Trade-off in leaf and root investment of an abundant aquatic macrophyte in a Neotropical floodplain

Phenotypic plasticity in macrophytes is observed when morphological and physiological features respond to environmental variation, and a trade-off is observed when there is investment in a specific feature to the detriment of another. We investigated causes for the trade-off in leaf and root investment in Eichhornia azurea, a macrophyte of major importance in structuring ecosystems in a large Neotropical floodplain. At riverine systems, the leaf/root ratio of E. azurea is typically related to different environmental conditions. We hypothesized that the trade-off between leaf and root investment would depend on water flow and water renewal. Our results indicated that, in lentic ecosystems, the investment in roots was higher than in leaves when compared to semi-lotic ecosystems. This result was probably explained due to the poor nutrient availability as a consequence of low water flow in lentic ecosystems. In semi-lotic ecosystems, instead, nutrient absorption may be higher, favoring high leaf investment. Indeed, when this trade-off is compared between lentic habitats with different water exchanges, investment in leaves is higher in habitats with higher water exchange, and consequently with a constant renewal in nutrient availability.