Explore the vast range of titles available.

The digestive organs of carnivorous plants have external (abaxial) glands and trichomes, which perform various functions. Dionaea muscipula Ellis (the Venus flytrap) is a model carnivorous plant species whose traps are covered by external trichomes. The aim of the study was to fill in the gap regarding the structure of the stellate outer trichomes and their immunocytochemistry and to determine whether these data support the suggestions of other authors about the roles of these trichomes. Light and electron microscopy was used to show the trichomes’ structure. Fluorescence microscopy was used to locate the carbohydrate epitopes that are associated with the major cell wall polysaccharides and glycoproteins. The endodermal cells and internal head cells of the trichomes were differentiated as transfer cells, and this supports the idea that stellate trichomes transport solutes and are not only tomentose-like trichomes. Trichome cells differ in the composition of their cell walls, e.g., the cell walls of the internal head cells are enriched with arabinogalactan proteins (AGPs). The cell walls of the outer head cells are poor in both low and highly homogalacturonans (HGs), but the immature trichomes are rich in the pectic polysaccharide (1–4)–β-D-galactan. In the immature traps, young stellate trichomes produce mucilage which may protect the trap surface, and in particular, the trap entrance. However, the role of these trichomes is different when the outer head cells collapse. In the internal head cells, a thick secondary wall cell was deposited, which together with the thick cell walls of the outer head cells played the role of a large apoplastic space. This may suggest that mature stellate trichomes might function as hydathodes, but this should be experimentally proven.

Nepenthes L. species (tropical pitcher plants) are a classic example of carnivorous plants. The Nepenthes traps are highly specialized pitchers with a zoned structure. On the outer surface of the pitcher, there are nectaries and various types of trichomes, including glandular trichomes. The main aim of our study was to examine these glandular trichome structures and check the distribution of the homogalacturonans (HGs) and hemicelluloses in the cell wall of trichome cells. The structure of Nepenthes bicalcarata Hook. f. and Nepenthes albomarginata T.Lobb ex Lindl. trichomes was analyzed using light and electron microscopy. The antibodies were used against the wall components [anti-pectic homogalacturonans (HGs): JIM5 (low methylesterified HGs), LM19 (low methylesterified HGs), CCRC-M38 (a fully de-esterified HGs), JIM7 (highly esterified HGs), LM20 (esterified HGs), LM5 (galactan) and anti-hemicelluloses: LM25 (xyloglucan), LM15 (galactoxyloglucan), CCRC-M138 (xylan), and LM10 antibody (xylan)]. The localization of the examined compounds was determined using immunohistochemistry techniques. The presence of endodermal and transfer cells supports the idea that peltate trichomes actively transport solutes. Also, the presence of pectic homogalacturonans and hydrophilic hemicelluloses indicates that water or aqueous solutions are transported through the trichomes’ cell walls. Our study supports the idea that these trichomes may act as hydathodes or hydropotes.

This study presents the first comparative analysis of the leaf secretory structures across Asteraceae. In this work, the leaf secretory structures of more than 500 species of 35 of the 40 tribes and 11 of the 13 subfamilies of Asteraceae are described and compared to evaluate their diversity at the tribe level and to identify evolutionary patterns. Leaf secretory structures are present in 28 of the 35 analyzed tribes and correspond to canals (recorded in 17 tribes), secretory cavities (1 tribe), hydathodes (19 tribes), laticifers (4 tribes) and glandular trichomes (24 tribes). Canals are mostly associated with vascular bundles and predominate in Asteroideae, while cavities were only present within Tageteae. Hydathodes occur in leaves without divisions and with well-developed teeth. Laticifers were observed only in the tribes of Cichorioideae. Seven glandular trichome morphotypes were differentiated by their cellular composition and shape. These observations together with the available information showed that secretory structures are found in 80% of the Asteraceae tribes. Four of the 40 tribes did not present any type of secretory structure. Our study reveals that almost all of the tribes possess one to three types of secretory structures, and are absent in some early-diverging clades. Character evolution analyses show that glandular trichomes are plesiomorphic in Asteraceae. This study found that secretory structures prevail in late-diverging lineages and were taxonomically informative at different levels. Our comparative study of the secretory structures in Asteraceae is essential for the standardization of its terminology and will provide a frame of reference for future studies.

