Foliar Trichomes Research Articles

Infraspecific variations in essential oil and glandular trichomes in Nepeta heliotropifolia

Yarmoohammadi M, Talebi SM, Nohooji MG. 2017. Infraspecific variations in essential oil and glandular trichomes in Nepeta heliotropifolia. Biodiversitas 18: 964-970. Nepeta heliotropifolia Lam. (Labiatae) is one of the perennial medicinal and aromatic plants, naturally grows in different regions of Iran. The essential oil composition of aerial parts and also the micromorphology and distribution of foliar trichomes of N. heliotropifolia from two different regions of Iran were studied. The extracted essential oils were significantly composed of caryophyllene oxide and phytol, which were quantified by GC and identified based on their GC/MS spectra. The essential oil compositions differed greatly with habitat as well as former investigations. Phytol was quantified between 0.75-10. 29% of the total essential oil, but caryophyllene oxide was quantified between 3.90-12.17% of the total essential oil. Trichomes investigations showed that leaves bear an indumentum of glandular and non-glandular hairs. Two main kinds of glandular trichomes were observed; peltate and capitate. The numbers of capitate and peltate trichomes varied between populations. Such great differences in the essential oil composition may be attributed to chemotype creation and also an adaptation of these populations to particular habitats.

Oviposition, larval survival and leaf damage by the willow leaf blotch miner, Micrurapteryx salicifoliella, in relation to leaf trichomes across 10 Salix species

1. Foliar trichomes clearly reduce chewing damage and efficiency of movement by some insect herbivores, but the effect of trichomes on insect oviposition is less well characterised. Trichomes are likely to have particularly strong, negative effects on species that require secure attachment of the egg to the leaf epidermis for successful transition to the feeding stage – a group that includes many leaf mining insects.2. One such species, Micrurapteryx salicifoliella, must initially enter leaf cells directly from an egg adhered to the cuticle, but later instars can move between leaves and initiate new mines from the leaf exterior.3. Natural patterns of occurrence by M. salicifoliella were quantified on 10 sympatric Salix species varying in trichome expression to test whether trichomes were associated with reduced oviposition, larval survival and leaf damage.4. Mean egg density and leaf mining damage were negatively related to mean trichome density across Salix species. Survival of M. salicifoliella from egg to pupa was positively related to trichome density, suggesting that initiation of new mines by late‐instar larvae was not adversely affected by trichomes. There was no evidence that trichomes benefited leaf miner larvae indirectly by decreasing density‐dependent mortality; rather, the positive relationship between trichome density and larval survival may reflect less effective chemical defence by Salix species expressing high trichome density.5. The results suggest that foliar trichomes serve as an effective defence against M. salicifoliella by deterring oviposition, but do not reduce the survivorship of those individuals that successfully transition from egg to larva.

Epifluorescence and Stereomicroscopy of Trichomes Associated with Resistant and Susceptible Host Plant Genotypes of the Asian Citrus Psyllid (Hemiptera: Liviidae), Vector of Citrus Greening Disease Bacterium.

Background and Significance:Foliar trichomes (tiny hair-like structures) are part of the plant defense mechanisms that may confer resistance to some herbivore pests. Trifoliate orange, Poncirus trifoliata, is a genotype resistant to infestations by the Asian citrus psyllid, Diaphorina citri (Hemiptera: Liviidae), vector of the economically important citrus greening (huanglongbing) disease bacterium. We discovered that dense trichomes are associated with young leaves of trifoliate orange plants and hypothesized that these might be responsible for reduced infestation by this psyllid.Materials and Methods:Epifluorescence and stereomicroscopy were used to study the density and structure of trichomes associated with young flush leaves and stems of trifoliate orange and of five other plant genotypes that are highly susceptible to colonization by the psyllid: lemon, grapefruit, sweet orange, curry leaf, and orange jasmine.Results:Simple unicellular trichomes were observed at moderate-to-large densities on young leaves and stems of each genotype except lemon and sweet orange, which had considerably fewer trichomes. Trichomes were generally abundant on young leaves of curry leaf and orange jasmine, two genotypes that are often heavily colonized by the psyllid. Although we did not quantify oviposition rates on these genotypes, we observed that psyllid females deposited eggs on young leaves, buds, and stems regardless of the density of trichomes present, sometimes directly within or close to a dense bed of trichomes.Conclusions:While trichomes were moderately abundant on young leaves of trifoliate orange, our results strongly suggest that these trichomes may play little or no role in reduced colonization by the psyllid on this genotype.

