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Pollination of Utricularia vulgaris. a–c Behaviour of Eristalis tenax on U. vulgaris flowers. d, e Pollen grains of U. vulgaris on the surface of Eristalis tenax; bar = 50 μm
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In Utricularia, the flower spur is a nectary and in this organ, nectar is produced and stored. This study aimed to examine the structure of the nectary trichomes in four Utricularia species (Utricularia vulgaris L., U. australis R.Br., U. bremii Heer and U. foliosa L.) from the generic section Utricularia. We have investigated whether species with...
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Pinguicula (Lentibulariaceae) is a genus comprising around 96 species of herbaceous, carnivorous plants, which are extremely diverse in flower size, colour and spur length and structure as well as pollination strategy. In Pinguicula, nectar is formed in the flower spur; however, there is a gap in the knowledge about the nectary trichome structure i...
Hesperis L. (Brassicaceae) is native to Europe, to Marocco, and to temperate and tropical Asia, but centered to the temperate zones of Eurasia. This genus comprises approximately 56 species, 49 of them occurring in Europe and 3 species occur in Austria: Hesperis tristis and H. sylvestris with glandular stem, and the eglandular species H. matronalis...
Citations
... In Lentibulariaceae (genera: Utricularia, Genlisea, and Pinguicula), the spur is treated as a nectary, and nectar is produced by glandular capitate trichomes [43][44][45][46]. However, some corolla glandular trichomes may produce volatile compounds [47,48]. ...
Central American and Mexican Pinguicula species are characterized by enormous divergence in size and color of flowers and are pollinated by butterflies, flies, bees, and hummingbirds. It is known that floral trichomes are key characters in plant-pollinator interaction. The main aim of our study was to verify our hypothesis that the distribution and diversity of non-glandular and glandular trichomes are related to the pollinator syndromes rather than the phylogenetic relationships. The studied sample consisted of Central American and Mexican species. In our study, we relied on light microscopy and scanning electron microscopy with a phylogenetic perspective based on ITS DNA sequences. The flower morphology of species pollinated by butterflies and hummingbirds was similar in contrast to species pollinated by flies and bees. Species pollinated by butterflies and hummingbirds contained low diversity of non-glandular trichomes, which occurred mostly in the tube and basal part of the spur. Surprisingly, in P. esseriana and P. mesophytica, non-glandular trichomes also occurred at the base of lower lip petals. In the case of species pollinated by flies/bees, we observed a high variety of non-glandular trichomes, which occurred on the surface of corolla petals, in the tube, and at the entrance to the spur. Furthermore, we did not identify any non-glandular trichomes in the spur. The capitate glandular trichomes were of similar morphology in all examined species. There were minor differences in the shape of the trichome head, as well as the length and the number of stalk cells. The distribution and the diversity of non-glandular and glandular trichomes and pollinator syndromes were mapped onto a phylogenetic reconstruction of the genus. Most micromorphological characters appear to be associated more with floral adaptation to pollinators and less with phylogeny.
... Trichomes perform a wide variety of specific functions [81]. Examples include the climbing hairs of Humulus lupulus (hop), sensitive hairs of Dionaea muscipula (Venus flytrap), or internal hairs of species of Utricularia (bladderwort), which are involved in various functions of the bladder-like trap (removing excess water, solute transport, and digestive activities [82]). ...
As organs of photosynthesis, leaves are of vital importance for plants and a source of inspiration for biomimetic developments. Leaves are composed of interconnected functional elements that evolved in concert under high selective pressure, directed toward strategies for improving productivity with limited resources. In this paper, selected basic components of the leaf are described together with biomimetic examples derived from them. The epidermis (the “skin” of leaves) protects the leaf from uncontrolled desiccation and carries functional surface structures such as wax crystals and hairs. The epidermis is pierced by micropore apparatuses, stomata, which allow for regulated gas exchange. Photosynthesis takes place in the internal leaf tissue, while the venation system supplies the leaf with water and nutrients and exports the products of photosynthesis. Identifying the selective forces as well as functional limitations of the single components requires understanding the leaf as an integrated system that was shaped by evolution to maximize carbon gain from limited resource availability. These economic aspects of leaf function manifest themselves as trade-off solutions. Biomimetics is expected to benefit from a more holistic perspective on adaptive strategies and functional contexts of leaf structures.
