Three new species of Salacioideae (Celastraceae)

This paper describes three new species of Salacioideae Cheiloclinium and Salacia (Celastraceae) from South America: C. brevipetiolatum Lombardi is characterized by its very short, only 5 mm long petioles; S. krigsneri Lombardi is distinguished by its dichasium (inflorescence) with shortened lateral branches, a unique feature among neotropical species; and S. vernicosa Lombardi can be discerned from other species by its fascicled inflorescences and large leaves, dried inflorescence covered with resinous substance, tubuliform flowers, flat, ring‐shaped disc, and berries with ribs at base and lobes at apex.     

Androecium and floral nectaries ofHarungana madagascariensis (Clusiaceae)

The mature flower ofHarungana madagascariensis (Choisy)Poir. has an androecium of five antipetalous fascicles, consisting of four stamens each. The stamen fascicles alternate with five indented nectary scales. A SEM-study of the floral development, as well as a study of the floral anatomy was carried out to understand whether the nectariferous scales represent staminodia or are receptacular in nature and consequently whether or not the androecium ofHarungana, and theClusiaceae in general, is originally diplostemonous. The five petals originate by the splitting of petal-stamen complexes. Next the upper part of each complex differentiates basipetally in four stamens. The stamens remain fascicled and are lifted on a long stalk at maturity. Five carpel primordia are initiated united in a low ringwall. The five nectary scales appear after carpel inception and develop an external morphology reminiscent of anthers. The floral anatomy reveals an independent origin of sepal median traces and common sepal lateral traces, free petal traces, stamen fascicle traces and alternating vascular tissue which supplies the nectaries. The petal-stamen complexes are the result of a retardation in petal inception, linked with the absorption of petal tissue into the stamen primordia. The development of the stamen fascicles is discussed; it is suggested that they are of a secondary nature and do not appear as a reduction from a multistaminate androecium. The external morphology and vascular anatomy of the scales speaks in favour of a staminodial nature. The comparison with some other species of theClusiaceae gives evidence of a diplostemonous ancestry of the androecium.     

Micromorphology and ultrastructure of the floral nectaries of Polemonium caeruleum L. (Polemoniaceae)

The Polemoniaceae family forms flowers diverse in the terms of pollination methods and nectar types. The micromorphology of the nectary surface and the tissue structures as well as the ultrastructure of the cells of the floral nectaries in Polemonium caeruleum L. were examined using light, scanning and transmission electron microscopy. A bowl-shaped nectary, detached from the ovary, grows at its base. Its contour shows folds with depressions in the places where the stamens grow, forming five-lobed disc (synapomorphic character). Nectar is secreted through modified anomocytic stomata, which are formed in the epidermis covering the tip and the lateral wall of the projection located between the staminal filaments. The undulate nectary consists of a single-layered epidermis and three to nine layers of parenchymal cells. The cells of the nectary contain a dense cytoplasm, numerous plastids with an osmophilic stroma and starch grains, well-developed endoplasmic reticulum, as well as a large number of mitochondria interacting with the Golgi bodies. The ultrastructure of nectary cells indicates the granulocrine secretion mechanism and diversified transport of nectar.     

Leaf colleters in Tontelea micrantha (Celastraceae,Salacioideae): Ecological,morphological and structural aspects

The colleter secretion can be useful to protect plants of Cerrado (Brazilian savanna) biome during the long and pronounced dry season. This study describes the presence of colleters in Tontelea micrantha and represents the first record of these structures in Celastraceae. To investigate colleter structure and their secretory processes, young leaves were collected, fixed, and processed according to conventional techniques for light, and electron microscopy. Colleters were observed at the marginal teeth on the leaf. They produce mucilaginous secretions that spread over the leaf surface. After secretory phase, colleters abscise. The secretory epithelium is uniseriate and composed of elongated cells whose dense cytoplasm is rich in organelles. The ultrastructure of the secretory cells is compatible with the pectin-rich secretion. Observations of the young leaves surface revealed the presence of superficial hydrophilic secretion films that appeared to have the function of maintaining the water status of those organs.     

Characteristics of floral nectaries and nectar in two species of Crataegus (Rosaceae)

 The structure of floral nectaries of Crataegus coccinea and C. crus-galli was examined using light and scanning electron microscopy. The radial length of the floral nectary, measured from longitudinal sections of flowers, was 30% larger in C. crus-galli than in C. coccinea. For both Crataegus species the glandular tissue thickness was similar – approx. 400 μm. Also, the number of stomata per mm² of nectary surface in C. crus-galli was much higher (by 43%) than for C. coccinea. Stomata were situated in deep hollows. For both taxa the period of nectar secretion was 4 days. The mean quantity of total sugar in nectar per 10 flowers of C. crus-galli and C. coccinea was 3.87 mg and 0.33 mg, respectively. Received August 28, 2002; accepted December 17, 2002 Published online: June 2, 2003     

Morphology, development and homologies of the perianth and floral nectaries in Croton and Astraea (Euphorbiaceae-Malpighiales)

