Catasetum Species Research Articles

<i>Catasetum tavaresii</i> (Catasetinae), a new species from Central Brazilian Amazon

A new Catasetum species from Brazilian Amazon, more specifically from the “Floresta Nacional de Saracá-Taquera” (State of Pará), is proposed, described and illustrated. This new taxon belongs to the subgenus Catasetum, section Isoceras, subsection Isoceras, whose representatives have symmetrical and parallel antennae. It is compared with C. nhamundaense, C. garnettianum and C. barbatum, all with the same antennae characteristics and belonging to the "C. cristatum alliance". Among related species, C. tavaresii differs mainly in the lip structure. We also give data on geographical distribution, habitat, phenology, flower visitors, and preliminary conservation status.

Volatile Constituents from Catasetum (Orchidaceae) Species with Occurrence in the Brazilian Amazon.

Catasetum Rich. ex Kunth is a genus of Neotropical orchids distributed in Central and South American regions. In the Brazilian Amazon, there are more than 60 species of Catasetum. The floral aromas of orchids are little known, particularly of Catasetum species. This work aimed to analyze the chemical constituents of the volatile concentrates of eight Catasetum specimens from the Amazon: C. alatum (1), C. albovirens (2), C. barbatum (1), C. ciliatum (2), C. galeritum (1), and C. gnomus (1). Gas chromatography (GC) and gas chromatography-mass spectrometry (GC-MS) analyzed and identified the constituents of the volatile concentrates, and principal component analysis (PCA) and hierarchical cluster analysis (HCA) were used in the multivariate statistical analysis. The Catasetum main constituents in descending order and above 10% were trans-geranylgeraniol, 1,4-dimethoxybenzene, linalool, 2-phenylethyl acetate, geraniol, 7-epi-1,2-dehydro-sesquicineole, 1,8-cineole, benzyl acetate, limonene, methyl salicylate, (E)-β-farnesene, anisyl butyrate, cis-carvone oxide, cadin-4-en-10-ol, indole, α-pinene, and δ-cadinene. Multivariate statistical analysis of Catasetum species showed that C. barbatum, C. albovirens, and C. gnomus are distinct from the other studied species, while C. alatum, C. ciliatum, and C. galeritum presented the same primary classes of compounds. These results contribute to a better understanding of the genus Catasetum chemotaxonomy.

The influence of pre-treatment on germination of three species of Catasetum (Orchidaceae)

Abstract: Asymbiotic germination techniques are successful in species of the Catasetum genus. The diverse composition of the culture media can be critical; however, viable seeds are required for asymbiotic germination. The reliable method for viability assessment is the tetrazolium test. A decisive step in the efficiency of the tetrazolium test is the seeds preconditioning with sucrose solution, which has the potential to improve germination. Therefore, this work aimed to evaluate the seed germination of three species of the genus Catasetum in culture media, preconditioned or not with sucrose solution. Seeds of the species Catasetum osculatum, Ctsm. galeritum and Ctsm. complanatum were assessed by tetrazolium test and germinated in two different media, pretreated or not with 10% sucrose solution. The statistical analysis showed that the use of sucrose pretreatment significantly increased the germination rates of the species. We conclude that the pretreatment with 10% sucrose for 24 hours, regardless of the species and the culture medium, significantly increases the germination of Ctsm. complanatum, Ctsm. galeritum and Ctsm. osculatum seeds.

Floral Scent Chemistry and Pollinators of a Sexually Dimorphic Neotropical Orchid

Catasetum is a speciose Neotropical orchid genus of which male and female flowers emit scents acting both as attractant and reward for their exclusive pollinators, male orchid bees (Euglossini: Apidae). In Catasetum, it is well known that flowers display a remarkably morphological sexual dimorphism. However, it remains poorly investigated whether this is also true for floral scents. Here, we investigated the pollination ecology and floral scent traits (chemistry and total emission) of C. maranhense, a species endemic to the Brazilian N/NE region. Males of Euglossa securigera are the only pollinators of C. maranhense. The floral scent of C. maranhense is composed of 29 volatile compounds, with eucalyptol, indole, (E)-Methyl p-methoxycinnamate, and (Z)-Methyl p-methoxycinnamate accounting for more than 80% of the scent bouquet. No sexual dimorphism was detected in any of the traits investigated. We discuss the ecological and evolutionary significance of our findings to Catasetum species and other unisexual perfume plants.

