Secretory Epidermis Research Articles

Morphoanatomy and evolution of the bracteole and sepal glands of the Amazonian genus Lophanthera A. Juss. (Galphimioid clade)

Abstract The presence of diverse secretory structures is emblematic of Malpighiaceae, such as the presence of nectaries secreting sugary nectar and elaiophores secreting oil-resin. Recent studies have demonstrated the morphoanatomical and chemical similarities between these two glands but, in general, there are no comparative morphoanatomical analysis on inflorescence glands. The Galphimioid clade is an excellent model for studies on the presence of secretory tissue due to the variation found among genera with regards to both their bracteole and sepal glands. In this work, we describe the morphoanatomy and histochemistry of bracteole and sepal glands in species of Lophanthera. Furthermore, we update the species geographic distribution map and explore the morphological diversity of both sepal and bracteole glands in the Neotropical Galphimioid clade. Samples collected in the field and obtained from herbarium specimens were processed under usual anatomical techniques. The bracteole glands varied in surface shape, while the calyx glands varied mainly in size. Anatomically, both types of gland have palisade secretory epidermis and vascularized secretory parenchyma. The presence of proteins, polysaccharides, phenolic compounds, and reducing sugar was detected by histochemical tests. The bracteole glands of the inflorescences in Lophanthera were characterized as nectaries that produce a hydrophilic secretion. The sepal glands were identified as elaiophores by the presence of lipids and fixed oil. The results reinforce the functional role of floral nectaries of bracteoles and elaiophores of sepals according to the nature of the secretion, its potential visitors, and reported literature. The morphofunctional diversity reported in this work is unprecedented for the clade and is fundamental in the adaptive evolution of the family.

Morphoanatomy, histochemical and secretions process of extrafloral nectaries in Joannesia princeps Vell. (Euphorbiaceae)

Joannesia princeps presents two acropetiolar glands, with topography and morphology similar to extrafloral nectaries (EFNs). In the present study we described the anatomy and the ultrastructure of acropetiolar glands, and analyzed the histochemistry and chemical composition of secretion in order to (i) verify if these glands are nectaries and (ii) understand the complexity of secretion and the cell compartment involved with the production and exudation. The samples were processed according to the standard methodology for anatomical and ultrastructural studies. The gland has uniseriate epidermis composed by palisade secretory cells. The secretion produced by the secretory epidermis is accumulated in a subcuticular space, which causes distention of the cuticle until it be broken, allowing the exudation. Xylem and phloem vascularize the gland, with the phloem reaching the nectariferous parenchyma, even close to the secretory epidermis. The histochemical tests revealed polysaccharides, mucilage and protein in the secretion, whereas the exudate chemical analysis showed that glucose, fructose and sucrose are components of the nectar, being fructose the sugar predominant. The secretion is complex and different organelles are involved in this synthesis and secretion process. Secretory parenchyma cells presented a large peripheral nucleus, vacuole with granular material, conspicuous endoplasmic reticulum, numerous mitochondria, plastids, and plasmodesmata. During the secretion process, a granular material is accumulated into the vacuole, which merges with the plasma membrane of the secretory epidermis, releasing this material into the periplasmatic spaces. After crossing the cell wall of the epidermal cell, the secretion is accumulated in a subcuticular space, until ready to be released by the cuticle disruption. Based on this study, we can affirm that the glands of it are extrafloral nectaries.

Diversity of staminal nectariferous appendages in disymmetric and zygomorphic flowers of Fumarioideae (Papaveraceae).