Leaf teeth, i.e. projections of the leaf margin, are common among angiosperms. These structures may differ in several aspects, e.g. in the presence or absence of an associated gland. Cucurbitoid teeth, which have an associated gland, have been reported to species of Datiscaceae, Begoniaceae and Cucurbitaceae, all from order Cucurbitales. However, no structural characterization has ever been made to confirm the nature of such associated gland in species of Cucurbitaceae; rather, studies so far have merely reported the occurrence of guttation. We aimed to anatomically characterize and identify the nature of glands associated with cucurbitoid teeth in Cucurbitaceae species. Margin samples of leaves at different developmental stages were obtained from seven Cucurbitaceae species, fixed in FAA and processed following usual procedures in optical and scanning electron microscopies. Saplings of Cucumis sativus were placed in a humidity chamber to induce guttation for ulterior chemical characterization of the exudate. Hydathodes were confirmed to occur in all studied species. Their structure consists of an uniseriate epidermis with water pores, reduced epithem, absent sheath and terminal vascularization being formed exclusively by xylem. The presence of sugars in the exudate, which could lead to mistaking hydathodes for nectaries, was ruled out by glucose strip tests. We have characterized, for the first time, the structure of hydathodes in the Cucurbitaceae, thereby elucidating the structure of the glands associated with cucurbitoid teeth. Investigating tooth structure in the Begoniaceae and Datiscaceae should contribute to better knowing the order through taxonomic and biological perspectives.

Xanthomonas campestris pv. campestris (Xcc) is a seed‐transmitted vascular pathogen causing black rot disease on cultivated and wild Brassicaceae. Xcc enters the plant tissues preferentially via hydathodes, which are organs localized at leaf margins. To decipher both physiological and virulence strategies deployed by Xcc during early stages of infection, the transcriptomic profile of Xcc was analysed 3 days after entry into cauliflower hydathodes. Despite the absence of visible plant tissue alterations and despite a biotrophic lifestyle, 18% of Xcc genes were differentially expressed, including a striking repression of chemotaxis and motility functions. The Xcc full repertoire of virulence factors had not yet been activated but the expression of the HrpG regulon composed of 95 genes, including genes coding for the type III secretion machinery important for suppression of plant immunity, was induced. The expression of genes involved in metabolic adaptations such as catabolism of plant compounds, transport functions, sulphur and phosphate metabolism was upregulated while limited stress responses were observed 3 days postinfection. We confirmed experimentally that high‐affinity phosphate transport is needed for bacterial fitness inside hydathodes. This analysis provides information about the nutritional and stress status of bacteria during the early biotrophic infection stages and helps to decipher the adaptive strategy of Xcc to the hydathode environment. In planta transcriptomic analysis of Xanthomonas campestris inside cauliflower hydathodes reveals the adaptative processes at play during early infection.

Root hemiparasites from the rhinanthoid clade of Orobanchaceae possess metabolically active glandular trichomes that have been suggested to function as hydathode trichomes actively secreting water, a process that may facilitate resource acquisition from the host plant's root xylem. However, no direct evidence relating the trichomes to water secretion exists, and carbon budgets associated with this energy-demanding process have not been determined. Macro- and microscopic observations of the leaves of hemiparasitic Rhinanthus alectorolophus were conducted and night-time gas exchange was measured. Correlations were examined among the intensity of guttation, respiration and transpiration, and analysis of these correlations allowed the carbon budget of the trichome activity to be quantified. We examined the intensity of guttation, respiration and transpiration, correlations among which indicate active water secretion. Guttation was observed on the leaves of 50 % of the young, non-flowering plants that were examined, and microscopic observations revealed water secretion from the glandular trichomes present on the abaxial leaf side. Night-time rates of respiration and transpiration and the presence of guttation drops were positively correlated, which is a clear indicator of hydathode trichome activity. Subsequent physiological measurements on older, flowering plants indicated neither intense guttation nor the presence of correlations, which suggests that the peak activity of hydathodes is in the juvenile stage. This study provides the first unequivocal evidence for the physiological role of the hydathode trichomes in active water secretion in the rhinanthoid Orobanchaceae. Depending on the concentration of organic elements calculated to be in the host xylem sap, the direct effect of water secretion on carbon balance ranges from close to neutral to positive. However, it is likely to be positive in the xylem-only feeding holoparasites of the genus Lathraea, which is closely related to Rhinanthus. Thus, water secretion by the hydathodes might be viewed as a physiological pre-adaptation in the evolution of holoparasitism in the rhinanthoid lineage of Orobanchaceae.