Sexual dimorphism in floral scents of the neotropical orchid Catasetum arietinum and its possible ecological and evolutionary significance

Abstract Dioecy in angiosperms is often associated with sexual dimorphism in floral traits other than the sexual organs. Species of the neotropical orchid genus Catasetum produce unisexual flowers characterized by a remarkable morphological sexual dimorphism. Catasetum species emit strong floral perfumes that act as both signal and reward for male euglossine bee pollinators. Although the role of floral perfumes of Catasetum in attracting euglossine pollinators is well investigated, little is known about whether perfumes differ between floral sexes and, if they do, whether this chemical dimorphism influences the pollination ecology of the plants. Taking Catasetum arietinum as a model species, our aim was to observe the behaviour of pollinators on male and female flowers and to compare scent properties (i.e. chemical composition, total amount and temporal fluctuation) of male and female flowers. Floral scent samples were collected by using dynamic headspace methods and were analysed via gas chromatography coupled with mass spectroscopy (GC-MS). Catasetum arietinum is pollinated by males of two Euglossa species (i.e. E. nanomelanotricha and E. securigera). Bees approached male and female inflorescences of C. arietinum in similar proportions but landed significantly more often and spent more time on female flowers, which emitted more scent than male flowers. Furthermore, the amount of scent emitted varied across the different times of sampling, corresponding to the pattern of the diel foraging activity of pollinating bees on male and female flowers. The chemical composition of scents differed significantly between sexes. The two major compounds (Z)-methyl-p-methoxycinnamate and (E)-geranyl geraniol contributed most to this difference. This is the first case of sexual dimorphism reported in orchid floral perfumes. We discuss the influence of sex-specific floral scents on the behaviour of euglossine pollinators and offer new insights into the ecological and evolutionary significance of divergence in floral scents among dioecious plants.

Subtle Chemical Variations with Strong Ecological Significance: Stereoselective Responses of Male Orchid Bees to Stereoisomers of Carvone Epoxide.

Different enantiomers of chiral compounds within floral perfumes usually trigger distinct responses in insects; however, this has frequently been neglected in studies investigating semiochemicals in plant-pollinator interactions. Approximately 1000 neotropical plants produce floral perfumes as the only reward for pollinators, i.e. male euglossine bees. The chiral compound carvone epoxide is a key component of the scent bouquet of many perfume-rewarding plants that are pollinated by males of Eulaema. Here, we tested the biological activity of the four carvone epoxide stereoisomers to four Eulaema species occurring in the Atlantic Rainforest of NE-Brazil. We determined the stereochemistry of carvone epoxide in the floral scent of several Catasetum species, tested whether the antennae of bees respond differentially to these stereoisomers and investigated if there is a behavioural preference for any of the stereoisomers. We found that 1) Catasetum species emit only the (-)-trans-stereoisomer of carvone epoxide, 2) for E. atleticana and E. niveofasciata antennal responses to the (-)-trans-carvone epoxide were significantly stronger than those to (-)-cis-carvone epoxide, 3) the strength and pattern of antennal responses to all 4 stereoisomers (separately tested) did not differ among Eulaema species, and 4) there were significant differences in attractiveness of the four stereoisomers to the bees species with the (-)-trans-stereoisomer being particularly attractive. We assume (-)-trans-carvone epoxide to be the dominant isomer in perfume-rewarding plants pollinated by Eulaema. The universal occurrence of carvone epoxide in Catasetum species pollinated by Eulaema, suggests that this compound has evolved in perfume-rewarding as a specific attractant for Eulaema bees as pollinators.

Notes on pollination ecology and floral scent chemistry of the rare neotropical orchid Catasetum galeritumRchb.f.