New observations are presented on the ontogeny, vasculature and morphology of both staminate and pistillate flowers of Croton and Astraea. These data support earlier hypotheses that the filamentous structures in pistillate flowers represent reduced and transformed petals. Staminate flowers of both genera possess five free nectaries, which are vascularised by divergences of the sepal traces in Croton and unvascularised in Astraea. In pistillate flowers, there are five separate non-vascularised nectaries in Astraea, but in Croton there is a single nectariferous disk that is vascularised by divergences of the sepal traces. The nectaries are initiated late in floral development, but their location indicates that they could represent the outer stamen whorl transformed into secretory staminodes. Other glandular structures occur in pistillate flowers of most Croton species, resulting in flowers with two secretory organ whorls. In these cases, the inner whorl is formed by modified staminodes. Our observations support the recent segregation of Astraea species from the larger genus Croton. Despite strong similarities between the two genera, there are clear structural differences, including the presence of colleters in Astraea (absent in Croton), moniliform trichomes on petals (rather than simple trichomes in Croton), non-vascularised nectaries (vascularised in Croton) and reduced, non-secretory filamentous structures (well developed and secretory in Croton).     

Additional notes on the floral biology of neotropical Lecythidaceae

Observations on the floral biology of seven species of New World Lecythidaceae, including the first report of bat pollination for neotropical members of the family, are presented. The shift from actinomorphic flowers with many stamens to zygomorphic flowers with fewer stamens and the concomitant change from pollen to nectar as the pollinator reward are discussed and related to the respective pollinators. Several mechanisms which operate to reduce competition for pollinators between sympatric species of the family are suggested.     

Anatomy and ultrastructure of the floral nectary in Peganum harmala L. (Nitrariaceae)

Anatomy and ultrastructure of the floral nectary of Peganum harmala L. were studied using light and transmission electron microscopy. The floral nectary was visible as a glabrous, regularly five‐lobed circular disc encircling the base of the ovary. Anatomically, it comprised a single layered epidermis and 15–20 layers of small, subepidermal secretory cells overlying several layers of large, ground parenchyma cells. The floral nectary was supplied by phloem and both sieve tubes and companion cells were found adjacent to the ground parenchyma. Based on our ultrastructural observations, plastids of secretory cells during the early stages of development were rich in starch grains and/or osmiophilic plastoglobuli, but these disappeared as nectar secretion progressed. The nectar appeared to exude through the modified stomata along symplastic and apoplastic routes. The abundant plastids and mitochondria suggest an eccrine mechanism of nectar secretion in P. harmala.     

Terpenoids from Tripterygium doianum (Celastraceae)

The extract of Tripterygium doianum (Celastraceae) afforded three triterpenoids [3beta-acetoxy-11-ursen-13alpha,30-olide, 25-chloro-24-hydroxytirucall-7-en-3-one and tirucall-7-en-3,24-dione], two sesquiterpenoids [5alpha-acetoxy-1beta,8alpha-bis-cinnamoyl-4alpha-hydroxydihydroagarofuran and 5alpha-acetoxy-1beta-benzoyl-8alpha-cinnamoyl-4alpha-hydroxydihydroagarofuran] and nine known triterpenoids. Their structures were established based on spectroscopic studies.     

Distribution and morphology of extrafloral nectaries in some Cucurbitaceae

A study of extrafloral nectaries has been made in the Cucurbitaceae to ascertain their structure and assess their taxonomic potential. Nineteen species representing nine Old World genera and one New World genus were examined. These included Telfairia occidentalis, Telfairia pedata, Momordica charantia, Lagenaria siceraria, Citrullus lanatus, Luffa aegyptiaca, Cucurbita moschata and Trichosanthes cucumerina , which are of economic importance and cultivated in Nigeria for their leaves and/or fruits.
Observation of the regularity of ant and insect-visitors, along with tests for glucose and β-glucosidase enzymes, revealed the presence of extrafloral nectaries in nine species. Considerable variation exists in the distribution and morphology of nectaries between genera, especially in the tribe Benincaseae. The nutritional and ecological significance of the occurrence of extrafloral nectaries in Telfairia occidentalis is discussed.     

A macro- and micromorphological survey of floral and extrafloral nectaries in the epiphytic cactus Rhipsalis teres (Cactoideae: Rhipsalideae)

Floral and extrafloral nectaries in plants favor pollination and defense against herbivory. Despite their wide distribution in plants and differences in position, structure, and topography, their biological and systematic significance has been underutilized. This study investigated the macro- and micromorphology of floral and extrafloral nectaries in the epiphytic cactus Rhipsalis teres and reports unusual bristle-like structures (bracteoles) functioning as extrafloral nectaries in the cactus family. The floral nectary is disc-shaped embedded in the hypanthial floral cup with anomocytic stomata as secreting structures present on the epidermal nectarial tissue. Small multicellular bristle-like extrafloral nectar-secreting structures, homologues to bracts, were observed on the plants’ stems and function as bracteolar nectaries having a relatively long and continuous secretory activity throughout several stages of the reproductive structures. Both the floral and bracteolar nectaries are functional. It is possible that in the latter nectar discharge occurs though epidermal cells, which build up pressure inside as nectar accumulates, thereby ending with rupture of the cuticle to release the liquid. The nectar in both secreting structures is scentless and colorless, and the concentration from floral nectaries is slightly lower than that of the bracteolar nectaries, 70.6% and 76.4%, respectively. The relatively higher concentration in the latter might be correlated with exposure, relative humidity and water evaporation, leading to crystallization of sugars on the stem surface in a short period of time.     

