Mixotrophy in aquatic plants, an overlooked ability.

Aquatic Embryophytes play a key role in the proper functioning of aquatic ecosystems, where carbon (inorganic and organic forms) is pivotal in biogeochemical processes. There is growing awareness that mixotrophy, the direct use of exogenous organic carbon by autotrophs, is a widespread phenomenon and that it has emerged recurrently in the evolution of many autotrophic lineages. Despite living in an environment providing organic matter and presenting many favourable predispositions, aquatic plants from the Embryophytes, except carnivorous ones, have never been deeply investigated for mixotrophy. Here, we address the possibility that aquatic plants may exhibit mixotrophy, a prospect overlooked by research until now, and that this may be much more widespread than imagined under the conventional paradigm of plants considered as strict autotrophs. Aquatic plants are crucial for the proper functioning of aquatic environments. So far, mixotrophy, widespread in aquatic microbial communities and in certain terrestrial plants, has been studied rarely in aquatic plants other than carnivorous ones. New evidence, particularly in Lemna and other close genera, suggests that mixotrophy is much more widespread than previously thought. Three processes could be involved, namely biotrophic associations, capture of prey (e.g., in carnivorous plants), and absorbotrophy (uptake of dissolved organic carbon). The latter process seems to be the most probable hypothesis in regard to the physiology of aquatic plants, but further research at both organism and cellular levels is needed to understand and clarify the processes involved and their importance. This opinion opens a new window of opportunity in aquatic ecology, with possible unsuspected applications in water management. [ABSTRACT FROM AUTHOR]