Structural variations among monocot emergent and amphibious species from lakes of the semi-arid region of Bahia, Brazil

Temporary lakes are common in the semi-arid region of the State of Bahia and form water mirrors in the rainy season. In this period, various vegetal species appear having different life forms adapted to the seasonality conditions of the rainfall regime. This work surveyed the adaptive anatomical structures of some emergent and amphibious monocot species occurring in these lakes. We studied the anatomy of roots, rhizomes, leaves and scapes of Cyperus odoratus, Oxycaryum cubense, Pycreus macrostachyos (Cyperaceae) - amphibious species; and of Echinodorus grandiflorus (Alismataceae), Eichhornia paniculata (Pontederiaceae) and Habenaria repens (Orchidaceae) - emergent species. The anatomical features of the dermal, fundamental and vascular systems confirming the tendency of the adaptive convergence of these plants to temporary lacustrine the environment include: single layered epidermal cells with a thin cuticle layer in the aerial organs; the presence of air canals in all the organs; few or no supporting tissues; and less numerous conducting elements and thinner cell walls in the xylem. The reduction of the supporting tissues, the number of stomata, which can even be absent, and the number of conducting elements and the degree of cell wall lignification in the xylem of the emergent species is more accentuated than that of the amphibious species. The pattern of distribution of aerenchyma in the roots of the studied species was considered important to distinguish between amphibious and emergent life forms

Developmental anatomy of Cyperus laxus (non-Nranz) and Fimbristylis dichotoma (Kranz) (Cyperaceae, Poales) and tissue continuity

The Cyperaceae species are present in different ecosystems and constitute the herbaceous extract. Of the approximately 5,500 species of the family; a third has Kranz anatomy, representing an important characteristic of the taxonomy and phylogeny of the group. In Cyperus laxus L. (non-Kranz) and Fimbristylis dichotoma Vahl (Kranz), development begins with germination that is marked by the emergence of the coleoptiles, followed by the primary root, which is ephemeral. The rhizome originates from the mesocotyl and it promotes the vascular connection between the roots, leaves and scapes. The continuity of the tissues is evidenced by the presence of an endodermis and pericycle in all vegetative organs. Leaves and scapes differ between the two species by the arrangement of mesophyll cells, which is regular in Cyperus laxus (non-Kranz) and arranged radially in Fimbristylis dichotoma (Kranz). Also differ in the number of bundles sheaths: two in Cyperus laxus (non-Kranz) and three in Fimbristylis dichotoma (Kranz). The outer bundle sheath in both species constitutes the endodermis, and the inner sheath in Cyperus laxus and the middle and inner sheaths in Fimbristylis dichotoma constitute the pericycle.As espécies de Cyperaceae estão presentes em diferentes ecossistemas e constituem o extrato herbáceo. Das aproximadamente 5,500 espécies da família, um terço possui anatomia Kranz, representando uma importante característica da taxonomia e filogenia do grupo. Em Cyperus laxus L. (não Kranz) e Fimbristylis dichotoma Vahl (Kranz), o desenvolvimento começa com a germinação que é marcada pela emergência do coleóptilo, seguido da raiz primária, que é efêmera. O rizoma se origina do mesocótilo e promove a conexão vascular entre raízes, folhas e escapos. A continuidade dos tecidos é evidenciada pela presença de endoderme e periciclo em todos os órgãos vegetativos. Folhas e escapos diferem entre as duas espécies estudadas no arranjo das células do mesofilo, que é regular em Cyperus laxus (não Kranz) e dispostas radialmente em Fimbristylis dichotoma (Kranz). Também diferem no número de bainhas vasculares: duas em Cyperus laxus (não Kranz) e três em Fimbristylis dichotoma (Kranz). A bainha externa em ambas as espécies constitui a endoderme, e a bainha interna em Cyperus laxus e a mediana e a interna em Fimbristylis dichotoma constituem o periciclo