Characters of the gynoecium are considered potentially significant for the systematics of Myrtaceae. However, only two such characters – ovule number and placentation – have been addressed from an evolutionary perspective. Colleter presence in flowers is a synapomorphy of Myrtales; however, no morphological and histochemical descriptions of such structures have been done in Myrtaceae. Here we analysed the ontogeny and anatomy of the gynoecium combined with the ontogeny, anatomy, ultrastructure, and histochemistry of the colleters to study the evolution of these characters and map their states in the Myrteae phylogenetic tree. Our findings may help elucidate the evolutionary history of this tribe of fleshy-fruit producers so important towards maintaining ecological balance in the rainforest. Floral anatomy and ontogeny were analysed using light microscopy. Colleter samples were processed using standard methods for light and transmission electron microscopy. The main metabolites in colleters were detected via histochemistry. To map character states the program Mesquite version 2.71 was used. The morphological characters of the South American Myrteae here analysed provided an overview of the evolution of gynoecium – with cauline or carpellate placenta – and of colleters, as well as synapomorphies for the clades Plinia + Myrcia and Eugenia + Pimenta. The presence of two integuments in the ovules associated with sclereids and colleters in the gynoecium and the young fleshy fruit assures the efficient dispersal of their seeds. Our findings regarding gynoecium structural diversity of the tribe Myrteae give a new insight on their morphologically uniform flowers.

ABSTRACT(Mucilage-secreting structures of Hibiscus pernambucensis Arruda (Malvaceae): distribution, morphoanatomical and histochemical characterization). This work studied the mucilage-secreting structures of Hibiscus pernambucensis using light and scanning electron microscopy. Known as guaxima-do-mangue, algodão-do-brejo and embira-do-mangue, this species is a native shrub that occurs in mangrove and restinga along the Brazilian coast, and is important in the production of textile fibers and cellulose, provides abundant mucilage that is used medicinally like other Malvaceae species, and has tannins. The results of this work found colleters, pearl glands, long-stalked secretory trichomes, ducts, cavities and idioblasts. The colleters occur on the shoot apices, stipules, leaf primordia, leaves, young sepals and petals. The pearl glands are present in the adaxial and abaxial surface of the leaf primordia. The ducts and the cavities occur in the vegetative and reproductive shoot apices. The idioblasts occur in the roots, both in primary and secondary stages of development, and in the leaf mesophyll. The secretion of the different secretory structures is made predominantly of acids and neutral polysaccharides, proteins, lipids and phenolic substances. The presence of external and internal mucilage-secreting structures in all plant organs, at different stages of development, represents an important adaptive mechanism to restinga and mangrove environments.

Resumo Malvaceae possui grande diversidade morfológica de estruturas secretoras, que por sua vez apresentam importância ecológica e taxonômica. Entretanto até o momento não foram encontrados registros de estudos sobre as estruturas secretoras em Pavonia alnifolia A.St.-Hil., uma espécie ameaçada de extinção, endêmica de restingas do Rio de Janeiro e Espírito Santo. No presente estudo são apresentados dados anatômicos e histoquímicos das estruturas secretoras da referida espécie. O material foi coletado na Restinga da Marambaia - Rio de Janeiro e processado de acordo com técnicas usuais para estudos de anatomia e histoquímica. A análise dos resultados mostrou a presença de canais, cavidades, idioblastos e tricomas secretores de mucilagem; idioblastos de substâncias fenólicas e lipídicas, além de nectários florais. As secreções produzidas por estas estruturas representam um papel potencialmente importante para adaptação da espécie ao ambiente de restinga, estando envolvidas na manutenção de interações com insetos visitantes, o que constitui relevante modelo para realização de estudos experimentais com abordagem ecológica.

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JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range of content in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new forms of scholarship. For more information about JSTOR, please contact support@jstor.org.. The University of Chicago Press is collaborating with JSTOR to digitize, preserve and extend access to International Journal of Plant Sciences.Garcinia brasiliensis Mart., a species from the Amazon and Atlantic rainforests, is cryptic dioecious because the morphologically perfect flowers are in fact pistillate given the absence of pollen. The flowers present diurnal anthesis, have a sweet and mild scent, and are pollinated by bees in search of the nectar secreted by evident nectaries. The flowers of Clusiaceae bear nectaries of staminodial origin. In Garcinia, the nectaries have been interpreted as being of receptacular origin or as sterile reproductive organs. Our aim in this study was to analyze the nature of the indefinite perianth, the differential development of the androecium in relation to the sexual system, and the origin of the nectaries from the perspective of floral biology and evolution. Floral anatomy and ontogeny were analyzed using both LM and SEM. The species has bracteoles that surround the flower buds. The perianth consists of tepals that are very similar to the bracteoles and that show a centripetal and gradual decrease of mesophyll and cuticle thickness. Developmental irregularities in the anthers lead to a reduction of pollen production in staminate flowers and complete male sterility in pistillate flowers because of peri-and postmeiotic cell degeneration. Both floral forms have nectaries, the origin of which we discuss, leading to hypotheses about their nature.

Paullinia é um gênero monofilético de lianas com distribuição neotropical, abrangendo aproximadamente 220 espécies. No Brasil, existem 102 espécies ocorrendo principalmente nos domínios fitogeográficos da Mata Atlântica e Amazônia. As espécies deste gênero possuem diversos usos como psicotrópicos, bactericidas, antioxidantes, venenos de peixes, estimulantes e para fins ritualísticos. O gênero é, no entanto, pouco estudado do ponto de vista anatômico e histoquímico. No presente estudo, foram feitas investigações morfoanatômicas e histoquímicas das folhas de Paullinia dasygonia Radlk., P. micrantha Cambess. e P. trigonia  Vell. As espécies estudadas possuem caracteres foliares muito semelhantes, o que dificulta sua identificação. As folhas apresentam estrutura dorsiventral, apresentam feixes vasculares colaterais e tricomas tectores e glandulares que variam nas espécies quanto à forma, comprimento e distribuição. Os tricomas glandulares possuem polissacarídeos neutros e compostos fenólicos. Além disso, foram observados laticíferos contendo gotículas lipídicas, alcalóides, proteínas e compostos fenólicos em diversas regiões da folha. As saponinas, características da família, foram observadas nos tricomas secretores e geralmente no mesofilo e nervura central. Os resultados obtidos fornecem evidências que justificam a investigação farmacológica dessas três espécies, bem como outras do gênero.