On Seedling Morphoanatomy of Asteraceae Campestral Species: Some Adaptative and Taxonomic Considerations

Theoretical Framework: The vegetation of Parana State fields is composed mainly of woody grassy savanna, and one of the largest families in specific richness is Asteraceae. The campestral Asteraceae occurs in three microhabitats as dry fields (steppes “stricto sensu”), rocky outcrops (rupestrian vegetation refuges) and humid fields (higrophyllous steppes). Morphology and structure of Asteraceae seedlings can be useful for species recognition in the field at the juvenile stage, and to understand how seedlings establish themselves in different microhabitats. Objective: The aim of this paper was to analyze the seedling structure of 17 Asteraceae species, and to summarize some considerations on anatomical characters of the seedlings, which may be variations environmentally induced and they have some taxonomic or evolutionary value. Method: Cipselae of 17 species of Asteraceae were collected in the state parks of Paraná, Brazil, and placed to germinate in Petri plates. The seedling development occurred in greenhouse. Root, hypocotyl, cotyledons, epicotyl and eophylls were sectioned in rotation microtome, and analyzed in light microscope. Cotyledons and eophylls were investigated in a scanning electronic microscope. Results: Roots are diarch or tetrarch. Hypocotyl may have the root structure and partially or wholly as transition root-stem structure. Epicotyl shows the stem structure. Cotyledons and eophylls are dorsiventral. Trichome density and amphistomaty are xeromorphic characters that occur in the cotyledons and eophylls of the species. Conclusion: Some structural characters have diagnostic value for separation of investigated species, such as hypocotyl structure, root/stem transition type, epidermis, mesophyll tissues and midrib saliency of the cotyledons and eophylls, and presence of secretory ducts.