showing severe downy mildew symptoms were observed in greenhouses in Menderes province. Under wet conditions, infected leaves turned yellow or pale green, with a greyish to brownish fungal-like downy growth developing on both the abaxial and adaxial leaf surface (Fig. 1). Leaf defoliation occurred at high disease severity and the remaining leaves withered. Infected leaves were collected for microscopic examination and morphological identification. A layer of sporangiophores was observed on symptomatic leaves, characteristic of a downy mildew. Sporangiophores were hyaline with long straight trunks and ended with two slightly curved branchlets. The sporangiophores were 200-480 × 4-11 μm. Sporangia were ovoid and hyaline, and measured 14-20 × 14-18 μm (Fig. 2). The pathogen was identified as Peronospora chlorae based on morphological characteristics (Hall, 2). DNA analysis was performed to confirm the identity of the pathogen. The internal transcribed spacer (ITS) region of rDNA was amplified and sequenced with primers ITS1 and ITS4 (White et al., 3) and the sequence was submitted to GenBank (Accession No. MG711454). A BLASTn analysis showed 100% identity to P. chlorae (KT271839), confirming the identity of the pathogen. For pathogenicity testing, infected leaves were collected and sporangia were washed from the diseased leaves with sterile water. Pathogenicity tests were performed by spraying lisianthus seedlings with the conidial suspension. Plants were then covered with plastic bags and incubated at 22-24°C with 90% relative humidity. Seven days post inoculation, sporangiophores were observed on infected lisianthus plants while no symptoms were observed on control plants. Peronospora chlorae has been previously reported from Denmark, France, Hungary, Italy, The Netherlands, Norway, Poland, Portugal, Spain, Switzerland, Ukraine, United Kingdom, the former Yugoslavia, Canada, Mexico, and China (Yang et al., 4). To our knowledge, this is the first report of P. chlorae causing downy mildew on lisianthus in Turkey.

Morphological diversity of β-diketone wax tubules on Eucalyptus gunnii leaves and real time observation of self-healing of defects in the wax layer

As part of the plant cuticle, epicuticular waxes build the boundary layer of a plant to its environment, fulfilling many vital functions. Epicuticular waxes are small crystalline structures which originate by self-assembly. The morphology of β-diketone tubules on Eucalyptus gunnii Hook.f. leaves was studied by field emission scanning electron microscopy (FE-SEM) and regeneration of removed waxes was investigated in real time by atomic force microscopy (AFM) on leaf surfaces. Smooth tubules as well as helically wound ribbons and transitional forms of tubules were found on adaxial leaf surfaces. Leaves of different developmental stages revealed no differences in their wax morphologies, but in the amount of wax allocation. After removal of the waxes regeneration was observed on leaves of all investigated ages. The regeneration of wax crystals started directly after wax removal and tubule growth could be observed in real time.

Correlation studies for shoot fly [Atherigona soccata (Rondani)] resistance traits in F3 generation of Sorghum [Sorghum bicolor (L.) Moench

Field screening of 120 F3 families of sorghum lines against shoot fly resistance was carried out at Millet Breeding Station, Tamil Nadu Agricultural University during Summer 2018. Leaf trichome density on adaxial and abaxial leaf surfaces showed significant negative correlation with oviposition preference of shoot fly on 14 and 21 days after emergence and dead heart incidence on 21 and 28 DAE. Leaf glossiness and seedling vigour rating scale showed high significant positive correlation with shoot fly oviposition and dead hearts. Genotypic correlation confirmed that the number of trichomes on both surfaces of lamina, leaf glossiness and seedling vigour contributed resistance to shoot fly. Thus these characters can be used as selection criteria for breeding shoot fly resistance genotypes.

First Report of Leaf Rust on Southern Highbush Blueberry caused by Thekopsora minima in California