AbstractThe neotropical orchid genus Catasetum embraces about 180 species that produce perfume as reward for pollinators (i.e. male euglossine bees). Among the ca. 1000 perfume‐rewarding plants, Catasetum species are the best studied with respect to their natural history. Nevertheless, the pollination ecology of most species (> 80%) remains unknown. Here, we investigated the pollination ecology and floral scent chemistry of C. galeritum, a rare species endemic to the poorly investigated Brazilian Amazon. Flowers of C. galeritum were visited only by male bees of Eufriesea superba. Its perfume bouquet was composed of six volatiles, with 1,4‐dimethoxybenzene accounting for about 85% of the total scent discharge. Curiously, this compound is a potent attractant of more than 40 euglossine species. The absence of euglossine species other than Ef. superba on flowers of C. galeritum might be, therefore, be mediated by a modifier effect of another compound(s) in its floral scent bouquet.

A new species of Catasetum (Cymbidieae, Epidendroideae, Orchidaceae) from the Southern region of the Brazilian Amazon

A new species of Catasetum has been found along the banks of the River Teles Pires, in the Southern region of the Brazilian Amazon. In the present study it is described and illustrated, and has its conservation status discussed. The species presents unique features and stands out among others found in the same region, and can be compared partially to C. mattosianum.

Pollination biology in the dioecious orchid Catasetum uncatum: How does floral scent influence the behaviour of pollinators?

Catasetum is a neotropical orchid genus that comprises about 160 dioecious species with a remarkable sexual dimorphism in floral morphology. Flowers of Catasetum produce perfumes as rewards, which are collected only by male euglossine bees. Currently, floral scents are known to be involved in the selective attraction of specific euglossine species. However, sexual dimorphism in floral scent and its eventual role in the pollination of Catasetum species have never been investigated. Here, we have investigated the pollination of Catasetum uncatum and asked: (1) Is floral scent a sexual dimorphic trait? (2) Does pollinarium removal/deposition affect scent emission? (3) Does sexual dimorphism in floral scent and changed scent emission have implications with regard to the behaviour of the pollinators? The frequency and behaviour of floral visitors were observed in non-manipulated flowers (both flower sexes) and in manipulated flowers (pistillate only) in which pollinaria were deposited. Scents of staminate and pistillate flowers (both manipulated and non-manipulated) were collected by using dynamic headspace methods and analysed chemically. Electrophysiological analyses were performed to detect compounds triggering antennal depolarisation in the euglossine species. C. uncatum is pollinated mainly by males of Euglossa nanomelanotricha. Pollinators were more frequent in pistillate than in staminate inflorescences. Bees approaching staminate flowers frequently flew away without visiting them, a behavioural pattern not observed in pistillate flowers. In the chemical analyses, we recorded 99 compounds, 31 of which triggered antennal depolarisation in pollinators. Multivariate analyses with the electrophysiological-active compounds did not detect differences between the scent composition of staminate and pistillate flowers. Pollinarium removal or deposition resulted in diminished scent emission within 24h in staminate and pistillate flowers, respectively. Surprisingly, bees discriminated pollinated from non-pollinated pistillate flowers as early as 2h after pollination. The rapid loss in the attractiveness of flowers following pollinarium removal/deposition can be interpreted as a strategy to direct pollinators to non-pollinated flowers. We have found no evidence that euglossine males discriminate staminate from pistillate flowers by means of floral scent. Instead, we speculate that bees use visual cues, such as sex dimorphic traits, to discriminate flowers of different sexes. Together, our results provide interesting insights into the evolution of floral signals in gender-dimorphic species and into its significance in plant reproductive biology.

Use of anatomical root markers for species identification in Catasetum (Orchidaceae) at the Portal da Amazônia region, MT, Brazil