Staminal nectaries show diversity in their position, size, shape, color, and number in Ranunculales. In Papaveraceae, nectaries only appear at the base of stamen in these lineages with disymmetric and zygomorphic flowers. However, the diversity of the staminal nectaries' developmental characteristics and structure is unknown. The diversity of staminal nectaries of Hypecoum erectum, Ichtyoselmis macrantha, Adlumia asiatica, Dactylicapnos torulosa, Corydalis edulis, and Fumaria officinalis (six species belonging to six genera, respectively) in the Fumarioideae was investigated under scanning electron microscopy, light microscopy, and transmission electron microscopy. In all species studied, according to the developmental characteristics of the nectaries, four developmental stages can be divided into initiation, enlargement, differentiation, and maturation, and the number of nectaries can be determined at the stage of initiation (stage 1), and morphological differentiation occurs at the developmental stage 3. The staminal nectaries consist of secretory epidermis, parenchyma tissue, and phloem with some sieve tube elements reaching the secretory parenchyma cells; however, the number of cell layers of parenchyma can vary from 30 to 40 in I. macrantha and D. torulosa, to only 5 to 10 like in F. officinalis. Secretory epidermis cells are larger than secretory parenchyma cells with abundant microchannels on the outer cell wall. There were abundant mitochondria, Golgi bodies, rough endoplasmic reticulum, and plastids in secretory parenchyma cells. Nectar is stored in the intercellular space and exuded to the exterior via microchannels. In A. asiatica, according to the evidence of small secretory cell characteristics such as dense cytoplasm, and numerous mitochondria, together with the filamentous secretions present on the surface of epidermal cells on groove, it can be inferred that the U-shaped sulcate which is located in the white projection formed at the filament of triplets in A. asiatica is nectariferous.

How do fertile stamens and staminodes go differently in Kingdonia uniflora? Evidence from stamen numbers, ontogeny, and structure

Kingdonia uniflora is in Circaeasteraceae and has fertile stamens and staminodes which are both variable in number; however, the differentiating process of these two types of stamens and the nectariferous structure of staminodes are still unclear. Variation in number and ontogeny (including the degeneration stage of staminodes) of stamens in K. uniflora are investigated under SEM, TEM and LM. The results indicate that there are 63 floral formulas in 80 flowers counted, and the most frequent flower floral formula (4 flowers) is P5A°11A5G6. The correlation between the stamen number and the total floral organ number is high (0.61), while the highest correlation with the total number of floral organs is the number of carpels, and there is a weak correlation between the two types of stamens (-0.23). The stamen development period is divided into five stages, with differentiation of stamens occurring at stage 2. The anther wall formation of fertile stamens is of the basic type, and the simultaneous meiosis form tetrahedral tetrads, while mature pollens are 2-celled and tricolpate. Sporogenous tissue of staminodes fails to develop further at an earlier stage, without the formation of secondary sporogenous cells. The head of mature staminodes has nectary tissue consisting of the secretory epidermis (two types of secretory cells), nectary parenchyma (about 15 layers) and vascular tissue with vessel and sieve tube elements. There are well-developed microchannels in epidermal cell walls, and the cells related to secreting nectar are rich in mitochondria, endoplasmic reticula and small vesicles. In addition, microsporogenesis, male gametophyte development, the secretory function of staminodes, and other characteristics in K. uniflora are similar to those in Ranunculaceae. This study clarifies the differentiating stage of fertile stamens and staminodes and explores the new structure (nectary) that staminodes formed, and also, it enriched the secretion modes in Ranunculales.

Coryanthes macrantha (Orchidaceae: Stanhopeinae) and their floral and extrafloral secretory structures: an anatomical and phytochemical approach.

Coryanthes is one of the most fascinating genera of Stanhopeinae (Orchidaceae) because of its complex pollination mechanism and the peculiar structures of its flowers. Although Coryanthes macrantha is widely studied, investigation of the secretory structures and floral biology is important to understand the mechanisms and ecology of pollination, which deserve attention despite the difficulties of collecting fertile material in nature. We conducted a morpho-anatomical analysis of the floral and extrafloral secretory structures of C. macrantha to better understand the secretory structures, contribute to the knowledge of its floral biology and/or pollination processes and understand the ecological function of these structures. The analysis revealed that C. macrantha has epidermal osmophores with unicellular papillae that were foraged by male Eulaema bees, floral nectaries in the sepals and extrafloral nectaries in the bracts. In both the floral and extrafloral nectaries, the nectar is exuded by the stomata. Azteca ants foraged the bract and sepal nectaries in pre-anthesis and post-anthesis. We also described the secretory epidermis of pleuridia, and the mode of secretion of osmophores and nectaries and found that they attract specific foraging agents.

