Anatomia e ultra-estrutura do pulvino primário de Pterodon pubescens Benth. (Fabaceae - Faboideae)

Abstract

-(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 ...

Morfoanatomia dos órgãos vegetativos de Smilax polyantha Griseb. (Smilacaceae)

“…De fato, em S. polyantha verifica-se nessa região a ausência de lignificação das células ao redor dos feixes vasculares e espessamento parietal por substâncias pécticas mais pronunciado, que são indicativos da movimentação peciolar (Machado & Rodrigues 2004). Caponetti & Quimby (1956) e Ervin & Evert (1967, sugerem que o ramo caulinar aéreo das espécies de Smilax por eles estudadas possui a porção mais externa do cilindro vascular na forma de um anel esclerificado e, na porção interna, os feixes possuem uma bainha Caponetti & Quimby (1956), Oliveira et al (1973) descrevem o sistema subterrâneo do gênero Smilax como rizoma, e ainda podemos encontrar na literatura a denominação de xilopódio (Almeida et al 1998).…”

Occurrence and evolutionary inferences about Kranz anatomy in Cyperaceae (Poales)

“…To illustrate the ultrastructural features of the four Kranz types, samples from the mid-region of at least three fully expanded leaf blades or scapes were fixed in 2.5% glutaraldehyde solution in 0.1 M phosphate buffer, pH 7.3, for 24 h at 5ºC, post-fixed with 1% osmium tetroxide in the same buffer for 1 h at 25ºC, dehydrated with an acetone series and embedded in Araldite resin (Machado and Rodrigues 2004). Ultrathin transverse sections were obtained using a Diatome diamond knife, and the sections were subsequently stained with uranyl acetate and lead citrate (Reynolds 1963).…”

Plants on the move: Towards common mechanisms governing mechanically-induced plant movements

“…These movements, known as nyctinasty-the stimulus being the presence or absence of light-are present in many legumes including Mimosa, Albizzia, Samanea, Pterodon, Robinia and Phaseolus, and are regulated by the circadian clock. [8][9][10][11] Studies concerning nyctinastic movements in Leguminosae, specially in Mimosa has been undertaken since the 1950s and these were already covered by other reviews in references 9, 12 and 13. However, Mimosa species such as M. pudica Linn., for example, in addition to light induction, also responds to touch stimulus by folding up its leaflets (Fig.…”

“…Anatomical and ultrastructural analysis has been undertaken in a number of Leguminosae species, showing changes in the vacuole size and shape during the movements. 8,10,11,15 The pulvinus motor cells usually have two distinct vacuole types. One is called the tannin vacuole, as it contains great amounts of tannins.…”

“…22 The aqueous vacuole is responsible for most of the changes in the motor cell volume during nastic movements. 8,10,11,15,22 When the pulvinus is open, i.e., when the leaflets are unfolded, the aqueous vacuole of the extensor cell is large, occupying almost all the cell volume and restricting the remaining cytoplasm and nucleus to the cell periphery. 8,10,11,15 The flexor zone cells are generally multivacuolated with sinuous walls.…”