... Utricularia vulgaris forms an emergent racemose inflorescence with golden-yellow flowers on an erect flower scape 30-50 cm high under favourable conditions from June to September. Although flowers can be pollinated by dipterans (Płachno et al., 2018), U. vulgaris is one of three European Utricularia (with U. intermedia and U. minor) capable of self-pollination to form fertile fruit and viable seeds (Taylor, 1989;Fleischmann and Schlauer, 2014). Mature fruit are globose, 3-5 mm long, open by an upper lid and contain about 50-150 small (mean seed mass is 0.052 mg; L. Adamec, unpubl. ...
Generative reproduction of the carnivorous aquatic plant Utricularia vulgaris (Lentibulariaceae) from seeds may be a critical process in the recovery of natural populations following temporary drying of habitat, and in the colonisation of new potential sites through dispersal of seeds by water birds. However, little is presently known about the seed ecology and germination biology of this species. We tested the germination response of seeds under various temperature and seed storage regimes, to examine the processes required for seed dormancy alleviation and the effects of different germination solution and temperature on germination probability. Seeds likely possess non-deep simple morphophysiological dormancy alleviated by warm stratification. Highest germination success was recorded for warm-stratified seeds and seeds exposed to ethylene. Seeds were photophilous, with germination more successful at 21°C than at 25°C and greatest in slightly alkaline (pH 8) germination solution containing KHCO3, CaCl2 and MgSO4 mimicking the mesotrophic humic waters in which the species naturally occurs. In the alkaline solution, 97% of seeds rose to the surface prior to germination. In natural habitats, this effect may facilitate seedlings reaching the warmer and irradiated water surface. As seed germination success appears linked to light availability, water chemistry, and seed position in the water column, careful management and ecological restoration of remnant habitats harbouring this species may need to ensure positive conservation outcomes.
... Trichomes in flowers might play structural roles during flower synorganization (El Ottra et al., 2013;Tan et al., 2016), promote toxin synthesis, and act as active mechano-sensory switches and wave detectors during herbivory (Zhou et al., 2016;Liu et al., 2017). Floral trichomes also play key mechanical and biochemical functions in various pollination syndromes (Young et al., 1984;Cropper and Calder, 1990;Cocucci, 1991;Hu et al., 2008;Martins et al., 2013;Boff et al., 2015;Płachno et al., 2018Płachno et al., , 2019Stpiczyńska et al., 2018). For instance, trichomes inside the Aristolochia (Aristolochiaceae) perianth are specialized either as mechanical structures to temporarily trap insects, or as secretory trichomes to feed them (Dafni, 1984;Oelschlägel et al., 2009;Pabón-Mora et al., 2015;Erbar et al., 2016;Suárez-Baron et al., 2019). ...
Background and Aims
The epidermis constitutes the outermost tissue of the plant body. Although it plays major structural, physiological, and ecological roles in embryophytes, the molecular mechanisms controlling epidermal cell fate, differentiation, and trichome development is scarce across angiosperms, and almost unexplored in floral organs.
Methods
In this study, we assess the spatio-temporal expression patterns of GL2, GL3, TTG1, TRY, MYB5, MYB6, HDG2, MYB106-like, WIN1, and RAV1-like homologs in the magnoliid Aristolochia fimbriata (Aristolochiaceae) by using comparative RNA-seq and in situ hybridization assays.
Key Results
Genes involved in A. fimbriata trichome development vary depending on the organ where they are formed. Stem, leaf and pedicel trichomes recruit most of the transcription factors (TFs) described above. Conversely, floral trichomes only use a small subset of genes including AfimGL2, AfimRAV1-like, AfimWIN1, AfimMYB106-like, and AfimHDG2. The remaining TFs AfimTTG1, AfimGL3, AfimTRY, AfimMYB5, and AfimMYB6 are restricted to the abaxial (outer) and the adaxial (inner) pavement epidermal cells.
Conclusions
We re-evaluate the core genetic network shaping trichome fate in flowers of an early-divergent angiosperm lineage and show a morphologically diverse output with a simpler genetic mechanism in place when compared to the models Arabidopsis thaliana and Cucumis sativus. In turn, our results strongly suggest that the canonical trichome gene expression appears to be more conserved in vegetative than in floral tissues accross angiosperms.
