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-(Anatomy and ultrastructure the primary pulvinus of Pterodon pubescens Benth. (Fabaceae -Faboideae)). The anatomy and ultrastructure of Pterodon pubescens primary pulvinus were studied to verify if slow leaf movements are associated with pulvinus cells features. Pulvini samples deriving from leaf with open and closed leaflets were prepared following usual techniques using light and electron microscopy. The pulvinus has a unisseriated epidermis covered by a thick cuticle and many trichomes, cortex with several layers of parenchyma cells (motor cells), a central vascular core surrounded by septate fibers, and a reduced pith. Cortical cells features change with the turgescence degree, showing alteration in the cell size and shape, cell wall thickness, frequency and arrangement of plasmodesmata, vacuole content and number and cytoplasm density. Septate fibers around the phloem were described for the first time in pulvini. The wide occurrence of plasmodesmata, the apoplastic barriers absence and the lignification scarcity (only present in xylem vessels) indicate a continuity, both simplastic and apoplastic, from the epidermis to the vascular tissue of the pulvinus. In Pterodon pubescens, primary pulvinus features are compatible with slow movement pulvini; the features shared to speedy movement pulvini are the presence of vacuoles with phenolic substances in the cortical cells and amiloplasts in the endodermal cells. Movements caused by P. pubescens primary pulvinus are associated with changes in both the apoplastic (wall infoldings) and symplastic (vacuolar reorganization).Key words -anatomy, Fabaceae, Pterodon pubescens, primary pulvinus, ultrastructure RESUMO -(Anatomia e ultra-estrutura do pulvino primário de Pterodon pubescens Benth. (Fabaceae -Faboideae)). A anatomia e ultra-estrutura do pulvino primário de Pterodon pubescens foram estudadas para verificar se os movimentos lentos de suas folhas estão associados às características celulares do pulvino. Amostras de pulvinos provenientes de folhas com folíolos abertos e fechados foram preparadas segundo técnicas usuais em microscopia de luz e eletrônica. O pulvino é constituído por epiderme unisseriada recoberta por cutícula espessa e tricomas tectores, córtex com diversas camadas de células parenquimáticas (ou motoras), feixe vascular central rodeado por bainha de fibras septadas e medula reduzida. As características das células motoras variam de acordo com o grau de turgescência do pulvino, ocorrendo alterações no tamanho e forma das células, na espessura das paredes celulares, na freqüência e organização dos plasmodesmos, no conteúdo e número de vacúolos e na densidade do citoplasma. Fibras septadas ao redor do floema estão sendo descritas pela primeira vez em pulvinos. A ampla ocorrência de plasmodesmos, a ausência de barreiras apoplásticas e a escassez de lignificação (presente unicamente nos vasos do xilema) indicam uma continuidade, simplástica e apoplástica, desde a epiderme até o tecido vascular do pulvino. Em P. pubescens, as características do ...

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This study investigates the histology and subcellular features of secretory cavities during the development of the shoot apex of Metrodorea nigra A. St.-Hil. in order to better understand the functioning of these glands. This Rutaceae species is a very suitable model for studying secretory cavity life span, since the shoot apex exhibits both dormant and growth stages during its annual cycle. Shoot apices were collected during the dormant and growth stages from populations of M. nigra growing under natural conditions. Materials were processed using standard techniques for light and electron microscopy. The secretory cavities originate under the protodermis, and their initiation is restricted to the early developmental stage of shoot organs, which are protected by a hood-shaped structure. Secretory cavities have a multi-seriate epithelium surrounding a lumen that expands schizolysigenously. Oil production begins before lumen formation. When the shoot apex resumes development after the dormant stage, the glands remain active in oil secretion in the developing shoot apex and fully expanded leaves. The mature epithelial cells are flattened and exhibit very thin walls, large oil bodies, leucoplasts surrounded by endoplasmic reticulum, and mitochondria with unusual morphology. The tangential walls of the epithelial cells facing the lumen undergo continuous peeling. The vacuole extrusion appears to be the primary mode of release oil into the lumen, in an exocytotic way. The continuity of oil secretion is ensured by the replacement of the damaged inner epithelial cells by divisions in the parenchyma layer that surround the oil gland, likely a meristematic sheath.

Background and Aims In mature grass leaf blades as seen in cross-section, oblong cell-like structures have been interpreted most recently as intercellular gas spaces delimited by successive collapsed fusoid cells. These cells have been reported in at least seven of 12 subfamilies of Poaceae and are considered a synapomorphy for the family; however, no developmental work has been performed to verify their meristematic origin or to assess possible homologies within the graminid clade (= Flagellariaceae + [(Joinvilleaceae + Ecdeiocoleaceae) + Poaceae]) or among subfamilies of Poaceae. A developmental study was therefore carried out, including 20 species in three families (Flagellariaceae, Joinvilleaceae and Poaceae), representing the earlier-diverging and derived branches within the graminid clade and Poaceae. • Methods Light microscopy was combined with scanning electron microscopy, cryoscanning electron microscopy and transmission electron microscopy to study the development of leaves taken from the shoot apex of young plants. Mature leaf blades also were taken from living or dried plants and the mid-portion was studied. • Key Results Developmental results show that, in mature leaf blades as seen in cross-section, one apparent fusoid cell is typically a cavity resulting from the collapse of the initial fusoid cell and its internal divisions, which are herein interpreted as derivative cells with formation of cell plates only. Each cavity is delimited by successive collapsed fusoid cells arranged perpendicularly to the veins. Fusoid cells in all studied Poaceae members originate from the ground meristem, as do the colourless cells in Joinvillea ascendens (Joinvilleaceae). These two types of mesophyll cell have a strongly similar ontogeny, distinguished mainly by the collapse of the fusoid cells in Poaceae, which is not observed in the colourless cells in J. ascendens. • Conclusions Within the Poaceae, the meristematic origin of fusoid cells is the same in the early-diverging lineages, BOP clade and Panicoideae, and thus they are homologous within the family. The same topography and meristematic origin suggest that fusoid cells in Poaceae and colourless cells in Joinvilleaceae are homologous. The results also suggest that the role played by the fusoid cells in young grass leaves is related to synthesis and storage of starch granules at early stages of development.

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