A taxonomic treatment for the 17 species of Elaphoglossum sect. Setosa found in Brazil is presented. The species of this section are recognized by the presence of subulate scales and hydathodes on adult leaves, or if hydathodes apparently absent, the leaves less than 10 cm long and spathulate. Several species are also characterized by the presence of minute glandular hairs on petioles and laminae. In Brazil, the group is most diverse in the mountains of southeastern Brazil, where the species grow in a variety of habitats, from deeply shaded riverbeds to partially sunny road banks. Elaphoglossum boragineum, E. brachyneuron, E. eximium and E. hieracioides are first records for the country, some of these known from only one or two collections made on mountains in northern Brazil. Additionally, misapplied names that have long been used in the literature and herbarium specimens, such as E. aubertii, E. jamesonii, E. plumieri, E. spatulatum, and villosum are here excluded from the Brazilian flora. We provide identification keys, descriptions, synonyms, comments, line drawings, spore images, distribution maps, and an index of herbarium vouchers to all species accepted in this treatment. Lectotypes are designated for Acrostichum alpestre, A. boragineum, and A. tenellum. A neotype is designated for A. horridulum.

The taxonomy of neotropical Salicaceae, a family that now includes the majority of the former Flacourtiaceae, has been problematic, especially because they display very diverse morphology and have several characteristics in common with many other families. Recent phylogenetic studies have proposed substantial changes at both family and generic levels. Considering the importance of anatomy as an aid for taxonomy, the gathering of anatomical data for the family is fundamental to help clarify the taxonomic problems. Leaves belonging to Abatia americana (four samples), Banara brasiliensis (2), Casearia arborea (4), C. decandra (5), C. gossypiosperma (2), C. obliqua (1), C. sylvestris (3), C. ulmifolia (3), Prockia crucis (3), and Xylosma prockia (4) and the closely related Carpotroche brasiliensis (3) from Achariaceae, were studied by standard microscopy techniques. The leaves were anatomically described, emphasizing their differences and similarities. Similar characters for the neotropical Salicaceae (former Flacourtiaceae) and Salicaceae strictu sensu were recognized, such as the presence of salicoid leaf teeth, brachyparacytic stomata, secondary growth of the petiole, abundance of crystals, collateral and arch-shaped vascular system at the midrib, and sclerenchyma accompanying the bundles. These data demonstrate that leaf anatomy can provide evidence to assist with the taxonomy of Salicaceae, at family, generic, and specific levels.

Guttation is one of the most conspicuous visible phenomena in plants occurring in a wide range of plants. The guttation fluids, though look clear and translucent, carry a number of organic and inorganic constituents. The organic component may include sugars, amino acids, general proteins, antimicrobial phylloplane proteins, transport proteins for transporting sucrose, purine and cytokinins, toxic elements etc. and enzymes such as peroxidases, dehydrogenases, ATPases, in addition to mRNA, ATP, reductants and other important ingredients of plant life. Guttation fluids also contain a number of natural plant hormones such as auxins, gibberellins, cytokinins, abscisic acid etc., apart from several vitamins. Recent discoveries have revealed the presence of a number of salts, ions, nutrients and macromolecules in guttation fluid playing significant role in enhancing disease resistance, tolerance to toxic elements, photosynthetic efficiency, biomass production and economic yield of agricultural crops. In the light of aforementioned discoveries in guttation transgenic plants have been created to serve as bio-factories for producing various kinds of phytochemicals of immense agricultural, pharmaceutical, nutriceutical, therapeutic, cosmeceutic and commercial significance impacting food productivity and human health adding happiness to life.