RESUMO
Leaf glands are found in many Rhamnaceae species, the buckthorn family, and are frequently used in taxonomic studies of the group, especially because they are easily visible to the naked eye. Despite the many records and extensive use in the taxonomy of the family, few studies deal with the classification of these glands and their roles for the plant. Thus, this study aimed to unravel the type, functioning, and putative functions of the leaf glands of three Brazilian forest species: Colubrina glandulosa Perkins, Gouania polygama (Jacq.) Urb., and Rhamnidium elaeocarpum Reissek. Leaves were collected and processed for surface, anatomical, histochemical, and ultrastructural analyses. In addition, the presence of visitor animals was registered in the field. The leaf glands of C. glandulosa and G. polygama are defined as extrafloral structured nectaries due to their anatomical structure, interaction with ants, and the presence of reduced sugars and of a set of organelles in the secretory cells. The unusual mechanism of nectar release and exposure in an apical pore stands out in G. polygama. The glands of R. elaeocarpum are ducts or cavities that secrete phenolic oil resin. Their presence is an atypical condition in the family, although they are often confused with mucilage reservoirs, much more common in Rhamnaceae. The extrafloral nectary, secretory cavity, and duct are associated with plant protection against phytophages, either by attracting patrol ants or by making the organs deterrent. Our data, combined with other previously obtained data, attest to the great diversity of gland types found in Rhamnaceae species.
RESUMO
Psychotria viridis Ruiz & Pav (Rubiaceae) occurs naturally throughout the Amazon and it is traditionally used by indigenous communities, being incorporated into religious use in urban contexts over the last few decades. It is known and cultivated in many regions of South America for possessing valuable bioactive alkaloids. In this paper, we described P. viridis leaf morphology, anatomy and histochemistry from three populations cultivated in the southeastern Brazil, in order to identify possible adaptations to local environment and management. All plants presented terminal stipules and basic morpho-anatomical patterns of leaves, consistent with most species of the genus, as heterogeneous dorsiventral mesophyll, uniseriate epidermis, presents large cells with prominent vacuoles and druses. Unicellular non-glandular trichomes and multicellular starry trichomes were present in the primary and secondary veins. Amphi-hypostomatic leaf pattern, not yet described for the species, was common in all studied plants. Variation in the presence of domatia in the same population indicates that this structure cannot be used for taxonomic determination of P. viridis, as already described for other species of the genus. Presence of secretory ducts and reduction in stomata density and leaf area represent the main morpho-anatomic adaptations of plants from drier and warmer climates. Histochemical tests were positive for alkaloids, polysaccharides, proteins and phenolic compounds, being negative for starch only in plants subjected to water stress. We concluded that the morpho-anatomical and histochemical alterations found in the plants of this study resulted from seasonal water deficit adaptations and to maintain or attract mutualistic organisms
Assuntos
Banisteriopsis/anatomia & histologia , Banisteriopsis/citologia , Banisteriopsis/química , Imuno-HistoquímicaRESUMO
Psychotria viridis Ruiz & Pav (Rubiaceae) occurs naturally throughout the Amazon and it is traditionally used by indigenous communities, being incorporated into religious use in urban contexts over the last few decades. It is known and cultivated in many regions of South America for possessing valuable bioactive alkaloids. In this paper, we described P. viridis leaf morphology, anatomy and histochemistry from three populations cultivated in the southeastern Brazil, in order to identify possible adaptations to local environment and management. All plants presented terminal stipules and basic morpho-anatomical patterns of leaves, consistent with most species of the genus, as heterogeneous dorsiventral mesophyll, uniseriate epidermis, presents large cells with prominent vacuoles and druses. Unicellular non-glandular trichomes and multicellular starry trichomes were present in the primary and secondary veins. Amphi-hypostomatic leaf pattern, not yet described for the species, was common in all studied plants. Variation in the presence of domatia in the same population indicates that this structure cannot be used for taxonomic determination of P. viridis, as already described for other species of the genus. Presence of secretory ducts and reduction in stomata density and leaf area represent the main morpho-anatomic adaptations of plants from drier and warmer climates. Histochemical tests were positive for alkaloids, polysaccharides, proteins and phenolic compounds, being negative for starch only in plants subjected to water stress. We concluded that the morpho-anatomical and histochemical alterations found in the plants of this study resulted from seasonal water deficit adaptations and to maintain or attract mutualistic organisms(AU)
Assuntos
Banisteriopsis/anatomia & histologia , Banisteriopsis/química , Banisteriopsis/citologia , Imuno-HistoquímicaRESUMO
Discrepant and incomplete interpretations of fruits of Pterodon have been published, especially on the structural interpretation of the pericarp portion that remain attached to the seed upon dispersal. The present work clarified these doubts and analyzed ultrastructural aspects of the Pterodon emarginatus diaspores using light and transmission electron microscopes. Cell divisions are prevalent among the initial phases of development, and the subadaxial and adaxial meristems form the fibrous inner mesocarp and the endocarp composed of multi-seriate epidermis, respectively. At the median mesocarp, numerous secretory ducts differentiate between the lateral bundles, by lytic process. After lysis of the central cells and the formation of the lumen, the ducts show unistratified secretory epithelium with dense cells; oil droplets are observed on the secretory epithelium and the subadjacent tissues. At maturity, the uniseriate exocarp and the outer mesocarp slough off in an irregular fashion, leaving the diaspore composed of a papery and brittle wing linked to a seed chamber that includes the median mesocarp composed of lignified cells, bordering vascular bundles and many secretory ducts whose epithelial cells develop large vacuoles that accumulate oleoresins. The Pterodon emarginatus fruit is a cryptosamara.
Interpretações discrepantes e incompletas têm sido conferidas ao fruto de Pterodon, especialmente no que tange à determinação estrutural da porção pericárpica que acompanha a semente na dispersão. Assim, com o objetivo de dirimir tais dúvidas e analisar a organização ultra-estrutural das estruturas secretoras presentes no diásporo de Pterodon emarginatus, realizaram-se estudos convencionais aos microscópios de luz e eletrônico de transmissão. Nas fases iniciais de desenvolvimento do fruto, prevalecem divisões celulares; pela ação do meristema subadaxial e do adaxial, formam-se, respectivamente, o mesocarpo interno fibroso e o endocarpo composto por epiderme multisseriada. No mesocarpo mediano, entre os feixes vasculares laterais, diferenciam-se numerosos ductos secretores lisígenos. Após a lise das células centrais e formação do lume, os ductos apresentam epitélio secretor uniestratificado, com células densas; gotas de óleo são observadas no epitélio secretor e tecido subjacente. Na maturidade, o exocarpo unisseriado e o mesocarpo externo, ambos fenólicos, descamam irregularmente, sendo o diásporo constituído pela ala papirácea e quebradiça, ligada ao núcleo seminífero que abrange o mesocarpo mediano de células lignificadas, margeando feixes vasculares e muitos ductos secretores, que apresentam acúmulo de oleorresina e cujas células epiteliais tornam-se vacuoladas. O fruto de Pterodon emarginatus é, portanto, uma criptossâmara.