Orchidaceae is one of the largest botanical families, with approximately 780 genera. Among the genera of this family, Catasetum currently comprises 166 species. The aim of this study was to characterize the root anatomy of eight Catasetum species, verifying adaptations related to epiphytic habit and looking for features that could contribute to the vegetative identification of such species. The species studied were collected at the Portal da Amazônia region, Mato Grosso state, Brazil. The roots were fixed in FAA 50, cut freehand, and stained with astra blue/fuchsin. Illustrations were obtained with a digital camera mounted on a photomicroscope. The roots of examined species shared most of the anatomical characteristics observed in other species of the Catasetum genus, and many of them have adaptations to the epiphytic habit, such as presence of secondary thickening in the velamen cell walls, exodermis, cortex, and medulla. Some specific features were recognized as having taxonomic application, such as composition of the thickening of velamen cell walls, ornamentation of absorbent root-hair walls, presence of tilosomes, composition and thickening of the cortical cell walls, presence of mycorrhizae, endodermal cell wall thickening, the number of protoxylem poles, and composition and thickening of the central area of the vascular cylinder. These traits are important anatomical markers to separate the species within the genus and to generate a dichotomous identification key for Catasetum. Thus, providing a useful tool for taxonomists of this group

Novelties in Catasetum (Orchidaceae) in the State of Rondônia, Brazil

AbstractThe State of Rondônia is rich in species of Catasetum that are still undervalued, which presents a major challenge in the preparation of a map that shows the distribution and all occurrences of the species of the genus. As a result of our studies, four new records are presented for the State of Rondônia and a new natural hybrid is described and illustrated. Samples of all species were collected for DNA extraction (aliquots kept in the Total DNA Bank of Plants UFPR – UPCB‐DNA) and vouchers deposited at the herbaria UFMT and the RB. (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

La pesadilla de lindley - la biología sexual de <i>catasetum</i> y <i>cycnoches</i>

The sexual dimorphism of the genera Catasetum and Cycnoches is now common knowledge to orchid growers and investigators. Female flowers of Catasetum are all non-resupinate with a hooded lip, whereas the male flowers can be non-resupinate with a hooded lip or resupinate with a differently shaped lip, depending on the species. Only with male flowers present can the species of a Catasetum can be determined. In Cycnoches, flowers of both sexes are resupinate with a slender and long, curved column, resembling a swan’s neck. The lip of male flowers of C. sect. Heteranthae is provided with finger-like projections, but female flowers of that section and those of C. sect. Cycnoches have an entire lip. Female flowers of both genera observed in the Botanical Garden of Munich bear pollinaria, but they are without any function. Slight movements of the female inflorescences of Catasetum cause the pollinaria to fall off, and as a result their presence is often overlooked. In female pollinaria of Catasetum the caudicles are absent, making pollination impossible in nature. Their pollen is germinable, and application of the pollinia to the stigma of the same flower yields viable seeds. The seldomobserved intermediate forms have a stigmatic cavity as in the male flowers. Their pollinaria are similar to those of the female flowers, so they are also non-functional. They do not serve either as males or females. In female Cycnoches, the anther cap does not fall off, so preventing pollination by such a pollinarium. The pollinia are encapsulated by the anther cap and so cannot come into contact with the stigma of another flower. Here, too, germination tests of the female pollen were positive. It is suspected that selfing of the female flowers here also will result in viable seeds. In both cases the female flowers are true hermaphrodites, but because of their limited male function one should think of them as functional female flowers. Male flowers, however, do not develop precursors of ovules, and a stigma is not present. Given the different flower morphologies and the pollination processes, one assumes that the floral fragrances should differ among the sexes of Catasetum flowers. The battered pollinator will remember the negative experience with the male flowers. So different fragrances in the female flowers would be the way out of this dilemma. Floral fragrances of five Catasetum species and two Cycnoches species were investigated by gas chromatography. Only weak differences in the fragrance composition of the separate sexes were detected, begging several questions. What are the forces driving the pollinator from male to female flowers? Is the weight of the pollinarium sufficient to explain avoidance of the male flowers? Does the bee still remember the disagreeable episode? Is identification effected only by visual senses?

