Scielo RSS <![CDATA[Acta Botanica Brasilica]]> vol. num. AHEAD lang. en <![CDATA[SciELO Logo]]> <![CDATA[Secretory spaces in species of the clade Dipterygeae (Leguminosae, Papilionoideae)]]> ABSTRACT Dipteryx, Pterodon and Taralea are legume genera known for secreting oils, produced in secretory canals and cavities, with medicinal properties. We analyzed the distribution, morphology and histochemistry of these glands in leaves and stems of Dipteryx alata, Pterodon pubescens and Taralea oppositifolia, three Neotropical species, using standard techniques for anatomy and histochemistry. Secretory spaces, i.e. secretory cavities and canals, exhibited a wide lumen and a single layer of epithelium. Digitiform epithelial cells, forming trabeculae protruding into the lumen, were seen in all three species. Secretory cavities with a rounded or oval lumen and secretory canals with an elongated lumen in longitudinal sections were found only in T. oppositifolia. In D. alata and P. pubescens, only secretory cavities were found. In P. pubescens, secretory cavities occurred in the leaf blade margin. In T. oppositifolia, secretory spaces were much more numerous than in the other two species. Terpenes, total lipids, phenolic compounds, alkaloids and polysaccharides were detected in the secretory spaces of the three species. The abundance of secretory spaces, the presence of canals in T. oppositifolia and the position of cavities in P. pubescens are features with potential diagnostic value for their respective genera. <![CDATA[Beyond pollination: diversity of secretory structures during flower development in different legume lineages]]> ABSTRACT Floral secretory structures are usually associated with the attraction of pollinators, but may also play an important role in the mechanisms of plant protection. This study aimed to show the diversity of secretory structures present in the developing flowers of 15 legume species belonging to different clades and to associate them with functions other than the pollinator attraction. Buds, flowers and developing axis of inflorescence were processed for surface, histological, and ultrastructural analyses. The species investigated displayed a wide diversity of secretory structures in developing flowers such as phenolic cells and/or tissues, mucilaginous cells, secretory cavities, secretory trichomes and colleters. Each type of secretory structure exhibited variation in morphology and location in the flower and/or axis of inflorescence depending on the species. Special mucilage cells, secretory cavities, secretory trichomes and colleters have great potential for comparative morphological studies due to their diversity of forms or restricted occurrence to certain taxa, contributing to a more robust morphological data base for the new clades emerging in Leguminosae. The scarcity of reports about floral secretory structures of Leguminosae seems to be more related to deficient sampling than to the absence of such structures in the group, which highlights the need for further investigation. <![CDATA[Trichomes that secrete substances of a mixed nature in the vegetative and reproductive organs of some species of Moraceae]]> ABSTRACT This study aimed to obtain new information about the distribution, morphology and content of secretory trichomes present in the vegetative and reproductive organs of four species of Moraceae: Artocarpus heterophyllus, Dorstenia cayapia, Maclura tinctoria and Sorocea bonplandii. Stem, leaf, flower and inflorescence samples were processed for scanning electron and light microscopy. The species have secretory trichomes on the leaf blade, petiole and stem and also on the inflorescence and flowers of D. cayapia and S. bonplandii and on the peduncle of the inflorescence in A. heterophyllus. These trichomes are of the capitate type in all species, but A. heterophyllus also possess peltate secretory trichomes. Both trichome types exhibit a multicellular head and a unicellular peduncle. Peduncle size and head cell number varies according to species. Peltate trichomes located in depressions were found only in species of Artocarpus, and so should be of diagnostic value for the genus. In all species the trichomes secrete polysaccharides, alkaloids and lipids; phenolic compounds occur in A. heterophyllus and M. tinctoria trichomes. These trichomes probably act in the protection against herbivores, pathogens, desiccation and/ or UV radiation. Moreover, the trichomes found in the inflorescence of D. cayapia may exert a function in pollen grain adhesion. <![CDATA[Colleters in <em>Chamaecrista</em> (L.) Moench sect. <em>Chamaecrista</em> and sect. <em>Caliciopsis</em> (Leguminosae-Caesalpinioideae): anatomy and taxonomic implications]]> ABSTRACT The genus Chamaecrista contains ca. 330 species organized into six sections, of which section Chamaecrista is the second largest (ca.75 species) distributed among six series, while the section Caliciopsis contains only two species. Colleters have been described in the genus Chamaecrista and they show potential taxonomic and phylogenetic significance. They are associated with lubrication, desiccation prevention