Estruturas secretoras florais e coleteres foliares em especies de cerrado de Aspidosperma Mart. e Blepharodon Decne. (Apocynaceae s.l.)

AUTOR(ES)
DATA DE PUBLICAÇÃO

2005

RESUMO

The current consensus amongst scientists is that the Apocynaceae s.l. is subdivided into five subfamilies. This paper presents a study of two Aspidosperma species and one Blepharodon species. The Aspidosperma and the Blepharodon belong to the most basal and the most derivative subfamilies respectively. An anatomical study of the species was carried out in order to look into the characterization and occurrence of colleters in vegetative and floral organs. Also, the same study was made in relation to the floral structure, focusing on the secretory structures. The absence of colleters in vegetative organs and flowers of the A. australe Müll. Arg. and the A. tomentosum Mart. proved that this structure is not universal in the family. Foliar and floral colleters were found in the B. bicuspidatum Fourn. They are polymorphic and they vary in number. The described colleters are new in the family. The foliar colleters occupy an interpetiolar position, and they have distinct origins and asynchronous developments. Also, they are deciduous and the secretory phase varies seasonally. The floral colleters alternate with the sepals. They are formed at the beginning of the floral development. They are persistent and they secrete until the flower is in postanthesis. The secretion of the colleters is heterogeneous and it is produced in a single phase. In the foliar colleters, it is made up of the mucilage and the phenolic compounds. But in the calycine, it is composed of the mucilage, fatty acids and phenolic compounds. Besides protecting the vegetative and floral meristems from desiccation, the colleters also protect against phytophagous insects in vegetative branches and against fungi in flowers. Only two secretory structures were found in the A. australe flower: the stylehead epidermis and the laticifers, besides the corolline trichomes with an intermediate structure between glands and tector trichomes, and possibly an obturator from the placenta. The style-head is one of the simplest structures in the family, and the laticifers are unbranched articulated. Although the flowers have an scent, the osmophores were not found, nor was the nectariferous tissue. In the B. bicuspidatum, there are six glands in the flowers: the anther wing epidermis, the style-head epidermis, the stigmatic chamber epidermis, the staminal corona epidermis, the colleters, and the unbranched articulated laticifers. Except for the anther wing epidermis, the other structures continue secreting until the floral anthesis. The floral structure of the A. australe and the B. bicuspidatum is very distinct, but some secretory structures that are universal (in the family) show the relationship between the two species, such as the style-head epidermis and the same type of laticifer. The restricted variety of floral secretory structures of the A. autrale confirm the basal position of the genera in the subfamily and in the tribe, a wide variety of floral glands of the B. bicuspidatum and its complex floral structure confirm its derivative position in the family and subfamily

ASSUNTO(S)

aspidosperma apocynaceas histoquimica coleteres blepharodon anatomia vegetal glandulas florais

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