Survey of Foliar Trichomes in Combretum Loelf. (Combretaceae) in Parts of West Africa

We studied the foliar trichome types, density and distribution among the genus Combretum Loelf. in parts of West Africa. Fresh and herbarium specimens were used. These specimens were fixed, peeled, trichome types identified and micro-photographed using a Leica WILD MPS 52 microscope camera on a Leitz Diaplan microscope. Generally, two major trichome groups were identified among these species studied. These include glandular trichomes: multicellular gland head with uniseriate stalk (MGU), cylindrical uniseriate clavate trichome (CUCT), unicellular gland with unisariate stalk (UGHU), cylindrical uniseriate trichome (CUT), paltate gland head (PGH) and combretaceous eglandular (non-glandular) conical trichome (long and short types). The eglandular trichome types were the most widely distributed trichome found in the species and could be used to distinguish the genus. They occurred in all the species studied except C. glutinosum and C. micranthum. Among the glandular trichomes, cylindrical uniseriate trichome was the most dominant occurring in 11 species namely; C. aculeatum, C. bracteatum, C. collinum subsp. binderianum, C. collinum subsp. hypopilinum, C. constrictum, C. capitatum, C. hispidum, C. nigricans, C. panuculatum, C. platypterum and C. zenkeri. This is followed by multicellular gland head with uniseriate stalk (MGU) trichome type which occurred in 9 species (C. bracteatum, C. collinum subsp. binderianum, C. collinum subsp. hypopilinum, C. constrictum, C. excelsum, C. hispidum, C. mooreanum, C. platypterum and C. racemosum). The trichome density varied from 1.25±0.44 trichomes per 100 cells to 600 trichomes per 100 cells. The distribution/occurrence, density and type of these trichomes formed dependable character for delimitating Combretum species. The findings of this study showed that trichomes provide good taxonomic characters useful for in differentiating the genus Combretum in West Africa.

Are the wing's cells alive? Study case in Vriesea trichomes

Abstract The presence of peltate foliar trichomes is one of the main anatomical characteristic of Bromeliaceae. These complex structures are adapted to compensate water and nutrient absorption in species that have reduced or substrate and light-reflection independent roots. They have enabled species' survival in diverse and extreme environments contributing to the wide distribution of this family. In the present work, we analyzed the peltate trichomes' characteristics in three taxa of Vriesea (Tillandsioideae): Vriesea platynema var. platynema, V. platynema var. variegata and V. tijucana. Leaves in different developmental stages were analyzed with histochemical tests and Transmission Electron Microscopy. Main results include the presence of cytoplasmic content in the wing peripheral cells, as well as in mature leaves. This is the first register of the presence of such feature in this family, which brings the possibility of discussing how water can be absorbed by these cells.

Effects of stress on foliar trichomes plasticity in Mentha piperita

Effects of stress on foliar trichomes plasticity in Mentha piperita

Erratum to: Distribution, morphological and histochemical characteristics of foliar trichomes of Plectranthus zuluensis (Lamiaceae)

There are problems in the delimitation/identification of Plectranthus species and this investigation aims to contribute toward solving such problems through structural and histochemical study of the trichomes. Considering the importance of P. zuluensis as restricted to semi-coastal forests of Natal that possess only two fertile stamens not four as the other species of this genus. The objective of this work was to study in detail the distribution, morphology and histochemistry of the foliar trichomes of this species using light and electron microscopy. Distribution and morphology of two types of non-glandular, capitate and peltate glandular trichomes are described on both leaf sides. This study provides a description of the different secretion modes of glandular trichomes. Results of histochemical tests showed a positive reaction to terpenoids, lipids, polysaccharides and phenolics in the glandular trichomes. We demonstrated that the presence, types and structure of glandular and non-glandular trichomes are important systematic criteria for the species delimitation in the genus.