Chromosome numbers and karyotypes of Catasetum species (Orchidaceae)

Mitotic chromosomes of 12 species of Catasetum were assessed to contribute with the karyotypic study of the subtribe Catasetinae (Orchidaceae), expanding the knowledge of this group in terms of chromosomes and supporting its taxonomic and evolutionary analysis. The species are maintained in cultivation in the greenhouse of the Department of Plant Biology/IB/UNICAMP and in the “Orquidário Frederico Carlos Hoehne” of the Botanical Garden of São Paulo. Chromosome counts ranged from 2n = 54 to 2n = 108. Karyotypes were prepared for all species studied, in which there was a predominance of metacentric chromosomes and some submetacentric ones. The chromosome size ranged from 0.5 to 4.9 μm, the total chromosome length ranged from 34.7 to 78.7 μm and the asymmetry index TF% ranged from 21.2 to 42.3. The results obtained so far favor the taxonomy of the genus, allowing to distinguish species with very similar external morphology.

A NEW SPECIES OF CATASETUM (ORCHIDACEAE) FOR THE STATE OF MATO GROSSO, BRAZIL

A new species of Catasetum Rich. ex Kunth (Orchidaceae), Catasetum apolloi Benelli & Grade, from the municipality of Carlinda in the State of Mato Grosso, Brazil is described and illustrated. The plant was discovered in a pasture near the Teles Pires River growing epiphytically under the palm Maximiliana regia Mart. A discussion and consideration of possible related species is presented.

A New Catasetum Species (Catasetinae, Orchidaceae) from Goias, Brazil

A new Catasetum species from Brazil,Catasetum confusum, is described and illustrated. This widely cultivated species had been referred previously toCatasetum ornithoides Pabst.

Sexual Dimorphism in Catasetum Orchids: Forcible Pollen Emplacement and Male Flower Competition

Orchids of the Neotropical genus Catasetum have sexually dimorphic flowers; that is, male and female flowers are distinctly different in shape and color. Male flowers forcibly attach a large pollinarium onto euglossine bees. Euglossa bees leave the male flower in response to pollinarium emplacement by Catasetum ochraceum and subsequently avoid male but not female flowers. This evidence suggests that sexual dimorphism promotes pollination. The aversion of the bee to pollinarium attachment and its avoidance of male flowers thereafter apparently reflect competition among male flowers that probably evolved concurrently with sexual dimorphism. Among Catasetum species, the extent of dimorphism is correlated with the degree of apparent aversion caused by the male flower (weight of the pollinarium). Thus, aversive pollinarium emplacement can account for widespread sexual dimorphism in Catasetum and for interspecific variations in its expression.

Resupination Studies of Flowers and Leaves

The torsion performed by zygomorphic flowers borne on pendulous racemes-such as Wistaria, Laburnum, &c.-is described and examples are given of the torsions which such zygomorphic flowers will exhibit if normally erect spikes are turned vertically downwards or normally pendent ones tied erect. An account is given of orchid flowers which normally are non-resupinate—species of Epidendrum, &.—and of those which are resupinate and of the further torsions which are involved when inflorescences bearing resupinate flowers are pendent. The torsions exhibited are illustrated by reference to the pendulous racemes of Cycnoches and to the flowers of Mormodes tigrina. The complete inversion of the flowers of Malaxis, which thus become ‘nonresupinate’, is mentioned and a full account of the similar inversion of the flowers of Angraecum eburneum is given, where the complicated torsions in three different planes result in a torsion through 630°. The leaf torsions of Bomarea, Luzuriaga, Pharus, and Leptaspis, where the morphologically lower side of the leaf becomes the upper surface owing to the twisting of the petiole, is described and an account is given of the two different types of pitcher in Nepenthes—those of the climbing stems being reversed owing to the twisting of their petioles. The physiological state into which the pitcher plant appears to pass when it reaches the adult condition, is compared with the production of Tree Ivy, which is propagated from the short, flowering shoots of the climbing plant. My thanks are due to Dr. C. R. Metcalfe for his assistance in examining the anatomy of the leaves of Leptaspis and Luzuriaga; to Mr. L. Stenning and Mr. W. E. Everett for their help in connexion with the orchid studies; to Miss Ross-Craig and Mr. G. Atkinson for their drawings, and to Mr. S. F. Ormsby for taking numerous photographs to show the twisting of the flower buds of Angraecum eburneum and other plants which have been reproduced as drawings for the text figures. Mr. V. S. Summerhayes kindly furnished me with the particulars relating to the Merent species of Catasetum and other orchids.