Are the spurs more complex than other petal types in Epimedium? Evidence from development, micromorphology, and nectary structure

• Concavities deepen in the development of petals leading to their different shapes. • Three special types of epidermis cells are observed in spurred petals. • Petal development depends on both cell division and anisotropic expansion. • Spurred petals are more complex than others with 6 epidermal cell types and 10–16 vascular bundles. As important organs attracting pollinators, spurs are the tubular outgrowths of flowers with rich diversities in color, shape, and size, and can increase reproductive success. The spurred petals in Epimedium L. (Berberidaceae) have diverse shapes and lengths, and others such as flat, shallow pockets, or saccate structures can also be found. Different shapes of petals may mean different features and functions, but research on petal development and structure is lacking in this genus hindering further research. Here, the petal development, micromorphology, and nectary structures of 9 species in Epimedium are observed to clarify the petal diversity. The results indicate that petal development can be divided into 5 stages, a concavity occur at different positions and then deepens in varying degrees during stage 4, which leads to petal differentiation. Petal stereoscopic structures were influenced by both cell division and anisotropic expansion in early developmental stages, the latter contributed greatly to spur elongation. There are 7 types of cells observed in Epimedium , with only 1 type of secretory cell; tabular fusiform cells appear in all 9 species; conical cells are widely distributed on the petals with nectaries, while papillose conical cells are only observed in spurs. Nectaries are usually distributed at the tip of the petal stereoscopic structure, consisting of the secretory epidermis, 2 to 13 layers of secretory parenchyma cells, and vascular tissues. These results help us to understand the morphogenesis and development of Epimedium , and provide morphological evidence for future studies on the phylogeny and evolution within the genus.

The diversity of elaborate petals in Isopyreae (Ranunculaceae): a special focus on nectary structure.

Elaborate petals are highly diverse in morphology, structure, and epidermal differentiation and play a key role in attracting pollinators. There have been few studies on the elaborate structure of petals in the tribe Isopyreae (Ranunculaceae). Seven genera in Isopyreae (Aquilegia, Semiaquilegia, Urophysa, Isopyrum, Paraquilegia, Dichocarpum, and Leptopyrum) have petals that vary in morphology, and two genera (Enemion and Thalictrum) have no petals. The petals of nine species belonged to 7 genera in the tribe were studied to reveal their nectary structure, epidermal micromorphology and ancestral traits. The petal nectaries of Isopyreae examined in this study were located at the tip of spurs (Aquilegia yabeana and A. rockii), or the bottom of shallow sacs (Semiaquilegia adoxoides, Urophysa henryi, Isopyrum manshuricum, and Paraquilegia microphylla), a cup-shaped structure (Dichocarpum fargesii) and a bilabiate structure (Leptopyrum fumarioides). The petal nectary of eight species in Isopyreae (except A. ecalcarata) was composed of secretory epidermis, nectary parenchyma, and vascular tissues, and some sieve tubes reached the secretory parenchyma cells. Among the eight species with nectaries examined in the present study, A. yabeana had the most developed nectaries, with 10-15 layers of secretory parenchyma cells. The epidermal cells of mature petals of the nine species were divided into 11 types. Among these 11 types, there were two types of secretory cells and two types of trichomes. Aquilegia yabeana and A. rockii had the highest number of cell types (eight types), and I. manshuricum and L. fumarioides had the lowest number of cell types (three types). Aquilegia ecalcarata had no secretory cells, and the papillose conical polygonal secretory cells of D. fargesii were different from those of the other seven species with nectaries. Trichomes were found only in Aquilegia, Semiaquilegia, Urophysa, and Paraquilegia. The ancestral mode of nectar presentation in Isopyreae was petals with hidden nectar (70.58%). The different modes of nectar presentation in petals may reflect adaptations to different pollinators in Isopyreae.

