Marilia de Moraes Castro

Utilização de estruturas secretoras na identificação dos gêneros de Asteraceae de uma vegetação de cerrado

(Utilizacao de estruturas secretoras na identificacao dos generos de Asteraceae de uma vegetacao de cerrado). Com o objetivo de se verificar o possivel valor taxonomico das estruturas secretoras para especies de Asteraceae, foi efetuado um levantamento de tipos destas estruturas em folhas de 72 representantes da referida familia, que compoem parte da vegetacao do cerrado da Reserva Biologica de Moji Guacu (Sao Paulo, Brasil). As folhas foram selecionadas e tratadas segundo as tecnicas usuais empregadas para materiais herborizados; a regiao mediana destas pecas foi cortada a mao livre, enquanto que folhas inteiras foram diafanizadas e coradas. O levantamento evidenciou ductos, idioblastos, hidatodios e l0 diferentes tipos de tricomas secretores. Avaliados conjuntamente, os tipos de estruturas secretoras tem valor diagnostico em nivel generico, o que permitiu a elaboracao de uma chave para identificacao dos generos desta vegetacao de cerrado. Algumas consideracoes foram efetuadas em nivel de tribo, sugerindo-se uma possivel afinidade entre os representantes das tribos Eupatorieae e Heliantheae, e evidenciando-se a homogeneidade observada para os elementos constitutivos da tribo Vernonieae; nestes casos, considerou-se a ausencia ou a presenca dos diferentes tipos de estruturas secretoras e a posicao que ocupam nos orgaos foliares.

Laticíferos articulados anastomosados: novos registros para Apocynaceae

Laticifer presence is universal in Apocynaceae, in the classic literature the type described for this family is the non-articulated. Later researches have proved the occurrence of articulated laticifers only in four species, giving rise to controversies on their origin. The results obtained in our studies differ from those reported for most species of this family. In both Aspidosperma australe Mull. Arg. (Rauvolfioideae) and Blepharodon bicuspidatum Fourn. (Asclepiadoideae), the laticifers are of the articulated anastomosing type because they are formed by adding cells with rapidly dissolving transverse walls. Laticifers originate from ground meristem and/or procambium and form a branched system, they are in secretory phase since the early stages of formation in different organs, releasing latex only when the plant is damaged. The laticifer walls are exclusively pectic-cellulosic and their chemical characteristics probably change during their development. Vegetative organ laticifers occur in all stem and leaf tissues, except epidermis and medullary parenchyma of A. australe. In the flower, laticifers are found in all floral organs, except in the medullary parenchyma of the pedicel of A. australe and in the ovules of both species. The presence of the same type of laticifer in these two genera, which represent the most divergent subfamilies within the Apocynaceae corroborates the current circumscription of this family. The latex has protective function, allowing the species of this family to succeed in different environments.

Ultrastructural observations on the foliar secretory cavities of Porophyllum lanceolatum DC. (Asteraceae)

Summary The ultrastructure of foliar secretory cavities of Porophyllum lanceolatum DC. was studied at three developmental phases, and shows to have the basic characteristics of terpene-secreting glands. The ability to secrete is already present in young, differentiating cavities. In the epithelial cells, dark osmiophilic material occurs in plastids, mitochondria, the nuclear envelope, the endoplasmic reticulum (ER) and dictyosomes, indicating the participation, in some way, of such structures in the secretory process. The ER is seen to be associated with plastids (periplastidal ER), mitochondria and the nuclear envelope, seeming to play a role in transporting the secretory material from these organelles to the plasmalemma. The granulocrine mechanism, involving portions of ER, and independently, vesicles derived from dictyosomes, is considered to be the main process for the elimination of secretory material from the protoplast. Multivesicular, multilamellar and mixed bodies were also observed, as well as microbodies (associated with ER in some cases), in the epithelial cells. In the cells of the gland sheath the walls are thicker than those of the epithelial cells; starch is often present in their plastids

Coléteres foliares e calicinais de Temnadenia violacea (Apocynaceae, Apocynoideae): estrutura e distribuição

(Foliar and calycine colleters of Temnadenia violacea (Apocynaceae, Apocynoideae): structure and distribution). The present work describes the origin, structure and position of the colleters on vegetative and floral apices of Temnadenia violacea (Vell.) Miers and confirms the presence of mucilage in the secretion produced by those structures. The number of foliar colleters ranges from 9 to 11 per primordium and from 18 to 22 per node; only one has an axilar origin, while the others originate along the margins. Concerning position, five of them are petiolar and the others are interpetiolar. There are two types of foliar colleters: standard and sessile, and they consist of a main body composed of a central core of elongated parenchyma cells surrounded by a secretory palisade epidermis and a thin cuticle. Tector trichomes and vascular tissue occur only on the distal marginal colleters. On the floral apices, the calycine colleters are formed at the base of the calyx, three of them opposite the sepals. All of the calycine colleters have a central core of elongated parenchyma cells, a secretory palisade epidermis, a thin cuticle, and are sessile. The calycine colleters are not vascularized and the laticifers are narrow. Mucilage was detected in the secretion of both foliar and calycine colleters.

