Biological flora of Central Europe: Marsilea quadrifolia L.
Marsilea quadrifolia L. is a leptosporangiate aquatic fern which has a played key role in the evolutionary history of plants. It is characterized by heterospory, the ancestral progressive trait that led to the evolution of seeds. The species has creeping, fleshy, adventitious roots containing multiple rhizomes. From the rhizomes a four-leaf clover grows above the water level with a long petiole, at the base of which the sporocarps containing spores are located. Its life cycle is characterized by alternation of generations; reproduction occurs either sexually or by vegetative propagation. The species grows in wet habitats containing shallow water. In the natural environment this includes lakes and small rivers; in agricultural areas it can be found in ditches and rice fields. The species can tolerate nutrient rich waters and because of its phytoremediation properties is capable of partially counteracting the negative effects induced by a moderate organic enrichment of sediments. It has been harvested for centuries in Asian countries as both a food source and for ethnobotanical use in Ayurvedic medicine. Supposed medicinal properties include antibacterial, diuretic, depurative, cytotoxic and antioxidant effects, but these require further investigation and testing.M. quadrifolia has a widespread distribution, occurring throughout central-southern Europe and extending from Eurasia to tropical and temperate areas of eastern Asia and North America, where it is considered a non-native species. Despite its wide distribution, in its home range the species is threatened with extinction and has already been locally extirpated in several European countries. As a result, it is listed as "Vulnerable" in the European Union Red List due to its scattered distribution and declining population. Habitat loss and degradation, excessive water eutrophication, and agricultural practices such as the use of herbicides, mechanization and simplified rotation are the main threats to the species. As it is listed in Appendix I of the Bern Convention and in Annexes II and IV of Directive 92/43/EEC as a strictly protected species, in situ and ex situ conservation activities have been conducted in most European countries. Reintroduction, cultivation in botanical gardens and in vitro propagation are the most commonly applied conservation methods.