... In the merocrine model, nectar metabolites are packaged into vesicles that fuse with the plasma membrane, releasing the nectar components. The role of the merocrine-based secretion in cotton nectaries is best supported when one considers the ultrastructural analyses which illustrate shared structural components among the four nectary types of cotton, similar to the trichomatic nectaries reported in other taxa, such as Abutilon (Kronestedt et al., 1986), Hibiscus (Sawidis et al., 1987, Platanthera (Stpiczy nska et al., 2005), and Utricularia (Plachno et al., 2018). Specifically, the prominence of rough endoplasmic reticulum positioned parallel to the cell walls may contribute to vesicle trafficking (Eleftheriou and Hall, 1983a), and there is an abundance of such vesicles fusing to plasma membranes within the nectariferous parenchyma and throughout the papillae of cotton nectaries. ...
Nectar is a primary reward mediating plant-animal mutualisms to improve plant fitness and reproductive success. Four distinct trichomatic nectaries develop in cotton (Gossypium hirsutum), one floral and three extrafloral, and the nectars they secrete serve different purposes. Floral nectar attracts bees for promoting pollination, while extrafloral nectar attracts predatory insects as a means of indirect protection from herbivores. Cotton therefore provides an ideal system for contrasting mechanisms of nectar production and nectar composition between different nectary types. Here, we report the transcriptome and ultrastructure of the four cotton nectary types throughout development and compare these with the metabolomes of secreted nectars. Integration of these datasets supports specialization among nectary types to fulfill their ecological niche, while conserving parallel coordination of the merocrine-based and eccrine-based models of nectar biosynthesis. Nectary ultrastructures indicate an abundance of rough endoplasmic reticulum positioned parallel to the cell walls and a profusion of vesicles fusing to the plasma membranes, supporting the merocrine model of nectar biosynthesis. The eccrine-based model of nectar biosynthesis is supported by global transcriptomics data, which indicate a progression from starch biosynthesis to starch degradation and sucrose biosynthesis and secretion. Moreover, our nectary global transcriptomics data provide evidence for novel metabolic processes supporting de novo biosynthesis of amino acids secreted in trace quantities in nectars. Collectively, these data demonstrate the conservation of nectar-producing models among trichomatic and extrafloral nectaries.
... Our data show that there is a large amount of starch before nectar secretion in petals of X. aromatica, which subsequently declines due to its hydrolysis concurrent with the release of nectar, as recorded for most floral nectaries already studied (Fahn 1988;Nepi et al. 2011;Płachno et al. 2018). ...
Secretory structures that produce floral rewards have been rarely reported for Annonaceae. We identified a glandular region in Xylopia aromatica, which consisted of a nectary and an elaiophore. This study aimed to describe the structure and secretory process of these glandular structures, highly correlated to the reproductive biology of this species. Anatomical and ultrastructural studies were performed prior to and during anthesis, focusing on the channel and pollination chamber. The floral nectary is placed in the roof of the chamber. It has a secretory epidermis and subglandular parenchyma and is immediately contiguous with the elaiophore, a portion that delimits the pollination channel and produces lipids. The release of nectar begins in the pistillate phase, while the elaiophore starts secreting prior to anthesis, both of which finishing during the staminate phase. Lipids form a sticky layer covering the channel surface, which provides access to the chamber. The cell machinery of the epidermis for both, nectary and elaiophore, is highly correlated with the exudates, despite their high structural similarity. Nectar attracts pollinators to the pollination chamber, while lipids seem to act in pollen adhesion to the body of pollinators. Both of exudates appear to act in complementary ways during pollination.
... Although edible trichomes may act as a reward in addition to nectar, a detailed study of nectar production and secretion in Pinguicula is required to be absolutely certain that all Pinguicula species produce nectar and in what quantities. In the related genera Utricularia (Hobbhahn et al., 2006;Clivati et al., 2014;Płachno et al., 2017Płachno et al., , 2018Płachno et al., , 2019a and Genlisea (Aranguren et al. 2018), the reward for pollinators is nectar. However, in some species (U. antennifera, U. capilliflora, U. dunlopii, U. dunstaniae and U. lowriei), the spur is significantly reduced and the corolla forms filiform appendages (Taylor, 1989;Reut and Jobson, 2010). ...