and protection from microbial attacks of young developing organs. Although six types of colleters have been described for the genus Chamaecrista, there have been no studies focusing on the diversity of colleters in the sections Chamaecrista and Caliciopsis. Samples from developing leaves and flowers of both sections were obtained from herbarium and field collections and subjected to standard methodologies for both light and scanning electron microscopy. Histochemical tests were also performed to determine the nature of the exudates. Five types of non-vascularized colleters were found: short digitiform, long digitiform, club-shaped, pyriform and short bottle-shaped. Polysaccharides, pectins, lipids and proteins were detected in the exudates of all types of colleters. Among the five types of colleters observed, pyriform is a novelty for Chamaecrista, reinforcing the significant morphological diversity of these secretory structures in this genus. <![CDATA[Are stem nectaries common in Gentianaceae Juss.?]]> ABSTRACT Extrafloral nectaries (EFNs) are specialized structures that produce and release nectar and are located on leaves, cotyledons and, more seldomly, stems. Peculiar leaf nectaries have been described for thirty-three Neotropical species of Gentianaceae, while stem nectaries have been reported for only nine. The aim of this study was to verify the occurrence of stem EFNs within Gentianaceae and investigate the existence of a correlation between their occurrence and the geographical distribution of species. Samples of internodal regions from field and herbarium specimens were submitted to standard light microscopy techniques. Data regarding the geographical distribution of species were acquired from herbarium specimens and the literature. A total of 37 species were investigated, representing 25 genera distributed among five tribes. Nectaries, composed of modified epidermal cells, were observed in 16 species restricted to the Neotropical tribes Helieae, Saccifolieae, Potalieae and Coutoubeinae; exceptions were Cicendia quadrangularis and Zygostigma australe, which both occur in the Neotropics but do not possess EFNs. These results demonstrate that stem EFNs are common among Neotropical taxa of Gentianaceae, and are typically absent from taxa in temperate regions. <![CDATA[Outer cell wall structure and the secretion mechanism of colleters of <em>Bathysa nicholsonii</em> K. Schum. (Rubiaceae)]]> ABSTRACT Secretory structures are formed by many types of plants and are present on numerous different organs. Among the many types of known secretory structures, colleters are predominant on plants of the Rubiaceae. One remarkable characteristic of secretory tissues is the export of exudates; however, the precise mechanism involved in this process is still unclear. To better understand the mechanisms of exudate externalization it is necessary to understand the ultrastructure and dynamics of the outer cell wall of the secretory structures during the secretory process, and so we investigated these aspects of the colleters of Bathysa nicholsonii. The outer cell wall (OCW) exhibits multiple layers: a basal polysaccharide rich layer; a cuticular membrane, which is subdivided into arborescent and reticulated layers; and a thin cuticle proper. The structural organization of the OCW is changed during secretion passage, which is mainly related to the development of a secretion accumulation site on the polysaccharide rich layer. Secretion dynamics is driven by the organization and disruption of the secretion accumulation site. The results show that the OCW of the colleters of B. nicholsonii is a dynamic structure with an active role in secretion externalization via constant structural reorganization directly related to secretion passage. <![CDATA[Different physiological responses under drought stress result in different recovery abilities of two tropical woody evergreen species]]> ABSTRACT The effects of water deficit on physiological and biochemical variables of young plants of two tropical woody species, Pachira aquatica and Sterculia foetida, and their recovery abilities were measured. Leaf water potential, gas exchange and selected carbon metabolism components were measured in a greenhouse experiment with control, moderate and severe water deficit treatments. Under severe drought stress, gas exchange and chlorophyll fluorescence decreased in both species compared to their respective controls. After rehydration, P. aquatica and S. foetida showed a partial and full recovery of the measured variables, respectively. In addition, a decrease and an increase in photosynthetic pigments were observed for P. aquatica and S. foetida, respectively, compared to their controls. In conclusion, the two species showed differing responses regarding photosynthetic pigment content dynamics for tolerating water deficit. Individuals of P. aquatica in the severe water deficit treatment showed a decrease in pigments, which may have impaired the recovery of metabolism (gas exchange) after rehydration, while S. foetida experienced an increase, favoring a full recovery of gas exchange and biochemical metabolism after