4 research outputs found
Anatomia e ultra-estrutura foliar de Cyperus maritimus Poir. (Cyperaceae): estratégias adaptativas ao ambiente de dunas litorâneas Leaf anatomy and ultrastructure of Cyperus maritimus Poir. (Cyperaceae): adaptive strategies for coastal dune environment
Foram analisados aspectos anatĂ´micos e ultra-estruturais foliares de Cyperus maritimus Poir. visando identificar caracteres adaptativos ao ambiente de dunas litorâneas. Para isto, indivĂduos ocorrentes nas dunas da Praia de Pipa, Rio Grande do Norte, Brasil, tiveram as folhas submetidas a diferentes análises: microscopia de luz, eletrĂ´nica de varredura e de transmissĂŁo. Em vista frontal, a epiderme possui tricomas unicelulares, corpos de sĂlica, cutĂcula estriada e depĂłsitos de cera. Em secção transversal, a epiderme Ă© unisseriada com parede periclinal externa espessa. Os estĂ´matos sĂŁo paracĂticos, podendo o ostĂolo estar obstruĂdo por cera. Abaixo da face adaxial observa-se o parĂŞnquima aqĂĽĂfero. Os feixes vasculares ocorrem em mĂşltiplas fileiras, sendo as perifĂ©ricas compostas por feixes de diâmetro menor que os feixes da fileira central. Foram observados caracteres relacionados Ă sĂndrome Kranz do tipo clorociperĂłide. Aspectos ultra-estruturais, como cloroplastos presentes na bainha do feixe, esses sem grana evidentes, entre outras caracterĂsticas, reforçam a possĂvel ocorrĂŞncia da via C4 nesta espĂ©cie. É a primeira citação para o gĂŞnero Cyperus de cloroplasto nas celulas do tecido vascular. Neste trabalho foi possĂvel observar vários caracteres importantes para plantas submetidas a estresse hĂdrico e salino, como: cera, cĂ©lulas epidĂ©rmicas com parede periclinal externa espessada, parĂŞnquima aqĂĽĂfero e sĂndrome Kranz.<br>Anatomical and ultrastructural aspects of Cyperus maritimus Poir. were analyzed with the aim of identifying adaptive features for the dune environment. Collections were made at Pipa beach, Rio Grande do Norte, Brazil. Leaves were submitted to different analyses: light microscopy, scanning and transmission electron microscopy. In frontal view, the epidermis has unicellular trichomes, silica bodies, a striate cuticle and wax deposits. In transverse section, the epidermis is uniseriate with thickened outer periclinal walls. The stomata are paracitic and the pore sometimes obstructed by wax. Under the adaxial epidermis, there are several layers of aqueous parenchyma. The vascular bundles occur in multiple rows, the peripheral row having bundles with narrower diameters than the central row. Characters related to Kranz syndrome of the chlorocyperoid type were observed. Ultrastructural features support a possible C4 pathway in this species. This work is the first citation of chloroplasts in the cells of the vascular system for the genus. In this study, it was possible to observe several important features of plants submitted to water and salt stress, such as: wax, thickened outer periclinal walls of the epidermal cells, aqueous parenchyma and Kranz syndrome
Pseudodiplostemony, and its implications for the evolution of the androecium in the Caryophyllaceae
A systematic survey of floral nectaries
The construction of classifications, as well as the understanding of biological diversity, depends upon a careful comparison of attributes of the organisms studied (Stuessy, 1990). It is widely known that data from diverse sources showing differences from taxon to taxon are of systematic significance. Dur-ing the 20th century, systematists have emphasized that their discipline involves a synthesis of all knowledge (Stevens, 1994) or, in other words, the variation of as many relevant characters as possible should be incorporated into the natural system to be constructed. The extent to which particular characters are constant or labile will determine their usefulness to syste-matics. In general, more conservative characters will be valuable in defining families and orders, whereas more labile characters may be useful at the ge-neric and specific levels (Webb, 1984). There is no doubt that floral characters are among the most used in the classification of flowering plants. At the same time, they constitute essential features in diagnostic keys to taxa in both taxonomic treatments and Floras (Cronquist, 1981, 1988).Fil: Bernardello, Gabriel Luis Mario. Consejo Nacional de Investigaciones CientĂficas y TĂ©cnicas. Centro CientĂfico TecnolĂłgico Conicet - CĂłrdoba. Instituto Multidisciplinario de BiologĂa Vegetal. Universidad Nacional de CĂłrdoba. Facultad de Ciencias Exactas FĂsicas y Naturales. Instituto Multidisciplinario de BiologĂa Vegetal; Argentin