Water lettuce, water cabbage, nile cabbage or Pistia stratiotes is a perennial monocotyledonous plant and the only species in the genus belongs to the family of Araceae. It is originated from Florida and Texas and now widespread in ponds of the warmer parts of the world. It is an aquatic perennial widespread or usually known as aggressive colonizer in the tropics and a noxious weed in some areas as it grows in a very wide variety of aquatic habitats. In some areas, it is called as shell flower that is about 15 centimeter wide, gloating rosettes of ribbed, wedge-shaped leaves resemble blue-green lettuce heads.
The base of the soft leaves is spongy covered in water-repelling hairs, which keeps them buoyant. The fine roots emerging from the base of the rosette extract nutrients directly from the water. It multiplies rapidly and doubles its biomass just over 5 days, triples in 10 days, and quadruples in 20 days. With such quick propagation ability, it is able to disrupt the aquatic flora and fauna underneath, which directly affect the water ecosystem.
It can be self-propagated by separating the stolons, which the rosette can survive independently. The arum-like inflorescence is enclosed in a leaf-like spathe that makes it inconspicuous. It does produce seeds that can withstand freezing and drought, which can be used to propagate as well. The seeds float on the surface for several days, which can be transported by currents and water flow. They are able to germinate on the hydro-soil and float to the surface within 5 days. Substrate such as mud that has low oxygen or high carbon dioxide levels eventually prevent the seeds from germination.
It often grows by people in aquarium or pond act as an insulator against solar radiation to shade the surface and keep the water cool apart from feeding its roots to the fish. In some countries, it may be considered as invasive weed that can quickly clog streams. It has phytoremediation activities that provides attractive foliage that inhibits growth of algae and help keep water clear. However, it affects the water ecosystem and covering dams and waterways, hinders hydro-electric flow, interfering fishing, swimming, boating, water sports, rice crops, and navigation.
The growth of water lettuce can be an alarm to several issues apart from imbalance ecosystem. It is a great breeding site for mosquitoes. Biological control can be used to reduce the population. It is found that it can be attacked by a moth (Spodoptera pectinicornis) in some parts of Asia and USA. Other pests like brown-grey weevil (Neohydronomus affinis Hustache), pyralid moth (Nymphula tenebralis), Hustache (Argentinorhynchus burchi), A. breyeri Brethes, and Hampson moth (Spodoptera pectinicornis).
Water lettuce is an important medicinal aquatic plant that contains alkaloids, glycosides, and steroids, protein, essential amino acids, and minerals. The leaves are rich in vitamin A, B, and C. It has diuretic, antidiabetic, antidermatophytic, antifungal, and antimicrobial properties. Traditionally, it is used to treat ringworm, syphilis, skin infections, eczema, leprosy, ulcers, piles, boils, wounds, fever, tuberculosis, and dysentery in many countries.
Further readings:
Jha, M., Sharma, V., & Ganesh, N. (2012). Antioxidant and wound healing potential of Pistia stratiotes L. Asian Pacific Journal of Tropical Disease, 2, S579-S584.
Khan, M. A., Marwat, K. B., Gul, B., Wahid, F., Khan, H., & Hashim, S. (2014). Pistia stratiotes L.(Araceae): Phytochemistry, use in medicines, phytoremediation, biogas and management options. Pakistan Journal of Botany, 46(3), 851-860.
Lemon, G. D., & Posluszny, U. (2000). Shoot development and evolution in Pistia stratiotes (Araceae). International Journal of Plant Sciences, 161(5), 721-732.
Liu, H. W., He, L. Y., Gao, J. M., Ma, Y. B., Zhang, X. M., Peng, H., & Chen, J. J. (2008). Chemical constituents from the aquatic weed Pistia stratiotes. Chemistry of Natural Compounds, 44(2), 236-238.
Lu, Q., He, Z. L., Graetz, D. A., Stoffella, P. J., & Yang, X. (2011). Uptake and distribution of metals by water lettuce (Pistia stratiotes L.). Environmental Science and Pollution Research, 18, 978-986.
Nahar, K., & Hoque, S. (2021). Phytoremediation to improve eutrophic ecosystem by the floating aquatic macrophyte, water lettuce (Pistia stratiotes L.) at lab scale. The Egyptian Journal of Aquatic Research, 47(2), 231-237.
Tripathi, P., Kumar, R., Sharma, A. K., Mishra, A., & Gupta, R. (2010). Pistia stratiotes (Jalkumbhi). Pharmacognosy Reviews, 4(8), 153.