Extrafloral nectary development, characterization and secretion in Chamaecrista debilis and Chamaecrista desvauxii var. langsdorfii (Leguminosae, Caesalpinioideae)

Although the petiole glands in Chamaecrista are usually termed extrafloral nectaries (EFNs), additional studies on the morphoanatomy and chemical nature of the exudates are necessary to properly classify a plant secretory structure. The correct classification of such structures is also important in taxonomic and phylogenetic studies. Based on standard anatomical procedures for light microscopy our study aims to broaden our current understanding of the EFNs in Chamaecrista. We describe and compare the ontogenesis and the morphoanatomy of the petiole EFNs in C. debilis and C. desvauxii var. langsdorfii, species that belong to two distinct sections in Chamaecrista. The morphoanatomy along with the presence of sugars in exudates supports the classification of the petiole glands in both species as EFNs. The EFN development is rapid, and their secretory activity starts before the young leaves complete their expansion. The major difference among the EFNs of both species is their outer morphology which is useful on the taxonomy. Both EFNs are anatomically similar and composed of a secretory epidermis, a nectariferous parenchyma and vascular tissue more abundant in phloem in comparison to xylem.

Pericarp histogenesis and histochemistry during fruit development in Butia capitata (Arecaceae).

Palm fruits show great structural complexity, and in-depth studies of their development are still scarce. This work aimed to define the developmental stages of the fruit of the neotropical palm Butia capitata and to characterize the ontogenesis of its pericarp. Biometric, anatomical, and histochemical evaluations were performed on pistillate flowers and developing fruits. The whole fruit develops in three phases: (I) histogenesis (up to 42days after anthesis - DAA), when the topographic regions of the pericarp are defined; (II) pyrene maturation (42 to 70 DAA), when the sclerified zone of the pericarp is established; and (III) mesocarp maturation (70 to 84 DAA), when reserve deposition is completed. During pericarp ontogenesis (i) the outer epidermis and the outer mesophyll of the ovary give origin to the exocarp (secretory epidermis, collenchyma, parenchyma, sclerenchyma, and vascular bundles); (ii) the median ovarian mesophyll develops into the mesocarp, with two distinct topographical regions; (iii) the inner ovarian epidermis originates the endocarp; and in the micropylar region, it differentiates into the germination pore plate, a structure that protects the embryo and controls germination. (iv) Most of the inner region of the mesocarp fuses with the endocarp and, both lignified, give rise to the stony pyrene; (v) in the other regions of the mesocarp, carbohydrates and lipids are accumulated in a parenchyma permeated with fiber and vascular bundles. The development of the B. capitata pericarp presents high complexity and a pattern not yet reported for Arecaceae, which supports the adoption of the Butia-type pyrenarium fruit class.

Flower and Spikelet Construction in Rapateaceae (Poales).

The family Rapateaceae represents an early-divergent lineage of Poales with biotically pollinated showy flowers. We investigate developmental morphology and anatomy in all three subfamilies and five tribes of Rapateaceae to distinguish between contrasting hypotheses on spikelet morphology and to address questions on the presence of nectaries and gynoecium structure. We support an interpretation of the partial inflorescence (commonly termed spikelet), as a uniaxial system composed of a terminal flower and numerous empty phyllomes. A terminal flower in an inflorescence unit is an autapomorphic feature of Rapateaceae. The gynoecium consists of synascidiate, symplicate, and usually asymplicate zones, with gynoecium formation encompassing congenital and often also postgenital fusions between carpels. Species of Rapateaceae differ in the relative lengths of the gynoecial zones, the presence or absence of postgenital fusion between the carpels and placentation in the ascidiate or plicate carpel zones. In contrast with previous reports, septal nectaries are lacking in all species. The bird-pollinated tribe Schoenocephalieae is characterized by congenital syncarpy; it displays an unusual type of gynoecial (non-septal) nectary represented by a secretory epidermis at the gynoecium base.

Secretory Patterns in Colleters of Apocynaceae.