The contribution of microorganisms and metazoans to mineral nutrition in bromeliads

One critical challenge for plants is to maintain an adequate nutrient supply under fluctuating environmental conditions. This is particularly true for epiphytic species that have limited or no access to the pedosphere and often live in harsh climates. Bromeliads have evolved key innovations such as epiphytism, water-absorbing leaf trichomes, tank habit and Crassulacean acid metabolism (CAM) photosynthesis that enable them to survive under various environmental conditions. Bromeliads encompass diverse ecological types that live on different substrates (they can be terrestrial, epilithic or epiphytic) and vary in their ability to retain water (they can be tank-forming or tankless) and photosynthetic pathway (i.e. C3 or CAM). In this review, we outline the nutritional modes and specializations that enable bromeliads to thrive in a wide range of nutrient-poor (mostly nitrogen-depleted) environments. Important Findings Bromeliads have evolved a great diversity of morphologies and functional adaptations leading to the existence of numerous nutritional modes. Focusing on species that have absorptive foliar trichomes, we review evidence that bromeliads have evolved multi-faceted nutritional strategies to respond to fluctuations in the supply of natural nitrogen (N). These plants have developed mutualistic associations with many different and functionally diverse terrestrial and aquatic microorganisms and metazoans that contribute substantially to their mineral nutrition and, thus, their fitness and survival. Bacterial and fungal microbiota-assisted N provisioning, protocarnivory, digestive mutualisms and myrmecotrophic pathways are the main strategies used by bromeliads to acquire nitrogen. The combination of different nutritional pathways in bromeliads represents an important adaptation enabling them to exploit nutrient-poor habitats. Nonetheless, as has been shown for several other vascular plants, multiple partners are involved in nutrient acquisition indicating that there have been convergent adaptations to nutrient scarcity. Finally, we point out some gaps in the current knowledge of bromeliad nutrition that offer fascinating research opportunities.

Geographic variation in the protective effects of ants and trichomes in a Neotropical ant–plant

Many ant–plants have pubescent leaves, but the extent to which leaf trichomes enhance the defensive capabilities of ant–plants is poorly known. Here, we examined the influence of foliar trichomes and ants on herbivory in the Neotropical ant–plant Tococa guianensis. We performed a feeding preference test and a field experiment in which we manipulated the presence of ants and trichomes in three distinct populations of T. guianensis; two associated with obligate mutualistic ants and one associated with opportunistic ants. We found that both mutualistic ants and leaf trichomes act as mechanisms of defense against herbivores in T. guianensis. However, the relative importance of each of these two mechanisms was context dependent. The magnitude of the effect of trichomes (as measured by the effect size) was relatively low and varied little among plant populations. The effect of ants on foliar herbivory was up to seven times stronger than the effect of the trichomes. Nevertheless, because the magnitude of ant effects was spatially variable—depending on whether mutualistic ants were present or not, and probably also on the local abundance of herbivores—the relative contribution of ants and trichomes for plant defense was also spatially variable. These findings indicate that mechanical defenses (leaf trichomes) alone cannot replace the biotic defenses of T. guianensis. However, trichomes can play a comparatively more important role in plant defense at times or places where mutualistic ants are not present.