rehydration. <![CDATA[Phytoremediation of arsenic-contaminated water: the role of antioxidant metabolism of <em>Azolla caroliniana</em> Willd. (Salviniales)]]> ABSTRACT Phytoremediation has proven to be an efficient technology for removing arsenic (As) from water, but the plants used in this process need to be tolerant to the damage caused by As. The toxic effect of As on growth and functioning of the antioxidant system was studied in individual plants of Azolla caroliniana exposed to five concentrations of As (0.0, 0.25, 0.5, 1.0 and 1.5 mg L-1) for the course of five days. Growth, As absorption, enzymatic activity, total and non-protein thiols and anthocyanin content were assessed. Azolla caroliniana was able to take up large amounts of the pollutant, reaching As concentrations of 386.1 µg g-1 dry weight without saturating the absorption mechanism. The tolerance index and the growth of A. caroliniana decreased with the increased As uptake. Superoxide dismutase, peroxidases, catalases and glutathione reductase activities increased at lower doses of As and subsequently declined with higher concentrations, whereas ascorbate peroxidase activity was reduced in all treatments. Unlike the enzymatic defence system, anthocyanin and thiol content increased consistently in all treatments and showed a positive correlation with As concentration. Therefore, the increased synthesis of non-enzymatic antioxidants is most likely the main factor responsible for the high As tolerance of A. caroliniana. <![CDATA[Floristic and ecological characterization of habitat types on an inselberg in Minas Gerais, southeastern Brazil]]> ABSTRACT Inselbergs are granitic or gneissic rock outcrops, distributed mainly in tropical and subtropical regions. They are considered terrestrial islands because of their strong spatial and ecological isolation, thus harboring a set of distinct plant communities that differ from the surrounding matrix. In Brazil, inselbergs scattered in the Atlantic Forest contain unusually high levels of plant species richness and endemism. This study aimed to inventory species of vascular plants and to describe the main habitat types found on an inselberg located in the state of Minas Gerais, in southeastern Brazil. A total of 89 species of vascular plants were recorded (belonging to 37 families), of which six were new to science. The richest family was Bromeliaceae (10 spp.), followed by Cyperaceae (seven spp.), Orchidaceae and Poaceae (six spp. each). Life forms were distributed in different proportions between habitats, which suggested distinct microenvironments on the inselberg. In general, habitats under similar environmental stress shared common species and life-form proportions. We argue that floristic inventories are still necessary for the development of conservation strategies and management of the unique vegetation on inselbergs in Brazil. <![CDATA[Updating the list of chromosome numbers for <em>Philodendron</em> (Araceae)]]> ABSTRACT Aiming for a better understanding of karyotype evolution within Philodendron, we report chromosome counts for 23 species of the genus, of which 19 are being reported for the first time, thus increasing to 84 ( ca. 17 % of the genus) the total number of species with available chromosome counts. The diploid numbers 2 n = 32 and 2 n = 34 were the most common, with 10 and 11 species, respectively, whereas only two species presented different chromosome numbers ( P. giganteum with 2 n = 30 and P. adamantinum with 2 n = 36). The results are discussed in the context of previous analyses of karyotypes of Philodendron spp., taking into account bidirectional dysploidy as the main mechanism of chromosome number evolution within the genus. <![CDATA[Spore germination and young gametophyte development of the endemic Brazilian hornwort <em>Notothylas vitalii</em> Udar & Singh (Notothyladaceae - Anthocerotophyta), with insights into sporeling evolution]]> ABSTRACT Notothylas vitalii is an endemic Brazilian hornwort species, easily identified by the absence of pseudoelaters and columella, and the presence of yellow spores. Plant material was collected in Recife, Brazil, and the spores were sown onto Knop’s medium, germinating after thirty days only with the presence of light. Germination occurred outside the exospore, and only after the walls had separated into three or four sections did a globose sporeling initiate its development. Following longitudinal and transversal divisions, the initial loose mass of cells became a thalloid gametophyte, subsequently developing into a rosette-like juvenile thallus with flattened lobes. Additional information concerning sporeling types in key genera of hornworts, such as Folioceros and Phymatoceros, will be crucial for inferring the possible ancestral type and the evolution of this trait among hornworts. Our study supports the necessity of supplementary studies on sporeling development, combined with morphological and phylogenetic investigations, to help elucidate the evolution of the Anthocerotophyta and their distribution patterns. <![CDATA[Metabolic responses and β-carotene production by the unicellular green alga <em>Dunaliella salina</em> exposed to leaf extracts]]> ABSTRACT The present work investigated the effects of aqueous extracts of eucalyptus ( Eucalyptus globulus) and elderberry ( Sambucus ebulus) leaves on β-carotene productivity in Dunaliella salina, a green microalga. Leaf extracts from eucalyptus have greater amounts of phenolics and flavonoids, as well as greater ferric reducing antioxidant potential than elderberry. The extracts of both species greatly inhibited growth of algal suspensions. However, chlorophyll and β-carotene concentration increased in cells treated with leaf extracts, and the highest values were detected in 1 % eucalyptus and 2 % elderberry extracts. Fresh weight, total sugar, and protein content significantly increased following exposure of cells to different doses of leaf extracts. However, in doses containing more than 2 % eucalyptus, the upward trend for total sugar and protein ceased and remained statistically unchanged. These results suggest that metabolic modifications enable D. salina cells to tolerate the stress induced by the leaf extracts through allocating carbon flux to the synthesis of osmolytes and putative antioxidant molecules (e.g. sugars and β-carotene). Therefore, the use of leaf extracts holds potential to be a promising and effective way to improve D. salina cultivation for β-carotene production and other biotechnological and industrial applications. <![CDATA[Temporal evaluation of the Conservation Priority Index for medicinal plants]]> ABSTRACT We investigated, through a temporal comparison, the extraction of non-timber forest resources by quantitatively analyzing the Conservation Priority Index (CPI). The study focused on the Fulni-ô Indigenous Territory, in the municipality of Águas Belas, PE (Northeast Brazil), which is characterized by caatinga vegetation (seasonal dry forest). Information on the availability of the exploited resources and the reported use of the species were obtained from vegetation sampling and semi-structured interviews, respectively. Our results demonstrated a reduction in species richness overtime, which may be due to continued resource extraction in the area, and that some species with low densities were even more affected. The species reported as being at high risk in the current study apparently did not differ from their status in the previous study, which supports the idea that these species are most evident in this situation more for their high potential of use than for their high densities. When we associate these events together with the disappearance of some rare species, we can conclude that the CPI was not efficient in predicting changes, and that the combination of variables used with the biological variables of the species needs to be adjusted. <![CDATA[Allelopathic suppression by <em>Conyza canadensis</em> depends on the interaction between latitude and the degree of the plant’s invasion]]> ABSTRACT Allelopathic suppression of the growth of co-occurring plant species in invaded ecosystems is an important factor in some plant invasions. This study uses leaf extracts of the invasive plant species Conyza canadensis to determine its allelopathic effects along a latitudinal gradient, and under different cover classes and degrees of invasion, on seed germination and growth of Lactuca sativa, a sensitive bioindicator of allelochemicals. The allelopathic effects of C. canadensis on seedling height, root length, seedling biomass, germination percentage, germination potential, germination index, germination rate index, and vigor index of L. sativa increased significantly with increasing latitude. A possible explanation is that the leaves of plants growing in high latitudes secrete a higher concentration of allelochemicals than do leaves of plants growing in low latitudes. The allelopathic effects of C. canadensis on seedling height, seedling biomass, germination potential, germination index, germination rate index, and vigor index of L. sativa decreased with increasing degree of invasion. The more intense allelopathic effects of C. canadensis at lower degrees of invasion may enable it to establish populations in ecosystems by inhibiting the seed germination and growth of co-occurring species. <![CDATA[Elaiophores: their taxonomic distribution, morphology and functions]]> ABSTRACT Elaiophores are floral glands that secrete non-volatile oils as a reward for their pollinators. Their secretions mediate a specialized interaction between oil-producing plants and a few species of oil-collecting bees - Apidae and Melittidae. The present review focuses on the morphological and functional aspects of these secretory structures. We also provide information on their chemistry and pollination ecology. Our survey is organized taxonomically among the plant families for which elaiophore occurrence has been confirmed -for the monocots, Iridaceae and Orchidaceae, and for the eudicots, Calceolariaceae, Cucurbitaceae, Krameriaceae, Malpighiaceae, Plantaginaceae, Primulaceae, Scrophulariaceae, Solanaceae and Stilbaceae. Most oil flowers are zygomorphic, bisexual, nectarless and present their elaiophores on the protective whorls