Colleters of Apocynaceae are glands related to different types of protection of vegetative and floral meristems through the production of mucilage or a mixture of many different compounds. Although several anatomical papers have shown histological and histochemical aspects of colleters of the family, almost nothing is known about their secretory process. In this study, we analyzed two types of colleters in Apocynaceae: one produces mucilage and lipophilic compounds, while the other produces an exclusively mucilaginous secretion. The secretory epidermis of the colleters of Allamanda schottii and Blepharodon bicuspidatum has a dense cytoplasm with organelles responsible for the production of mucilage and lipids. This heterogeneous secretion is released through granulocrine and eccrine mechanisms and is temporarily stored in a subcuticular space before crossing the cuticle. Conversely, colleters of Mandevilla splendens and Peplonia axillaris produce only mucilage and have a very different secretory apparatus. The mechanism of secretion is granulocrine, and the exudate is firstly accumulated in a large periplasmic space and later in an intramural space before crossing the cuticle. Notably, the structure of the cuticle varies according to the secretion composition. Although the colleters of the family are histologically similar, this study demonstrates a metabolic and subcellular variability previously unknown for Apocynaceae.

Morphoanatomy and ecology of the extrafloral nectaries in two species of Passiflora L. (Passifloraceae)

• The number of layers of the secretory epidermis varies according to the subgenera. • The secretor phase is evident with the distention of the cuticle. • The glucose occurrence in the exudates of the EFN in the leaves, several genera of ants and fungi associated to those structures allowed to identify those structures as extrafloral nectaries. The foliar glands of Passiflora are generally known as extrafloral nectaries, which, unlike floral nectaries, are not related to pollination. The present study describes and analyzes the foliar glands found in Passiflora ceratocarpa and Passiflora quadrangularis , in order to confirm their identity as extrafloral nectaries and discuss the taxonomic and ecological implications of these structures. The study material was collected in the metropolitan region of Belém (Brazil) and submitted to standard protocols for the analysis of plant anatomy by light and scanning microscopy, as well as histochemical testing. The extrafloral nectaries of the two species are anatomically very similar, including a multiseriate palisade epidermis, a nectariferous parenchyma consisting of voluminous, thin-walled cells, and predominantly phloematic vascularization. Their chemical composition is also highly similar, and includes sugars, and lipids. Five ant genera were found visiting the two Passiflora species, of which Camponotus was the most abundant, being found on both the study species.

Colleters, Extrafloral Nectaries, and Resin Glands Protect Buds and Young Leaves of Ouratea castaneifolia (DC.) Engl. (Ochnaceae).

Buds usually possess mechanical or chemical protection and may also have secretory structures. We discovered an intricate secretory system in Ouratea castaneifolia (Ochnaceae) related to the protection of buds and young leaves. We studied this system, focusing on the distribution, morphology, histochemistry, and ultrastructure of glands during sprouting. Samples of buds and leaves were processed following the usual procedures for light and electron microscopy. Overlapping bud scales protect dormant buds, and each young leaf is covered with a pair of stipules. Stipules and scales possess a resin gland, while the former also possess an extrafloral nectary. Despite their distinct secretions, these glands are similar and comprise secreting palisade epidermis. Young leaves also possess marginal colleters. All the studied glands shared some structural traits, including palisade secretory epidermis and the absence of stomata. Secretory activity is carried out by epidermal cells. Functionally, the activity of these glands is synchronous with the young and vulnerable stage of vegetative organs. This is the first report of colleters and resin glands for O. castaneifolia. We found evidence that these glands are correlated with protection against herbivores and/or abiotic agents during a developmental stage that precedes the establishment of mechanical defenses.

Resolving the non-papilionaceous flower of Camoensia scandens, a papilionoid legume of the core genistoid clade: development, glands and insights into the pollination and systematics of the group.