Micromorphology, histochemistry and ultrastructure of the foliar trichomes of Withania somnifera (L.) Dunal (Solanaceae)

The leaves of Withania somnifera contained four morphologically distinct trichome types: glandular capitate, non-glandular dendritic (branched), non-glandular bicellular and non-glandular multicellular trichomes. Major phytochemical compounds present within glandular and non-glandular trichomes were alkaloids and phenolic compounds. The aim of this study was to characterize the micromorphology of the foliar trichomes of Withania somnifera as well as to elucidate the location and composition of the secretory products. Trichome density and length was also determined in three developmental stages of the leaves. Light microscopy and scanning electron microscopy showed the presence of four morphologically distinct trichome types: glandular capitate, non-glandular dendritic, non-glandular bicellular and non-glandular multicellular. The dendritic trichomes exhibited cuticular warts which are involved in the "Lotus-Effect". Glandular capitate and non-glandular dendritic trichomes were aggregated on the mid-vein of young and mature leaves, possibly to protect underlying vasculature. Histochemical staining also revealed the presence of two major classes of phytochemical compounds that are of medicinal importance, i.e. alkaloids and phenolic compounds. These compounds are used to treat a wide variety of ailments and also act as chemical deterrents in plants. The results of this study explain possible roles of four morphologically distinct trichome types based on their morphology, foliar distribution and content.

Foliar trichome-aided formaldehyde uptake in the epiphytic Tillandsia velutina and its response to formaldehyde pollution

Epiphytic Tillandsia (Bromeliaceae) species have been found to be efficient biomonitors of atmospheric heavy metals and persistent organic pollutants, but have not been used to monitor or remove the primary indoor atmospheric pollutant formaldehyde (FA). The absorptive capacity of Tillandsia trichomes is well-established, but potential secondary effects of foliar trichomes on gas exchange remain unclear. Our study investigated whether Tillandsia species can absorb FA efficiently and if the leaf trichomes function to improve FA uptake, using Tillandsia velutina. Plants with intact trichomes, decreased FA concentration by 48.42% in 12h from 1060μgm−3 to 546.67μgm−3, while FA concentration decreased only by 22.51% in the plants without trichomes. Moreover, the more trichomes removed from the leaves, the lower the capability of FA uptake per unit leaf area, which suggested that T. velutina was capable of absorbing a large amount of FA via the leaves and specialized trichomes facilitated the whole leaf tissue FA absorption. In addition, all plants exposed to FA were chloric, had a reduction in measured leaf chlorophyll, and an increment in permeability of plasma membranes. However, plants in which trichomes had been removed declined or increased more quickly than plants with intact trichomes, indicating Tillandsia leaf trichomes also give the leaves some protection against this toxin.

Transcriptome profiling reveals roles of meristem regulators and polarity genes during fruit trichome development in cucumber (Cucumis sativus L.).

Trichomes are epidermal hair-like structures that function in plant defence against biotic and abiotic stresses. Extensive studies have been performed on foliar trichomes development in Arabidopsis and tomato, but the molecular mechanism of fruit trichome formation remains elusive. Cucumber fruit is covered with trichomes (spines) that directly affect the appearance and quality of cucumber products. Here, we characterized the fruit spine development in wild-type (WT) cucumber and a spontaneous mutant, tiny branched hair (tbh). Our data showed that the cucumber trichome was multicellular and non-glandular, with malformed organelles and no endoreduplication. Fruit spine development was generally homogenous and marked by a rapid base expansion stage. Trichomes in the tbh mutant were tiny and branched, with increased density and aberrant cell shape. Transcriptome profiling indicated that meristem-related genes were highly enriched in the upregulated genes in the tbh versus the WT, as well as in WT spines after versus before base expansion, and that polarity regulators were greatly induced during spine base expansion. Quantitative reverse transcription PCR and in situ hybridization confirmed the differential expression of CUP-SHAPED COTYLEDON3 (CUC3) and SHOOT MERISTEMLESS (STM) during spine development. Therefore, cucumber trichomes are morphologically different from those of Arabidopsis and tomato, and their development may be regulated by a distinct pathway involving meristem genes and polarity regulators.

Elevated CO2 alters the feeding behaviour of the pea aphid by modifying the physical and chemical resistance of Medicago truncatula.