Anatomy and ultrastructure of mycorrhizal associations of neotropical Ericaceae

Ericaceae are obligatory associated with symbiotic fungi forming several, distinctive categories of mycorrhizas. While ericoid, arbutoid, and monotropoid mycorrhizas are known since many years from ericads of the northern hemisphere and the ericoid mycorrhiza also from Australia, a further mycorrhizal category with hyphal sheath, Hartig net, and intracellular colonization was described by us recently and termed cavendishioid mycorrhiza because it was found on Cavendishia nobilis, a species belonging to the Andean clade (Vaccinioideae) of Ericaceae. As the previous findings indicated a correlation between the mycorrhizal category and the systematic position of Ericaceae, we tested the hypothesis that other ericads of the Andean clade might also form cavendishioid mycorrhizas, while ericads occurring in the same area but not belonging to the Andean clade might not. Mycorrhizas of 20 different ericaceous species, 15 belonging to the Andean clade and 5 to other Vaccinioideae or Ericoideae, were sampled in the tropical mountain rain forest area of South Ecuador and investigated by light and electron microscopy. All the 15 members of the Andean clade ericads displayed a hyphal sheath, as well as inter- and intracellular colonization by hyphae as was found on Cavendishia previously. The five species not belonging to the Andean clade ericads displayed only intracellular colonization by hyphae and hence were typical ericoid mycorrhizal. Ultrastructural studies revealed Sebacinales and ascomycetes as mycorrhiza formers in both associations even within one single cell. The results thus support the hypothesis that the Andean clade of Ericaceae forms mycorrhizas distinct from the arbutoid category and most likely presents an independent evolutionary line in the Ericaceae derived from the ericoid mycorrhizas, justifying the new term “cavendishioid mycorrhiza”.     

The floral nectaries of Hibiscus rosa-sinensis in. A morphometric and ultrastructural approach

The secretory hairs of Hibiscus rosa-sinensis nectaries have been studied ultrastructurally, particularly at stages before, during and after secretion. Morphometric cytology revealed considerable changes in the volume of endoplasmic reticulum (ER) and the vacuoles. At least three different forms of ER have been noticed, cisternal, tubular and vesicular. The intermediate cells of the hairs are ultrastructurally and morphometrically similar to the tip cell, suggesting their probable involvement both in a symplastic prenectar transport via the plasmodesmata and in nectar release into an extracellular space provided by the lateral cell walls. Nectar would then be apoplastically moving towards the tip cell, where it is forcibly expelled to the outside via transient pores of the cuticle.
Ultrastructural evidence indicates that ER is the cell compartment principally involved both in prenectar transport and nectar elimination. In the hair cells it provides a "secretory reticulum" mediating between prenectar accumulation and nectar release. Vacuoles are voluminous in the basal cells, and in all cell types of old nectaries. The results are discussed in relation with other plant glands, especially with the closely related Abutilon nectaries.     

Hydnocarpus sharmae (Flacourtiaceae) is Siphonodon celastrineus (Celastraceae)

Notes on Siphonodon celastrineus (Celastraceae). Hydnocarpus sharmae , a new species described recently from Andaman Islands, India, is Siphonodon celastrineus of Celastraceae and not a species of Flacourtiaceae.     

Anatomy of the extrafloral nectaries in species of Chamaecrista section Absus subsection Baseophyllum (Leguminosae,Caesalpinioideae)

In this paper the ontogenesis and histochemistry of the petiolar glands found on the petiole/rachis of the eight Chamaecrista species of the section Absus, subsection Baseophyllum (Leguminosae, Caesalpinioideae) are studied by using light microscopy techniques, aiming to characterise these structures and to provide taxonomic characters which may be useful in phylogenetic approaches. Strips for glucose identification reacted positively with the exudates of the glands, confirming the presence of nectar in the secretion, characterising these glands as extrafloral nectaries (EFN). Histochemical tests also detected the presence of neutral and acid muco-polysaccharides, pectins, mucilages, total proteins, and phenolic compounds in the EFNs. The EFNs arise from a group of meristem cells (protodermis, ground meristem and procambium) in the petiole/rachis. All EFNs of the investigated taxa share some morpho-anatomical characters, so that their peculiarities are too weak to be used alone in the identification of particular species. Rather their similarities may be used to include these species into a single group, supporting the hypothesis of monophyly of the subsection Baseophyllum.     

Comparative studies on structure of the floral nectaries and the abundance of nectar production of Prunus laurocerasus L.

Protoplasma - There is very scanty information concerning the floral nectary structure and nectar secretion in Prunus laurocerasus L. Therefore, the aim of the study was to determine the...