Camoensia scandens is a papilionoid legume inserted in the core genistoid clade. It has large, crepuscular, scented flowers but the corolla is non-papilionaceous, which deviates from the pattern found in the subfamily. The vexillum has a folded claw, forming a tube, which is opposed to the androecium opening; all petals have yellow-gold crinkled margins. In addition, there is a long hypanthium, which stores a translucid liquid. The goal of this study is to elucidate the ontogenetic pathways that result in such a peculiar flower and the glands responsible for the sweet fragrance of the petals. Floral buds and flowers were processed for SEM, TEM and light microscopy analyses. Five sepals arise unidirectionally followed by five petals that initiate simultaneously. After the petals, 11 stamens emerge unidirectionally; a pair of adaxial stamens is opposite to the vexillum. In the intermediate developmental stages the sepals unite basally; the two adaxial sepals unite with each other to a greater extent than with the other sepals. The filaments are basally connate, forming a tube with an adaxial opening at the base. The carpel emerges concomitantly with the two abaxial antepetalous stamens. The long hypanthium forms from the outer floral organs (base of the sepals, petals, filaments) and is attached tothe base of the stipe. The corolla is noticeable in the intermediate stages of development. The crinkled golden margins house scent glands formed of a secretory epidermis with secretory trichomes and secretory subepidermal cells. The odor is composed of neutral polysaccharides, nitrogenous substances and essential oils. An extensive nectariferous region is found on the inner surface of the hypanthial tube. The nectar is translucent, viscous and released through large pores. The comparison of our data with that of other genistoid flowers enabled discussions about the pollination and systematics of the group.

Diversity of petals in Berberidaceae: development, micromorphology, and structure of floral nectaries.

Petals are important floral organs that exhibit considerable morphological diversity in terms of colour, shape, and size. The varied morphologies of mature petals can be linked to developmental differences. The petals of Berberidaceae (a core group of Ranunculales) range from flat sheets to complex structures with nectaries, but studies on petal development and structural diversity in this group are lacking. Here, the petal development, structure, and micromorphology of seven Berberidaceae genera are characterized by microscopy to clarify the diversity of petals within this group. The results indicate that no common petal-stamen primordium exists, that petal development proceeds through five stages, and that the differentiation responsible for the diversity of the mature petals occurs during stage 4. Processes contributing to the morphological diversity of mature petals include edge thickening, gland formation, and spur formation. Nandina and Diphylleia lack nectaries. Gymnospermium has saccate nectaries, Caulophyllum has nectaries on the petal margin, Epimedium has spur nectaries, and Berberis and Mahonia have glands at the base of petals. Petal nectaries usually consist of a secretory epidermis, two to twenty layers of secretory parenchyma cells, and vascular tissues. Eleven distinct cell types were observed in the petal epidermis, three of which are secretory; papillose cells appear to be absent in Diphylleia, which shows relatively little micromorphological variation. The ancestors of Berberidaceae may have nectaries in thickened areas of their petals. The micromorphology and nectary structures of the petals in Ranunculales are also compared.

Nectary and elaiophore work together in flowers of Xylopia aromatica (Annonaceae): structure indicates a role in pollination

Secretory structures that produce floral rewards have rarely been reported for Annonaceae. We identified a glandular region in Xylopia aromatica (Lam.) Mart., which consisted of a nectary and an elaiophore. This study aimed to describe the structure and secretory process of these glandular structures, which are highly correlated with 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 highly similar structure. Nectar attracts pollinators to the pollination chamber, whereas lipids seem to act in pollen adhesion to the body of pollinators. Both of exudates appear to act in complementary ways during pollination.

Extranuptial nectaries in flowers: ants increase the reproductive success of the ant-plant Miconia tococa (Melastomataceae).