Elevated CO(2) compromises the resistance of leguminous plants against chewing insects, but little is known about whether elevated CO(2) modifies the resistance against phloem-sucking insects or whether it has contrasting effects on the resistance of legumes that differ in biological nitrogen fixation. We tested the hypothesis that the physical and chemical resistance against aphids would be increased in Jemalong (a wild type of Medicago truncatula) but would be decreased in dnf1 (a mutant without biological nitrogen fixation) by elevated CO(2). The non-glandular and glandular trichome density of Jemalong plants increased under elevated CO(2), resulting in prolonged aphid probing. In contrast, dnf1 plants tended to decrease foliar trichome density under elevated CO(2), resulting in less surface and epidermal resistance to aphids. Elevated CO(2) enhanced the ineffective salicylic acid-dependent defence pathway but decreased the effective jasmonic acid/ethylene-dependent defence pathway in aphid-infested Jemalong plants. Therefore, aphid probing time decreased and the duration of phloem sap ingestion increased on Jemalong under elevated CO(2), which, in turn, increased aphid growth rate. Overall, our results suggest that elevated CO(2) decreases the chemical resistance of wild-type M. truncatula against aphids, and that the host's biological nitrogen fixation ability is central to this effect.

Evolutionary changes in plant tolerance against herbivory through a resurrection experiment

Both theoretical and empirical works have highlighted the difference in the evolutionary implications of host resistance and tolerance against their enemies. However, it has been difficult to show evolutionary changes in host defences in natural populations; thus, evaluating theoretical predictions of simultaneous evolution of defences remains a challenge. We studied the evolutionary changes in traits related to resistance and tolerance against herbivory in a natural plant population using seeds from two collections made in a period of 20 years. In a common garden experiment, we compared defensive traits of ancestral (1987) and descendant (2007) subpopulations of the annual plant Datura stramonium that shows genetic variation for tolerance and to which the specialist herbivore Lema daturaphila is locally adapted. We also examined the effects of different plant genotypes on the herbivore for testing the plant genetic variation in resistance. Based on the response to the contemporary herbivore populations, results revealed a nonsignificant response in plant resistance traits (herbivore consumption, foliar trichomes and tropane alkaloids), but a significant one in tolerance. The survival of herbivores in laboratory experiments depended on the plant genotype, which suggests genetic variation in plant resistance. Although we cannot identify the selective agent for the change nor exclude genetic drift, the results are consistent with the expectation that when resistance fails to control herbivory, tolerance should play a more important role in the evolution of the interaction.

Two new species of Miconia (Melastomataceae: Miconieae) from the cloud forests of Panama

Two new species, Miconia galdamesiae and M. papillopetala are described from cloud forests of western Panama. Both species belong to a clade of Costa Rican and Panamanian taxa that typically have asymmetric leaf venation, flowers with calyces that are fused in bud but rupture into irregular lobes at anthesis, geniculate staminal filaments, five locular ovaries that are glandular-puberulent apically, exerted styles (herkogamous), and angulate seeds. The affinities of the new taxa are discussed and compared with presumed closest relatives and a comparative table is provided. Photographs of live plants and Scanning Electron Micrographs of foliar trichomes, flower buds, and whole flowers at anthesis are included for the new taxa as well as for Miconia brenesii and M. friedmaniorum, two closely related species that have been confused with the new taxa described here.

Foliar trichomes of <i>Croton</i> L. (Euphorbiaceae: Crotonoideae) from China and its taxonomic implications

Foliar trichomes of 21 species of the genus Croton L. from China have been examined using stereomicroscopy and scanning electron microscopy. Five trichome types characterized by their morphology are identified, viz., stellate, lepidote, simple, dendritic and appressed-rosulate. Only stellate trichome is observed in most species, with only six species that are found to maintain two or three trichome types. Trichome types and density are useful for species identification and sectional classification for Chinese species. Based on the trichome types and other morphological characters, 21 Chinese species are proposed to be placed in five sections. Croton crassifolius belongs to sect. Andrichnia; C. cascarilloides belongs to sect. Monguia; C. mangelong, C. kongensis, C. laevigatus and C. laniflorus belong to sect. Argyrocroton; C. lauioides, C. howii and C. damayeshu belong to sect. Adenophylli. The remaining Chinese Croton species might be placed into sect. Croton. A key for Chinese Croton species based on trichome morphology is provided.DOI: http://dx.doi.org/10.3329/bjpt.v20i1.15468Bangladesh J. Plant Taxon. 20(1): 85-94, 2013 (June)