Leaf rust symptoms have been intermittently observed on southern highbush blueberry (Vaccinium corymbosum L. × V. darrowii Camp) in California. Rust symptoms were first seen in 2010 near Carpinteria, CA (M. Kong, personal communication) and then in July 2016 on leaves of three blueberry cultivars Emerald, Jewel, and Snow Chaser in a field trial in Watsonville. In early 2017, leaf rust was observed again in Watsonville on the same cultivars and on various 3-year-old plants. Symptoms were found primarily on older leaves. Purplish-brown necrotic spots were present on the adaxial leaf surface, while the abaxial leaf side exhibited orange to yellow colored uredinia. Upon closer inspection using a light microscope, the uredinia were clustered on the leaf surface, ovoid in shape, and approximately 100 to 400 μm in diameter. Certain rust species possess ostiolar cells projections near the ostiole of the uredinium, which aid in taxonomic identification; however, ostiolar cells were not observed. Each uredinium contained numerous ellipsoid urediniospores with spines that emanated from the spore walls. When measured, urediniospores were 17.5 to 30 × 17.5 to 20 μm (average 24 × 19 μm, n = 25). Leaf samples with rust signs and symptoms were taken and stored at 4°C for further taxonomic examination. Potential alternate hosts (i.e., Tsuga spp.) for blueberry leaf rust were not present. After morphological evaluation, the rust pathogen was identified as Thekopsora minima P. Syd. & Syd. and two specimens from different plants were sent to the U.S. National Fungus Collection (BPI 910346 and BPI 910349) (Sato et al. 1993; Schilder and Miles 2011). DNA was extracted from six samples and two loci amplified from each sample. A 1,410-bp fragment spanning 5.8S-ITS2-28S rDNA was amplified with Rust2inv and LR6 primers (fragment 1) and a 1,697-bp fragment spanning the 18S rDNA was amplified with Rust18S-R and NS1 primers (fragment 2) (Aime 2006). Fragment 1 shared 100% identity (1,007 of 1,007 bp) with a T. minima isolate (BRIP57654) that infected V. corymbosum from Australia; fragment 2 shared >99% identity (1,207 of 1,210 bp) with the same isolate (accession nos. KC763340 and KT199391, respectively). Sequences for fragment 1 and fragment 2 from isolate (001) were deposited in GenBank (KY991374 and KY991375, respectively). Although another rust, Naohidemyces vaccinii, has been reported on V. membranaceum Douglas ex Torr. in CA, recent reports of T. minima in Australia, China, Mexico, South Africa, and in several states in the U.S. (OR, MI, DE, NY) suggest that T. minima is the most commonly encountered pathogen causing leaf rust on northern and southern highbush blueberries (Schilder and Miles 2011; Wiseman et al. 2016). To our knowledge, this is the first report of T. minima on any plant species within CA. In 2017, another rust species was found in Rubus spp. that was unobserved in CA previously, which could be related to significant winter precipitation (Shands et al. 2018). Since the alternate host Tsuga spp. is outside the central coast region of CA, further research is necessary to understand the epidemiology of T. minima in CA.

Behavioral thermoregulation in a small herbivore avoids direct UVB damage

Direct damage of increased solar ultraviolet-B (UVB) on organism fitness has attracted attention due to stratospheric ozone depletion. Although most ectotherms are not capable of detecting and avoiding solar UVB, they may avoid direct exposure to solar UVB via thermoregulation behavior. However, it is still not clear whether organisms are harmed by ambient UVB radiation before escaping to shaded microhabitats. In this study we used the English grain aphid, Sitobion avenae (Hemiptera: Aphididae), to test whether sunlight-avoidance behavior was caused by heat stress rather than UVB, and whether behavioral thermoregulation in shaded microhabitats contributes to avoidance or reduction of direct UVB damage. Our results showed that S. avenae tended to inhabit exposed adaxial leaf surfaces in mid-May in Mongolia, but inhabited shaded leaf surfaces in mid-June, thereby avoiding strong sunlight. Heat exposure rather than solar UVB was the primary reason for such avoidance behavior. The average and extreme temperatures of shaded leaf surfaces were several degrees lower than sunlight-exposed surfaces at midday, suggesting that movement to shaded leaf surfaces represents a form of behavioral thermoregulation. Such responses occurred before UVB radiation reached harmful levels, and contributed to avoiding direct UVB damage. As future climate warming is expected to lead to harmful UVB radiation as well as increasing temperatures, this may represent a case where responses to one stressor inadvertently protect against the harmful effects of a different stressor.

Secondary ion mass spectrometry imaging and multivariate data analysis reveal co-aggregation patterns of Populus trichocarpa leaf surface compounds on a micrometer scale.