Background and aims:
Floral food bodies (including edible trichomes) are a form of floral reward for pollinators. This type of nutritive reward has been recorded in several angiosperm families: Annonaceae, Araceae, Calycanthaceae, Eupomatiaceae, Himantandraceae, Nymphaeaceae, Orchidaceae, Pandanaceae and Winteraceae. Although these bodies are very diverse in their structure, their cells contain food material: starch grains, protein bodies or lipid droplets. In Pinguicula flowers, there are numerous multicellular clavate trichomes. Previous authors have proposed that these trichomes in the Pinguicula flower play the role of "futterhaare" ("feeding hairs") and are eaten by pollinators. The main aim of this paper was to investigate whether the floral non-glandular trichomes of Pinguicula contain food reserves and thus are a reward for pollinators. The trichomes from the Pinguicula groups, which differ in their taxonomy (species from the subgenera: Temnoceras, Pinguicula, Isoloba) as well as the types of their pollinators (butterflies / flies and bees / hummingbirds), were examined. Thus, it was determined whether there are any connections between the occurrence of food trichomes and phylogeny position or pollination biology. Additionally, we determined the phylogenetic history of edible trichomes and pollinator evolution in the Pinguicula species.
Methods:
The species that were sampled were: Pinguicula moctezumae, P. esseriana, P. moranensis, P. emarginata, P. rectifolia, P. mesophytica, P. hemiepiphytica, P. agnata, P. albida, P. ibarrae, P. martinezii, P. filifolia, P. gigantea, P. lusitanica, P. alpina and P. vulgaris. Light microscopy, histochemistry, scanning and transmission electron microscopy were used to address our aims with a phylogenetic perspective based on matK/trnK DNA sequences.
Key results:
No accumulation of protein bodies or lipid droplets was recorded in the floral non-glandular trichomes of any of the analysed species. Starch grains occurred in the cells of the trichomes of the bee/fly-pollinated species: P. agnata, P. albida, P. ibarrae, P. martinezii, P. filifolia and P. gigantea but not in P. alpina or P. vulgaris. Moreover, starch grains were not recorded in the cells of the trichomes of the Pinguicula species that have long spurs, which are pollinated by Lepidoptera (P. moctezumae,P. esseriana, P. moranensis, P. emarginata, and P. rectifolia) or birds (P. mesophytica, P. hemiepihytica) or in species with a small and whitish corolla that self-pollinate (P. lusitanica). The results on the occurrence of edible trichomes and pollinator syndromes were mapped onto a phylogenetic reconstruction of the genus.
Conclusion:
Floral non-glandular trichomes play the role of edible trichomes in some Pinguicula species (P. agnata, P. albida, P. ibarrae, P. martinezii, P. filifolia and P. gigantea), which are mainly classified as bee-pollinated species that had originated from Central and South America. It seems that in the Pinguicula that are pollinated by other pollinator groups (Lepidoptera, hummingbirds), the non-glandular trichomes in the flowers play a role other than that of a floral reward for their pollinators. Edible trichomes are symplesiomorphic for the Pinguicula species, and thus do not support a monophyletic group such as a synapomorphy. Nevertheless, edible trichomes are derived and are possibly a specialisation for fly and bee pollinators by acting as a food reward for these visitors.
... A similar type of inclusions was observed in nectary vacuoles of various plants in the nectar secretion stage (e.g. Konarska 2011;Machado et al. 2017;Weryszko-Chmielewska and Chwil 2017;Płachno et al. 2018). Wist and Davis (2006) and Gaffal et al. (2007) have demonstrated that the formation of multiform inclusions in vacuoles is one of the initial signs of degenerative changes initiating the process of cell aging. ...
Floral nectaries are important components of floral architecture and significant taxonomic traits facilitating assessment of relationships between taxa and can contribute substantially to studies on the ecology and evolution of a particular genus. Knowledge of nectary structure and functioning allows better understanding of the mutualistic interactions between the pollinator and the plant. Robinia viscosa var. hartwigii (Hartweg’s locust), planted in many European countries as an ornamental plant and used for recovery of degraded areas and urban arborisation, is a valuable melliferous species often visited by honeybees and bumblebees. The aim of this study was to investigate the microstructure of the floral nectaries of R. viscosa var. hartwigii with the use of light, fluorescence, scanning, and transmission electron microscopes. The photosynthetic nectaries were located on the inner surface of the cup-like receptacle. The components of pre-nectar were synthesised in the chloroplasts of the glandular parenchyma and transported via the conducting elements of the phloem. Nectar was released through modified nectarostomata. Nectar secretion presumably proceeded in the eccrine mode, whereas nectar transport represented the symplastic and apoplastic types. The cuticle on the nectary epidermis surface contained lipids, essentials oils, and flavonoids, while proteins and flavonoids were present in the glandular parenchyma cells. Idioblasts containing phenolic compounds, tannins, and polysaccharides were observed between the glandular parenchyma cells. The location of the nectaries and the mode of nectar production in the flowers of the Hartweg’s locust follow the common location and structure pattern characteristic for the nectaries in some members of the subfamily Papilionoideae and can be a significant taxonomic trait for the genus Robinia and the tribe Robinieae.