Although the production of extranuptial nectar is a common strategy of indirect defence against herbivores among tropical plants, the presence of extranuptial nectaries in reproductive structures is rare, especially in ant-plants. This is because the presence of ants in reproductive organs can generate conflicts between the partners, as ants can inhibit the activity of pollinators or even castrate their host plants. Here we evaluate the hypothesis that the ant-plant Miconia tococa produces nectar in its petals which attracts ants and affects fruit set. Floral buds were analysed using anatomical and histochemical techniques. The frequency and behaviour of floral visitors were recorded in field observations. Finally, an ant exclusion experiment was conducted to evaluate the effect of ant presence on fruit production. The petals of M. tococa have a secretory epidermis that produces sugary compounds. Nectar production occurred during the floral bud stage and attracted 17 species of non-obligate ants (i.e. have a facultative association with ant-plants). Ants foraged only on floral buds, and thus did not affect the activity of pollinators in the neighbouring open flowers. The presence of ants in the inflorescences increased fruit production by 15%. To our knowledge, the production of extranuptial nectar in the reproductive structures of a myrmecophyte is very rare, with few records in the literature. Although studies show conflicts between the partners in the ant-plant interaction, ants that forage on M. tococa floral buds protect the plant against floral herbivores without affecting bee pollination.

A structural review of foliar glands in Passiflora L. (Passifloraceae).

Extrafloral glands in Passifloraceae species have aroused the interest of many researchers because of their wide morphological diversity. The present work analyzed the foliar glands on 34 species of Passiflora from samples containing glands in the petiole and foliar blade fixed in 50% solution of formaldehyde-ethanol-acetic acid and stored in a 70% ethanol solution. For anatomical analyses, part of the material was embedded in Paraplast, longitudinally sectioned and double stained with safranin and astra blue. Scanning electron microscopy analysis was also carried out. To analyze the presence of sugars in the secretion of foliar glands, a glucose strip test was used. Based on the results of morphological, anatomical and glucose strip tests, the foliar secretory glands in Passiflora can be grouped into two categories: Type I glands, defined as nectaries, can be elevated or flattened, and can have a sugar content high enough to be detected by the glucose strip test analysis. Type II glands are elevated and did not show a positive reaction to the glucose strip test. From an anatomical viewpoint, glands characterized as extrafloral nectaries show a multistratified secretory epidermis, typically followed by two flat layers of nectariferous parenchyma with dense content. Internal to these layers, vascular bundles are immersed in the subsecretory parenchyma and terminate in phloem cells. On the other hand, type II glands show a single layer of elongated secretory epidermal cells. Internal to this single layer, parenchyma and vascular tissue with both phloem and xylem elements can be observed. The analyzed species show a wide diversity of gland shape and distribution, and the combined analysis of morphology, anatomy and preliminary tests for the presence of glucose in the exudate in different Passiflora subgenera suggests the occurrence of two categories of glands: nectaries and resin glands.

Leaf glands of Banisteriopsis muricata (Malpighiaceae): distribution, secretion composition, anatomy and relationship to visitors

ABSTRACT Leaf glands are common structures in Malpighiaceae and exhibit great morphological diversity, yet information on their anatomy, secretion and type of visitors remains scarce. The aim of this study was to describe the distribution, anatomical development and chemical and functional properties of leaf glands of Banisteriopsis muricata (Malpighiaceae). Leaves at different stages of development were collected and processed according to standard techniques for light and scanning electron microscopy. Secretion composition was determined by histochemical tests and test-strips, while gland funciton was determined by field observation of interactions with visitors. Leaf glands were located on the petiole and on the abaxial base of the leaf blade. The gland secretion was found to be a protein-rich nectar that was foraged upon by ants ( Solenopsis); it was found accumulated in subcuticular spaces without pores or stomata for its release. Leaf glands were found to develop from protoderm and ground meristem, and consisted of typical secretory epidermis, nectariferous parenchyma and vascularized subnectariferous parenchyma. Therefore, it can be concluded that the distribution, chemical nature of secretion and anatomy of leaf glands of B. muricata characterize them as EFNs, while foraging by ants indicate a mutualistic relationship that possibly protects the plant against herbivores.

Різноманітність септальних нектарників Однодольних

Досліджено питання різноманітності септальних нектарників в Однодольних та ступінь їх вивченості для з’ясування можливості використання цих ознак у систематиці. Септальні нектарники наявні лише в Однодольних і, ймовірно, являють собою ключову інновацію цієї групи.