or on the androecium. Trichomal elaiophores are reported in all of these families except Krameriaceae and Malpighiaceae, and they vary in the density and morphology of the trichomes. Epithelial elaiophores occur in some monocot representatives and in Krameriaceae and Malpighiaceae, and are similar among species. An intermediate type of elaiophore is reported in some species of Orchidaceae. Regardless of elaiophore type, these glands have similar subcellular features and secretion-release mechanisms. Finally, we note the dearth of information on elaiophore ultrastructure and functioning for several plant families. <![CDATA[A reduced, yet functional, nectary disk integrates a complex system of floral nectar secretion in the genus <em>Zeyheria</em> (Bignoniaceae)]]> ABSTRACT The genus Zeyheria (Bignoniaceae) comprises only two species, both of which have been described as possessing a reduced and non-functional nectary disk. Despite the importance of this evolutionary change in the floral nectary, these functional assumptions have been based on disk size and on the distribution, abundance and histochemistry of corolla-borne trichomes. By combining methods on light and electron microscopy, here we investigated the functionality of the reduced nectary disk and describe all of the tissues and structures of the nectar chamber in order to determine the sites of floral nectar secretion in both Zeyheria species. . Our data find the floral nectary traits of both species to be very similar, although differing in their cellular contents. Subcellular evidence in both species indicated that disk, stipe and petal axils were, predominantly, involved in hydrophilic secretion, while capitate glandular trichomes produced lipophilic secretion and papillae produced mixed secretion. Our study shows that in spite of its reduced size, the reduced disk functions in nectar secretion in both species of Zeyheria. This kind of nectary system is a novelty for Bignoniaceae, since it comprises several tissues and structures functioning in an integrated fashion. <![CDATA[Pericarp ontogeny of <em>Tapirira guianensis</em> Aubl. (Anacardiaceae) reveals a secretory endocarp in young stage]]> ABSTRACT Most species of Anacardiaceae have drupes containing secretory structures.. The substances produced by these structures may have importance to industry and folk medicine, and may even cause allergenic effects. This work describes the ontogeny of pericarp of Tapirira guianensis with an emphasis on the secretory structures present at different stages of development. Ovary and fruits in various stages of development were collected, fixed and processed for studies using light and scanning electron microscopy according to conventional techniques. Histochemical tests were employed to identify the major metabolites present in the tissues. The fruit is a drupe formed by exocarp, mesocarp containing secretory ducts and idioblasts, and endocarp with some lignified layers. Fruit growth occurs through the division and elongation of cells. The secretory ducts produce mainly phenols and lipids and are active during all stages of development. The secreted substances protect the fruit against pathogens and predators. In ripe fruits the cells of the mesocarp accumulate starch. This study is the first report of the presence of a secretory endocarp in young fruits of a species of Anacardiaceae. The substances produced by the endocarp in early developmental stages may play an important role in seed dispersal and germination. <![CDATA[Morphology and histochemistry of glandular trichomes in <em>Hyptis villosa</em> Pohl ex Benth. (Lamiaceae) and differential labeling of cytoskeletal elements]]> ABSTRACT Lamiaceae contains many species known for their aromatic properties that are produced by the production of essential oils in glandular trichomes. Hyptis is one of the most common genera of Lamiaceae in the Brazilian flora, and includes several species with medicinal value. However, studies on the morphology and functioning of their glandular trichomes are lacking. We analyzed the morphology, histochemistry and ultrastructure of the glandular trichomes in leaves of H. villosa, emphasizing the differential distribution of actin filaments and microtubules in cells secreting hydrophilic and lipophilic compounds. Four morphotypes of glandular trichomes were identified. Total lipid, terpenes, alkaloids, phenolic compounds, proteins and polysaccharides were histochemically detected in all morphotyes. This evidences the mixed nature of the secretions of this species, although there are differences in the prevalence of lipophilic and hydrophilic components among the glandular morphotypes and among the cells of the same trichome. The actin microfilaments are more abundant in cells that secrete mainly hydrophilic compounds, and microtubules predominate in cells that secrete lipophilic compounds. Our results corroborate the correlation between the glandular morphotype and the composition of the secretion produced, with a differential distribution of the cytoskeletal elements according to the prevalence of either hydrophilic or lipophilic substances.