Spatially resolved analysis of a multitude of compound classes has become feasible with the rapid advancement in mass spectrometry imaging strategies. In this study, we present a protocol that combines high lateral resolution time-of-flight secondary ion mass spectrometry (TOF-SIMS) imaging with a multivariate data analysis (MVA) approach to probe the complex leaf surface chemistry of Populus trichocarpa. Here, epicuticular waxes (EWs) found on the adaxial leaf surface of P. trichocarpa were blotted on silicon wafers and imaged using TOF-SIMS at 10μm and 1μm lateral resolution. Intense M+● and M-● molecular ions were clearly visible, which made it possible to resolve the individual compound classes present in EWs. Series of long-chain aliphatic saturated alcohols (C21 -C30 ), hydrocarbons (C25 -C33 ) and wax esters (WEs; C44 -C48 ) were clearly observed. These data correlated with the 7 Li-chelation matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) analysis, which yielded mostly molecular adduct ions of the analyzed compounds. Subsequently, MVA was used to interrogate the TOF-SIMS dataset for identifying hidden patterns on the leaf's surface based on its chemical profile. After the application of principal component analysis (PCA), a small number of principal components (PCs) were found to be sufficient to explain maximum variance in the data. To further confirm the contributions from pure components, a five-factor multivariate curve resolution (MCR) model was applied. Two distinct patterns of small islets, here termed 'crystals', were apparent from the resulting score plots. Based on PCA and MCR results, the crystals were found to be formed by C23 or C29 alcohols. Other less obvious patterns observed in the PCs revealed that the adaxial leaf surface is coated with a relatively homogenous layer of alcohols, hydrocarbons and WEs. The ultra-high-resolution TOF-SIMS imaging combined with the MVA approach helped to highlight the diverse patterns underlying the leaf's surface. Currently, the methods available to analyze the surface chemistry of waxes in conjunction with the spatial information related to the distribution of compounds are limited. This study uses tools that may provide important biological insights into the composition of the wax layer, how this layer is repaired after mechanical damage or insect feeding, and which transport mechanisms are involved in deploying wax constituents to specific regions on the leaf surface.

Four distinct leaf types in the Brazilian Cerrado, based on bundle sheath extension morphology

Plant species have been classified as being either heterobaric or homobaric based on the presence or absence (respectively) of bundle sheath extensions (BSE) in leaf veins. These leaf types differ in their physiological performance, and their occurrences tend to be associated with environment. This study investigated the presence/absence of BSE and their structural peculiarities in 49 woody species (28 angiosperm families) in the Brazilian Cerrado using anatomical methods. We measured the gas exchange indices and stomatal density. In addition to typical homobaric (61.2%) and heterobaric (22.4%) species, we also found species with intermediate BSE features. These we call “larger heterobaric” (12.2%) and “semi-heterobaric” (4.1%) species. In the former, BSE occurs around only the secondary veins, whereas in the latter the BSE projects only towards the adaxial leaf surface. The net CO2 assimilation rates, the stomatal conductance, the transpiration rates, and the carboxylation efficiencies were statistically higher in heterobaric than in homobaric species. In the larger heterobaric species, the photosynthetic indices were similar to those in the heterobaric species. Meanwhile, semi-heterobaric species showed photosynthetic indices similar to the homobaric species. We demonstrated that structural variation in the BSE is linked to physiological leaf performance, suggesting some correlation between leaf morphology and plant adaptations.

Populus luzae (Salicaceae), a new species of white poplar endemic to the western Transmexican Volcanic Belt, in Zapopan, Jalisco, Mexico

Populus luzae, a new species of white poplar from the western Transmexican Volcanic Belt, Zapopan, Jalisco, Mexico, is described and illustrated. Populus luzae belongs to section Populus and is morphologically close to P. guzmanantlensis, but it differs from the latter in having smaller size and soboliferous habit, narrower twigs and petioles, ovate to ovate-deltoid and chartaceous leaf blades, adaxial leaf surface with less depressed veins, abaxial surface puberulent, thrice smaller ovate male bracteoles with entire margin, twice longer female bracteoles sparsely denticulate but none lobed, smaller number of pistillate flowers, capsules pubescent, twice longer mature male inflorescence, and a lax and longer infrutescence.

