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Em planicies de inundacao, especies de macrofitas respondem a sazonalidade hidrica por meio de alteracao morfologica. Orgaos vegetativos de Ludwigia helminthorrhiza (Myrtales, Onagraceae) podem desenvolver-se em ambiente aquatico e em solo livre de inundacao. Acreditamos que orgaos vegetativos de plantas do segundo ambiente nao apresentem adaptacoes tipicas (e.g., aerenquima, reducao de lignificacao, desenvolvimento de raizes adventicias) de ambientes aquaticos. Mediu-se o comprimento, largura e espessura do limbo; espessura do caule; comprimento dos entrenos; e comprimento das raizes de individuos dos dois ambientes. Analisou-se a anatomia das porcoes medianas dos orgaos e quantificou-se os estomatos. Orgaos vegetativos foram maiores nas plantas desenvolvidas na agua; densidade de estomatos semelhante nas faces do limbo nos dois ambientes, entretanto maior no solo seco. Tecidos de adaptacao a anoxia, como aerenquima, expresso em maior quantidade nas plantas d’agua, facilitando o transporte de gases, reduzindo fitotoxinas e suportando a planta. Ha anatomia similar nos individuos dos dois ambientes, contudo ausencia ou reducao do aerenquima nos orgaos aereos das plantas de solo seco, com presenca apenas de raiz adventicia “principal” e laterais piliferas. Nas plantas d’agua observou-se quatro tipos de raizes adventicias (pneumatoforos e raiz com acrescimo de aerenquima). Evidenciamos plasticidade morfologica, importante para o sucesso no estabelecimento e sobrevivencia da especie no Pantanal. MORPHOLOGICAL RESPONSES OF Ludwigia helminthorrhiza (MART.) H.HARA (ONAGRACEAE) TO PANTANAL WATER SEASONALITY. In floodplains, species of macrophytes respond to water seasonality through morphological alteration. Vegetative organs of Ludwigia helminthorrhiza (Myrtales, Onagraceae) can develop in aquatic environment and in soil free of flood. We believe that vegetative organs of plants of the second environment do not present typical adaptations (e.g. aerenchyma, lignification reduction, adventitious root development) of aquatic environments. The limb length, width and thickness; stem thickness; length of internodes; and roots length of individuals in the two environments were measured. The anatomy of the medial portions of the organs was analyzed and the stomata quantified. Vegetative organs were larger in plants developed in water; density of stomata similar to the limb faces in both environments, but higher in the dry soil. Adapting tissues to anoxia, as aerenchyma, expressed in greater quantity in water plants, facilitating the gases transport, reducing phytotoxins and giving plant support. There is similar anatomy in the individuals of both environments, however absence or reduction of aerenchyma in the aerial organs of dry soil plants, with presence of only “principal” adventitious root and lateral piliferous. In the water plants four types of adventitious roots (pneumatophores and root with addition of aerenchyma) were observed. We demonstrate morphological plasticity, important for success in establishing and surviving the species in the Pantanal. |
