Mucilage cells in the flower of Rosales species: reflections on morphological diversity, classification, and functions.

The presence of mucilage cells in plants, studied mainly in vegetative organs, is a condition shared by several taxonomic groups and aspects related to their diversity have been discussed with systematic purposes. This study explores the flower distribution and classification of mucilage cells in Rosales species, with inferences about flower functions. Floral buds from fifty-seven species representing seven of nine families recognized in the Rosales were sampled and processed for light and transmission electron microscopy. Mucilage cells were found in about 40% of the studied species of Cannabaceae, Rhamnaceae, Ulmaceae, and Urticaceae families, whereas no floral mucilage cells were found in species of Elaeagnaceae, Moraceae, and Rosaceae. Mucilage cells were found in the epidermis and internal tissues of many organs of different floral morph types. There is a great diversity of forms of presentation of mucilage in cells, from smaller individualized single cells to very bulky cells and to completely filled mucilage reservoirs. In some cases, cells with mucilage apparently in the cell wall and others with mucilage in the vacuole seem to occur side by side. This diversity challenges the existing classifications of mucilage cells and reinforces the importance of ontogenetic and ultrastructural studies following the path of mucilage in cells in order to propose a more natural classification and to elucidate the evolution of mucilage cells in plants.

New Aspects of Secretory Structures in Five Alismataceae Species: Laticifers or Ducts?

The secretory structures of Alismataceae have been described as secretory ducts, laticifer ducts, laticifer canals or schizogenous ducts. However, these terms are not found in the specialized literature, and ontogenetic analyses for the exact classification of these structures are missing. Accordingly, more studies regarding the secretory structures of Alismataceae are necessary to establish homology in the family or in the order. Thus, the aim of this study was to describe the anatomy, ontogeny, distribution in the organs and exudate composition of the secretory structures present in five Alismataceae species in order to determine whether the family has laticifers or secretory ducts. Samples of leaves, flowers and floral apices were processed for anatomical and histochemical analyses by light microscopy. The analysis indicated the presence of anastomosing secretory ducts in all species, occurring in both leaves and flowers. The exudate contains lipids, alkaloids, proteins and polysaccharides, including mucilage. The secretory duct structure, distribution and exudate composition suggest a defense role against herbivory and in wound sealing. The presence of secretory ducts in all species analyzed indicates a probable synapomorphy for the family.

Expanding the laticifer knowledge in Cannabaceae: distribution, morphology, origin, and latex composition.

Cannabaceae is a known family because of the production of cannabinoids in laticifers and glandular trichomes of Cannabis sativa. Laticifers are latex-secreting structures, which in Cannabaceae were identified only in C. sativa and Humulus lupulus. This study aimed to expand the knowledge of laticifers in Cannabaceae by checking their structural type and distribution, and the main classes of substances in the latex of Celtis pubescens, Pteroceltis tatarinowii, and Trema micrantha. Such information is also updated for C. sativa. Samples of shoot apices, stems, leaves, and flowers were processed for anatomical, histochemical, ultrastructural, and cytochemical analyses. Laticifers are articulated unbranched in all species instead of non-articulated as previously described for the family. They occur in all sampled organs. They are thick-walled, multinucleate, with a large vacuole and a peripheral cytoplasm. The cytoplasm is rich in mitochondria, endoplasmic reticulum, dictyosomes, ribosomes, and plastids containing starch grains and oil drops. Pectinase and cellulase activities were detected in the laticifer wall and vacuole, confirming its articulated origin, described by first time in the family. These enzymes promote the complete dissolution of the laticifer terminal walls. The latex contains proteins, lipids, and polysaccharides in addition to phenolics (C. sativa) and terpenes (C. pubescens, T. micrantha). The presence of laticifers with similar distribution and morphology supports the recent insertion of Celtis, Pteroceltis, and Trema in Cannabaceae. The articulated type of laticifer found in Cannabaceae, Moraceae, and Urticaceae indicates that the separation of these families by having distinct laticifer types should be reviewed.

Anatomia foliar de três espécies de Stylosanthes SW. e sua associação com a composição e formação potencial de fitobezoares em bovinos / Leaf anatomy of three species of Stylosanthes SW. and its association with the composition and formation potencial of phytobezoar in bovines

Fitobezoares são estruturas formadas pela agregação de fibras, principalmente vegetais, no trato digestivo de ruminantes, ocasionando obstruções intestinais que podem levar o animal à morte. Informações sobre a formação desse aglomerado ainda são escassas. Neste estudo, são identificados os principais componentes de fitobezoares bovinos, e descrita as estruturas anatômicas das folhas de três espécies de Stylosanthes SW.: S.capitata Vogel, S. macrocephala M. B. Ferreira & S. Costa, S. guianensis var. vulgaris M.B. Ferreira & Sousa Costa cv. 'Mineirão' e S. guianensis (Aubl.) Sw. As plantas selecionadas são utilizadas na dieta do gado e potenciais formadoras do fitobezoar. Os fitobezoares foram fragmentados para análise de sua composição e analisados seguindo-se as técnicas da anatomia vegetal. As fibras e cristais encontrados em fitobezoares são similares aos observados nos feixes esclerenquimáticos presentes nos folíolos das espécies de Stylosanthes avaliadas. Nossos resultados apontam diferenças na abundância de fibras nos folíolos de cada espécie. S. macrocephala é a variedade que sugere maior potencial para formação de fitobezoares no trato digestivo de animais que se alimentam dessa leguminosa, devido a abundância de fibras e cristais presentes na folha. Os feixes esclerenquimáticos, idioblastos e a abundância de cristais de oxalato de cálcio nas espécies Stylosanthes podem potencializar a formação de fitobezoares em ruminantes, em especial quando essas leguminosas são consumidas em excesso.

Phytobezoars are structures formed by the aggregation of primarily plant fibers in the digestive tract of ruminants, causing intestinal obstruction that can lead to the death of an animal. Information about the formation of these clusters is scarce. This study identified the main components of bovine phytobezoars and described the leaf anatomy of three species and one variety of Stylosanthes SW.: S.capitata Vogel, S. macrocephala B. Ferreira & S. Costa, S. guianensis var. vulgaris M.B. & Sousa Ferreira Costa cv. 'Mineirão' and S. guianensis (Aubl.) Sw. These plants are used as feed for livestock and probably contribute to the formation of phytobezoars. The phytobezoars were fragmented for analysis of their internal composition and were studied according to plant anatomy techniques. The fibers and crystals found in phytobezoars were similar to the sclerenchyma fiber bundles found in Stylosanthes. The comparative analysis of Stylosanthes showed differences in the abundance of fibers in the leaflets of each species. S. macrocephala is the variety that may have the highest potential for formation of phytobezoars in the digestive tract of animals because there was an abundance of fibers and crystals present in the leaf. The sclerenchyma bundles, idioblasts, and the abundance of calcium oxalate crystals in Stylosanthes species may potentiate the formation of phytobezoars in ruminants, particularly when these legumes are consumed in excess.