Leaflet secretory structures of five taxa of the genus Zornia J.F. Gmel. (Leguminosae, Papilionoideae, Dalbergieae) and their systematic significance

A survey of the secretory structures of leaflets has been carried out for five taxa of the genus Zornia J.F. Gmel. to assess possible taxonomic value of the glands, taking into account that these taxa, Zornia curvata Mohlenbr., Z. gemella Willd. ex Vogel, Z. glabra Desv., Z. latifolia Sm. and Z. reticulata Sm., have overlapping diagnostic characters. The leaflet secretory structures of the five studied taxa of Zornia were mucilage epidermis, mucilage cavities, and idioblasts secreting phenolic compounds. Mucilage epidermis is found in all five aforementioned taxa. Mucilage cavities are observed on both epidermal surfaces of the leaflets in four taxa, the exception being Z. glabra, whose cavities occur only on the abaxial surface. Idioblasts secreting phenolic compounds were detected only in the mesophyll of Z. latifolia and Z. reticulata. The joint occurrence of mucilage epidermis with mucilage cavities seems to be of unifying value for the five taxa analyzed. The position of mucilage cavities and the occurrence of secretory idioblasts in the mesophyll of the leaflets are of diagnostic value, providing a key to enable identification of the taxa studied. This study reveals that the secretory structures provide important information in support of systematic studies of the Leguminosae. In relation to the five taxa of Zornia studied, current results suggest recognition of four species: Z. curvata, Z. glabra, Z. latifolia, and Z. reticulata.

Gynostegium Morphology of Mesechiteae Miers (Apocynaceae, Apocynoideae) as It Pertains to the Classification of the Tribe

In order to investigate morphological patterns in Mesechiteae and test the new circumscription of the tribe, the gynostegium structure of nine species belonging to Forsteronia, Mandevilla, and Mesechites, with two species from Secondatia as outgroup, were comparatively studied. Our results support the most recent circumscription of Mesechiteae, including Forsteronia, Mandevilla, and Mesechites and excluding Secondatia. The gynostegia of Forsteronia, Mandevilla, and Mesechites have the same basic organization: a proliferation of parenchyma cells in the style head forms five projecting ribs that are adnate to an expanded portion of the connective below the thecae, here named the “staminal retinacle.” This adnation is very tenuous in Forsteronia (few cells of the staminal retinacle are effectively connected to the style head) but much stronger in Mandevilla and Mesechites (several cells of the staminal retinacle are connected to the style head). The observed differences in the size of the style head ribs and the degree of adnation to the stamens also support the three major clades recognized within the tribe. The gynostegium of Secondatia has a different organization, of the type reported for representatives of the tribe Apocyneae: the style head has no projecting ribs, and its epidermal cells are interdigitated with, but not adnate to, unicellular trichomes of the staminal retinacle.

Hipanto e tubo estaminal em Xylopia aromatica (Lam.) Mart. (Annonaceae)

(Hypanthium and staminal tube in Xylopia aromatica (Lam.) Mart. (Annonaceae)). A woody ring surrounding the carpels was observed in longitudinal sections of flowers of five species of Xylopia L.. The stamens and staminodes were spirally inserted on this ring. An anatomical study of the mature flowers of Xylopia aromatica (Lam.) Mart. was conducted to elucidate the nature of this structure, concentrating on the vascularization from the base of the receptacle to the stamens, staminodes and carpels. The woody ring was shown to be appendicular and of mixed origin. It consists of the fusion of the sepals, as well as external and internal petals and filaments in the basal region, thereby constituting the hypanthium. In the apical portion it is exclusively formed by the fusion of the filaments, thus constituting a staminal tube. The epidermal cells covering the stamens and staminodes have a lignified and thickened wall, distinguishing them from the other epidermal cells of the sepals, petals and carpels. Such cells also cover the woody ring, demonstrating its staminal origin. The woody texture of this ring is probably due to the presence of lignin in the walls of its epidermal cells. According to the literature, this ring has been interpreted as being of receptacular nature, without any anatomical support. The appendicular origin of the hypanthium is here reported for the first time for both of the genus Xylopia and Annonaceae.