... Suction traps of Utricularia function on the basis of actively formed negative pressure (e.g., Sasago and Sibaoka, 1985;Poppinga et al., 2016Poppinga et al., , 2018. As with all other (aquatic) Utricularia species, the traps contain five types of glands (hairs) the function of which is still partly unresolved (Lloyd, 1942;Juniper et al., 1989;Taylor, 1989;Poppinga et al., 2016Poppinga et al., , 2018Westermeier et al., 2017;Adamec, 2018a;Jobson et al., 2018;Płachno et al., 2018). The numerous and large quadrifid and bifid glands are crucial for trap physiology. ...
... The numerous and large quadrifid and bifid glands are crucial for trap physiology. The former glands secrete digestive enzymes serving prey digestion and, probably, also absorb released nutrients, while the latter glands pump the water out of the traps and form the negative pressure essential for prey capture (Sasago and Sibaoka, 1985;Adamec, 2018a;Poppinga et al., 2016Poppinga et al., , 2018Płachno et al., 2018). Regardless of the crucial role of the traps for prey capture and, thus, for plant ecophysiology, they can be used for reliable and quick determination of the three Utricularia species within the UI aggregate (Thor, 1988;Taylor, 1989;Kleinsteuber, 1996;Schlosser, 2003;Płachno and Adamec, 2007;Fleischmann and Schlauer, 2014). ...
... No specific information is available on the pollination mode in UI. However, on the basis of anatomical similarity of UI flowers with those of UO, US and U. vulgaris including the presence of nectar glands inside the flower spur and, particularly, of the finding of a pollinator fly and bee in U. vulgaris (Thor, 1988;Płachno et al., 2018), it is possible to consider that UI flowers are entomophilous and self-pollinating (autogamy). The pale green turions are hairy, spherical to ovoid and are 3−8 mm long. ...
Utricularia intermedia Hayne, U. ochroleuca R.W. Hartm., U. stygia Thor and U. bremii Heer ex Kölliker (Lentibulariaceae, Lamiales) are the four rarest and critically endangered European Utricularia (bladderwort) species from the generic section Utricularia. They are aquatic, submerged or amphibious carnivorous plants with suction traps which grow in very shallow, standing dystrophic (humic) waters such as pools in peat bogs and fens (also pools after peat or fen extraction), shores of peaty lakes and fishponds; U. bremii also grows in pools in old shallow sand-pits. These Utricularia species with boreal circumpolar distribution (except for U. bremii) are still commonly growing in northern parts of Europe (Scandinavia, Karelia) but their recent distribution in Central Europe is scarce to very rare following a marked population decline over the last 120 years. All species have very thin linear shoots with short narrow to filamentous leaves bearing carnivorous traps (bladders, utricles) 1-5 mm large. The first three species form distinctly dimorphic shoots differentiated into pale carnivorous ones bearing most or all traps, and green photosynthetic shoots with only a few (or without) traps, while the last species usually forms non-differentiated (monomorphic) or slightly differentiated shoots. The plants exhibit a marked physiological polarity along their linear shoots with rapid apical shoot growth. Their very high relative growth rate is in harmony with the record-high net photosynthetic rate of their photosynthetic shoots. Flowering of these species is common under favourable conditions and is stimulated by high temperatures but only U. intermedia sets seeds; the other species are sterile due to pollen malformation. Some molecular-taxonomic studies indicate that U. ochroleuca and U. stygia might be hybrids between U. intermedia and U. minor. All species propagate mainly vegetatively by regular branching and reach high relative growth rates under favourable conditions. All species form spherical dormant winter buds (turions). Suction traps actively form negative pressures of ca. -0.22 to -0.25 bar. The traps are physiologically very active organs with intensive metabolism: as a result of the presence of abundant glands inside the traps, which secrete digestive enzymes and absorb nutrients from captured prey carcasses (quadrifid glands) or take part in pumping water out of the traps and producing negative pressure (bifid glands), their aerobic respiration rate is ca. 2-3 times higher (per unit biomass) than that of leaves. Although oxygen concentrations inside reset traps are (almost) zero, traps are inhabited by many microscopic organisms (bacteria, euglens, algae, ciliates, rotifers, fungi). These commensal communities create a functional food web and in traps with captured macroscopic prey, they act as digestive mutualists and facilite prey digestion. Traps secrete a great amount of organic