Morphological variation in Eichhornia azurea (Kunth) and Eichhornia crassipes (Mart.) Solms in relation to aquatic vegetation type and the environment in the floodplain of the Rio Parana, Brazil

Eichhornia azurea and E. crassipes are the most frequent dominants of aquatic vegetation in the floodplain of the Upper Rio Parana in Brazil. Morphological traits of samples collected at sites where they dominated the vegetation were measured and compared between vegetation types identified in the floodplain. Total leaf weight, specific leaf area and the leaf to root weight ratio of E. azurea and total leaf dry weight, total leaf area and total plant dry weight of E. crassipes differed significantly between vegetation types from 1999. Pearson correlation coefficients indicated a number of significant relationships between morphological traits and environmental variables. Five E. azurea traits increased linearly with water depth and four with water clarity. The leaf to root weight ratio also increased linearly with sediment iron and calcium content. E. crassipes total root dry weight and total plant dry weight were respectively quadratically related to sediment calcium and the euphotic proportion of the water column. Total leaf dry weight and total plant dry weight increased linearly with water depth while remainder dry weight decreased linearly with sediment phosphorus content.