First Report of Leaf Rust on California Blackberry (Rubus ursinus) Caused by Kuehneola uredinis in California

In 2017, several wild California blackberry plants (Rubus ursinus Cham. & Schldl.) were observed with symptoms of leaf rust and severe defoliation within Monterey County, CA (GPS coordinates N 36°35′33.025″ W 121°49′58.67″). Representative samples (n = 5) were collected and stored at 4°C. Symptoms appeared primarily on older leaf surfaces and leaf edges. The adaxial leaf surface had circular to angular spots surrounded by brown necrotic tissue, and the abaxial surface had bright yellow-orange rust pustules (uredinia). Uredinia were erumpent and were 100 to 400 µm in diameter. Urediniospores were broadly obovoid, pale yellow-orange in color, and measured 28 to 40 × 24 to 32 µm (average 33 × 27 µm, n = 25) with echinulate spore walls 1.0 to 1.5 µm thick. Based on morphology and host information, the pathogen was identified as Kuehneola uredinis (Link) Arth., and a sample was deposited in the U.S. National Fungus Collection (BPI 910348) (Arthur 1906). To confirm this identification, DNA was extracted from urediniospores of one representative sample, and two separate PCR reactions were performed. A 1,755-bp fragment spanning 5.8S-ITS2-28S gene region of rDNA was amplified with Rust2inv and LR6 primers (fragment 1), and a 2,684-bp fragment spanning the 18S gene region of rDNA was amplified with Rust18S-R and NS1 primers (fragment 2) (Aime 2006). PCR products were sequenced with primers LR3 and LR0R (28S gene region) and NS5, NS6, and NS4 (18S gene region), described in Aime (2006). Fragment 1 shared 99% identity with a K. uredinis isolate (HMUT100497) from China (GenBank accession KU059177). Fragment 2 shared 98% identity with a Phragmidium sp. isolate (MB) from the United States (GenBank accession EF014363). The sequence match to the Phragmidium sp. isolate (MB) was likely owing to the absence of the 18S sequence of K. uredinis in the GenBank database. Sequences were deposited for fragment 1 and fragment 2 (GenBank accessions MF158087 and MF158088, respectively). To confirm the Rubus spp., genomic DNA was extracted from leaf tissue, and PCR was performed using ITS1 and ITS4 primers found in White et al. (1990). The product was sequenced with the amplification primers and shared 100% identity with R. ursinus internal transcribed spacer 1 and 2 (GenBank accession AF055794). R. ursinus is known as a parent of the loganberry (Rubus × loganobaccus L.H. Bailey), which is commercially grown and cultivated. K. uredinis has been reported on R. ursinus in Australia, New Zealand, and South Africa, and within the United States in Washington (Shaw 1973). K. uredinis has been reported in California on Santa Catalina Island on R. vitifolius Cham & Schldl., which is often a synonym of R. ursinus, but throughout the literature these are often described as distinct species (Millspaugh and Nuttall 1923). To our knowledge K. uredinis has never been reported in mainland California on R. ursinus or R. vitifolius. This is of particular concern given that (i) urediniospores disperse long distances by wind and (ii) several Rubus spp. (e.g., blackberry, loganberry, and raspberry) are susceptible in California and are economically important crops within 20 km of this reported observation.

Wheat flag leaf epicuticular wax morphology and composition in response to moderate drought stress are revealed by SEM, FTIR-ATR and synchrotron X-ray spectroscopy.

Wheat (Triticum aestivum L.) is the largest cereal crop grown in Western Canada where drought during late vegetative and seed filling stages affects plant development and yield. To identify new physiochemical markers associated with drought tolerance, epidermal characteristics of the flag leaf of two wheat cultivars with contrasting drought tolerance were investigated. The drought resistant 'Stettler' had a lower drought susceptibility index, greater harvest index and water-use efficiency than the susceptible 'Superb'. Furthermore, flag leaf width, relative water content and leaf roll were significantly greater in Stettler than in Superb at moderate drought stress (MdS). Visible differences in epicuticular wax density on the adaxial flag leaf surfaces and larger bulliform cells were identified in Stettler as opposed to Superb. Mid-infrared attenuated total internal reflectance spectra revealed that Stettler flag leaves had increased asymmetric and symmetric CH2 but reduced carbonyl esters on its adaxial leaf surface compared to Superb under MdS. X-ray fluorescence spectra revealed a significant increase in total flag leaf Zn concentrations in Stettler in response to MdS. Such information on the microstructural and chemical features of flag leaf may have potential as markers for drought tolerance and thereby accelerate the selection and release of more drought-resistant cultivars.