substances (sugars, organic acids, aminoacids) to support these commensals (‘gardening’). Yet the nutritional role of commensals in prey-free traps is still unclear. Quadrifid glands can also serve in the reliable determination of three species. Ecological requirements of U. intermedia, U. ochroleuca and U. stygia are very similar and include very shallow dystrophic waters (0-30 cm deep) with highly variable levels of dystrophy, common mild water level fluctuations, oligo-mesotrophic to slighly eutrophic waters, optimal pH values from 5.5-7.0 but always high free-CO2 concentrations of 0.8-1.5 mM. Limited data indicate that U. bremii is partly a stenotopic species preferring only slightly acidic to neutral (pH 6-7), very soft to slightly hard, oligo-mesotrophic waters. Yet it can grow well both in strongly dystrophic and clear waters, in peat bogs as well as sand-pits over peaty soil and clayish sand. Long-term, very low water levels in combination with habitat eutrophication, whatever the reason, leading to peat bog and fen infilling, are the most common and unfavourable ecological threads at the most sites of the four rare Utricularia species. However, ecological consequences of high-water level at the sites can be ambiguous for the populations: it reduces the strongly competitive cyperoid and graminoid species but can speed up site eutrophication. All four species are considered (critically) threatened in European countries and are usually under official species protection or their sites are protected. Regeneration of infilled fens or peat bogs and creation of shallow fen pools and canals in these mires, combined with (re)-introductions of these species have shown to be a very successful and efficient measure to protect the natural populations for many decades. Old shallow sand-pit pools have become outstanding substitution habitats for the protection of U. bremii.
... In both genera, there are collateral vascular bundles in the nectaries (spurs). Papillose surfaces of the internal spur epidermis occur in the spurs of all Lentibulariaceae genera (Utricularia- Clivati et al. 2014;Płachno et al. 2016Płachno et al. , 2017Płachno et al. , 2018Genlisea-Aranguren et al. 2018). However, there is variability in the case of the occurrence of cuticular striations among the species. ...
... Similar nectary capitate trichomes, as are described here, have been recorded in the spurs of various Utricularia species (Farooq 1963;Farooq and Siddiqui 1966;Clivati et al. 2014;Płachno et al. 2016Płachno et al. , 2017Płachno et al. , 2018Płachno et al. , 2019b and Genlisea violacea (Aranguren et al. 2018). Unfortunately, there are no published data about the ultrastructure of the nectary trichomes in Genlisea. ...
... A similar accumulation of lipids was recorded in the pedestal cells of trichomes of Utricularia turions , and therefore, the occurrence of lipid droplets in the pedestal cells might not be directly connected with the secretion of nectar. Płachno et al. (2018Płachno et al. ( , 2019c proposed that the nectar secretion in Utricularia occurs via an eccrine mode. This type of nectar secretion probably occurs in P. esseriana due to its well-developed cell wall ingrowths. ...
Pinguicula (Lentibulariaceae) is a genus comprising around 96 species of herbaceous, carnivorous plants, which are extremely diverse in flower size, colour and spur length and structure as well as pollination strategy. In Pinguicula, nectar is formed in the flower spur; however, there is a gap in the knowledge about the nectary trichome structure in this genus. Our aim was to compare the nectary trichome structure of various Pinguicula species in order to determine whether there are any differences among the species in this genus. The taxa that were sampled were Pinguicula moctezumae, P. moranensis, P. rectifolia, P. emarginata and P. esseriana. We used light microscopy, histochemistry, scanning and transmission electron microscopy to address those aims. We show a conservative nectary trichome structure and spur anatomy in various Mexican Pinguicula species. The gross structural similarities between the examined species were the spur anatomy, the occurrence of papillae, the architecture of the nectary trichomes and the ultrastructure characters of the trichome cells. However, there were some differences in the spur length, the size of spur trichomes, the occurrence of starch grains in the spur parenchyma and the occurrence of cell wall ingrowths in the terminal cells of the nectary trichomes. Similar nectary capitate trichomes, as are described here, were recorded in the spurs of species from other Lentibulariaceae genera. There are many ultrastructural similarities between the cells of nectary trichomes in Pinguicula and Utricularia.