Vegetative anatomy and micromorphology of Salvia divinorum (Lamiaceae) from Mexico, combined with chromatographic analysis of salvinorin A

Salvia divinorum--a species traditionally cultivated in Oaxaca, Mexico--possesses hallucinogenic properties. It is legally recognized as a controlled substance and prohibited in many countries. The proper identification of the plant, both in fresh and dried forms, is an important issue in crime-prevention campaigns. This paper provides a thorough anatomical description of leaves, petioles, and stems of S. divinorum. Detailed investigation of foliar trichomes was performed and illustrated. In addition, chromatographic analyses, including TLC and HPLC, were applied to fresh and dried plant material, together with the standard reference salvinorin A. A comprehensive identification method for S. divinorum based on a thorough anatomical examination is proposed, combined with chemical analysis for proper plant recognition.

Ambient Variable Pressure Field Emission Scanning Electron Microscopy for Trichome Profiling of Plectranthus tomentosa by Secondary Electron Imaging

Glandular and nonglandular trichomes on the leaf surface of Plectranthus tomentosa were investigated by variable pressure field emission scanning electron microscopy (VP-FESEM). The segments of the plant's leaves were directly mounted without any specimen preparation, and examined at ambient temperature using a variable pressure secondary electron (SE) detector under ca. 15 Pa. Foliar trichomes maintained their shapes and structures without severe surface collapse or charging. The adaxial leaf surface was abundantly covered with different types of trichome. Nonglandular trichomes consisted of a basal cell and a long (up to ca. <TEX>$300{\mu}m$</TEX>) stalk. Meanwhile, capitate glandular trichomes had a secretory head and a short or long stalk. Peltate glandular trichomes with globose secretory heads were observed in close contact with the leaf epidermis. Spherical projections on the secretory head showed the secretion process of glandular trichomes. In addition to the trichomes, oval stomata were distributed on the abaxial leaf surface. These results suggest that ambient VP-FESEM can be used to classify the dehydration-sensitive foliar trichomes of succulent plants by SE imaging. At the FESEM resolution, this approach facilitates the rapid and detailed morphological analysis of a variety of trichomes in diverse plant taxa with reduced labor and preparation.

English

The leaf anatomy and distribution of types of foliar trichome of four Heliotropium L. species have been investigated. The aim of this study is to evaluate the systematicrelevance of their diversity compared to the recent findings of systematic relationshipswithin the genus. The results of leaf anatomy patterns, especially venation, vascularsystem, various types of foliar trichome and localization of crystals are surprisingly of high systematic value and proof. Key words: Heliotropium L., leaf anatomy, Kranze-cells, C3 and C4 plants, venation, stomata, trichomes, crystals.

Foliar anatomy of Cynoglossum L. (Boraginaceae) from north Anatolia, Turkey

Bracts, basal and cauline leaves of North Anatolian representatives of Cynoglossum, viz., C. creticum Miller, C. officinale L., C. montanum L. and C. glochidiatum Wall. were investigated anatomically. Foliar thickness, trichome length and types, stomata types, stomata index, the presence of collenchyma and sclerenchyma were found to be important for delimitation of Cynoglossum species. All examined species have isobilateral leaf. Stomata were anisocytic and anomocytic. All the studied species had trichomes. Simple long and short trichomes were seen in leaves of C. creticum. Long and short trichomes with cystoliths at the base were seen in all leaves of C. montanum. Unicellular and multicellular unbranched trichomes and glandular trichomes were found in leaves of C. officinale. Short and adpressed trichomes were seen in leaves of C. glochidiatum.&#x0D;