First Report of Powdery Mildew Caused by Blumeria graminis on Avena sativa in China

Oat (Avena sativa) is extensively planted as a fodder crop and most of the production is used for livestock feed in China (Yang et al. 2010). In March 2017, powdery mildew was observed on A. sativa in the Forage Germplasm Nursery (30.47785° N, 103.75878° E) in Xinjin county, Sichuan Province, China. Approximately 40% of plants (about 0.2 ha in total) were affected. The symptoms initially appeared as irregular white mycelial colonies on the adaxial leaf surface. Subsequently, the colonies increased in numbers and size, later covered a large area of leaf and stem. In advance stage of infection, white patches turned into sunken reddish-brown lesions on leaf surface and eventually caused leaf death. The hyphae were flexuous, septate, branched, and 2.6 to 7.6 μm (n = 20) wide. The well developed appressoria on the hyphae were observed with diameter between 3.2 and 6.3 μm (n = 10). Conidiophores were unbranched and cylindrical with swollen bases, measuring 6.3 to 13.2 × 23.4 to 67.5 μm (n = 20), and borne verti...

Herbivory by leaf-cutter ants changes the glandular trichomes density and the volatile components in an aromatic plant model.

Herbivory can induce several structural and functional alterations in the plant secretory system. Glandular trichomes are the main sites of production of volatile organic compounds (VOCs) with several chemical properties in Lamiaceae species. Ocimum species usually have three morphotypes of glandular trichomes (morphotype I is peltate and has a wide four-celled head; morphotype II is capitate and has a unicellular head; and morphotype III is capitate with a bicellular head) which produce a great amount of terpenes, although other chemical categories of substances are also produced. Despite the abundance of trichomes producing important anti-herbivory components in their leaves, the association between Ocimum species and leaf-cutter ants has been commonly registered in Brazil. We investigated the effect of leaf-cutter ant attack on the density of the glandular trichomes and on the chemistry of the VOCs released from leaves of O. gratissimum. Plants were subjected to Acromyrmex rugosus attack until 90 % of leaves were removed. After 40 days from the leaf-cutter attack, both treatments were sampled. The glandular trichome density was analysed by scanning electron microscopy. The VOCs were extracted utilizing headspace solid-phase microextraction (HS-SPME) technique and analysed by gas chromatography. Generally, the density of glandular trichomes increased in the adaxial leaf surface of the attacked plants. However, we bring novelties on this topic since we analysed the density of each morphotype separately. The morphotype I decreased in the abaxial leaf surface, and increased in the adaxial leaf surface; the morphotype II increased in both leaf surfaces; and the morphotype III decreased in the abaxial leaf surface and remained constant in the adaxial leaf surface of attacked plants. In leaves of attacked plants, the (Z)-β-ocimene increased by 50 %, the α-selinene by 13 % and the germacrene D by 126 %, whereas the eugenol decreased by 70 %. Our data point to a differential response of each glandular morphotype in O. gratissimum and are consistent with the idea of a compartmentalization of functions among the different glandular morphotypes in the plant defence against environmental factors.

Characterization of trichome morphology and aphid resistance in cultivated and wild species of potato

Trichomes are specialized epidermal structures that protect plants from abiotic and biotic stresses. Cultivated potato (Solanum tuberosum) is known to have both glandular and non-glandular trichomes. However, the criteria for trichome type classification have not been studied in detail. In addition, there is a poor understanding of the types of trichomes that exist in wild potato species. Here, the morphology and density of trichomes were compared between a representative cultivated potato variety and 17 wild potato species using Cryo Scanning Electron Microscopy (CryoSEM). Based on trichome morphology, the cultivated variety and each of the wild species were seen to have two glandular and two non-glandular trichome types. We classified the eighteen potato species into four groups using trichome type and density criteria. Groups I and II represented species with a higher density of glandular or non-glandular trichomes, respectively, on both abaxial and adaxial leaf surfaces. Group III represented species with a higher density of non-glandular trichomes on abaxial leaf surfaces alone. Group IV represented species with an overall lower trichome density on both abaxial and adaxial leaf surfaces, but which was formed of both glandular and non-glandular types. Honey dew spots were quantified following infestation with the aphid Macrosiphum euphorbiae to test whether trichome composition is associated with resistance to aphid feeding. Fewer honey dew spots were observed in the Group I representative species S. berthaultii and S. hougasii compared to that in species from other groups. Furthermore, correlation coefficient analysis showed that honey dew spot number was negatively associated with glandular trichome density. These results imply that glandular trichomes play an important role in aphid resistance and thus can be used for developing insect-resistant potato.

