Leaf morphology and anatomy of Asteraceae of the Pampas biome (sand-fields)

Species of Asteraceae occur predominantly in tropical regions, mainly in grassland areas, such as the sand-fields, which is one of the phytophysiognomies of the Pampas biome and where Asteraceae is the most species-rich family. In these areas the environmental conditions are considered extreme and limiting (sandy soils, high temperatures and luminosity, strong winds and water deficit) for the development of many plants. Therefore, this study aimed to describe the morphoanatomy of the Asteraceae species of the sand-fields and to identify adaptive characteristics that allow their survival in this adverse site. For this, morphological and anatomical analyses in frontal and transverse views were performed on the leaves of 34 species of Asteraceae belonging to different tribes. In addition to characters phylogenetically important in the family, the foliar morphology and anatomy of the species studied show the predominant occurrence of characteristics adaptive to xeric environments, such as reduced and coriaceous leaves, tomentose indumentum, thickened cuticle and epidermal cells, epicuticular wax, amphistomatic leaves and investiment in photosynthetic and support tissues. Although they occupy the same habitat and are under the influence of the same environmental conditions, each species develops a distinct adaptive strategy to survive and, therefore, their resistance or tolerance is the result of the interaction of several factors throughout the life history of the plant.