Integrated Physiological, Biochemical, Anatomical and Molecular Studies Reveals Salt Stress Responsive Mechanism Associated with Popular Rice Land-Races in Eastern Part of India

The present study aims towards examining physiological, biochemical, anatomical and molecular traits in the high-yielding rice landraces of the eastern part of India at germination and seedling stage for low-to-moderate salinity stress tolerance. The germination percentages of 12 high-yielding varieties were analyzed under seven different concentrations of salt (0, 50, 100, 150, 200, 250 and 300 mM). Although, Lalat performed very well with 63.66 % germination rate at 300 mM salt stress conditions, higher levels of salinity exhibited detrimental effects on other varieties. Hence, the salt concentrations 150 mM and 250 mM were optimally selected to screen the varieties for physiological and biochemical traits. The high-yielding varieties Lalat, Vamsi and Pratiksha exhibited lowest and similar trend of reduction over control (ROC) with relative water content (RWC) for 250 mM salt concentrations. The level of proline, increased with increasing concentrations of NaCl among most of the varieties and significantly high content was found in Vamsi. The chlorophyll content was high in Lalat as well as Pratiksha and reduction over control was highest in Vamsi under 150 mM salt concentrations. Interestingly, Lalat emerged as the most salt-tolerant landrace for physiological and biochemical traits. It was compared with salt-sensitive MTU7029 for anatomical changes on adaxial surface of the leaf blade and noticed out to be with less widened and few number of stomatal pores in response to salt stress. Further, expression analysis of salt-specific genes OsHKT1;5 and OsNHX1 resulted in identification of novel salt-stress responsive alleles/motifs like W-boxes, Box-W1, E2Fb and MBS in Lalat (salt-tolerant). Thus, the study disclosed the anatomical changes in adaxial surface of leaf and association of potential cis-acting regulatory elements (CARE) in regulation of salt-stress responsiveness in these two-contrasting rice landraces in the eastern part of India. Further, the study laid a foundation to explore transcriptional gene regulation to open-up the pathway towards crop improvement for salt-stress tolerance.

Electron microscopic observations of sooty moulds on crape myrtle leaves

SummarySooty moulds on crape myrtle leaves were investigated using light and electron microscopy. The adaxial leaf surface was distinctly covered with soot‐like masses of dark brown hyphae and conidia. The main characteristics of the sooty moulds included stauroconidia, conidial clusters, hyphal degeneration and extracellular melanin depositions. Some conidia were round, measured ~10 μm in diameter, and mostly one‐septate; others were branched and multiseptate (stauroconidia). Based on their morphology, the sooty moulds were determined to consist of several component fungal species belonging to genera such as Antennaria, Metacapnodium and Tripospermum. Enclosed in electron‐dense melanin layers, hyphae and conidial clusters had concentric bodies exhibiting electron‐transparent cores and electron‐dense shells with fibrillar sheaths. Concentric bodies are hypothesized to function as multilayer lipid‐encapsulated nanobubbles or eukaryotic gas vesicles for cytoplasmic volume control. Intrahyphal hyphae possessed electron‐dense cytoplasm and lipid globules. These results suggest that sooty moulds are equipped with melanized cell walls, multicelled resting structures, hyphal regeneration, intrahyphal growth and gas vesicles to adapt to their xeric phylloplane environment. Condensed and elongated starch granules in the chloroplasts of mesophyll tissues may indicate the acclimation of the sooty leaf regions to light reduction and temperature increase.

Peltaspermalean seed ferns with preserved cuticle from the Upper Triassic Karamay Formation in the Junggar Basin, northwestern China

Foliage of a new peltaspermalean seed fern is described on the basis of a large collection of well-preserved plant adpressions with cuticle from the Upper Triassic Karamay Formation in Xinjiang Province, NW China. Pinnae are lanceolate with undulate-dentate margins and with fascicular lateral veins in lobes. Tertiary veins are simple as are interfascicular veins that occur between fascicular lateral veins. Cuticles are thick, amphistomatic, with abaxial and adaxial cuticles being similar to each other and having clear costal and intercostal areas. Stomata are sunken and randomly distributed on both the abaxial and the adaxial cuticle. The stomatal complex is monocyclic and comprises 4–7 subsidiary cells. Papillae are present on ordinary cells and on subsidiary cells surround the stomatal aperture. The adaxial leaf surface has a stomatal index of 3.27 and an average stomatal density of 15permm2, whereas the abaxial surface has a stomatal index of 5.25 and an average stomatal density of 30permm2. This is the first report of the cuticular structure of Scytophyllum from the Junggar Basin, which now enables detailed comparison with other species of the genus from Eurasia. Analysis of the sedimentary succession containing Scytophyllum suggests a humid or seasonally dry environment, but the thick cuticles with sunken stomata and abundant papillae indicate that the plant was adapted to living in water-stressed conditions.