Aquatic plants, also known as hydrophytes, are plants that live in water, whether in saltwater or freshwater. They thrive in environments like lakes, rivers, and wetlands. Aquatic plants provide shelter for animals such as fish, amphibians, and aquatic insects. They support benthic invertebrates, produce oxygen through photosynthesis, and serve as food for some herbivores. Common examples include waterlilies, lotuses, duckweeds, mosquito ferns, floating hearts, water milfoils, mare’s tails, water lettuces, water hyacinths, and algae.
Aquatic plants have special features that help them survive in water and float on the surface. One main adaptation is lightweight internal cells called aerenchyma. Many have floating leaves or finely divided leaves. These plants can only grow in water or soil that is often wet, making them common in swamps and marshes.
Aquatic plants can live in either freshwater or saltwater. Vascular aquatic plants have evolved multiple times in different plant families. They can be ferns or flowering plants, known as angiosperms, which include both monocots and dicots. The only angiosperms that can grow entirely submerged in seawater are seagrasses, like those in the genera Thalassia and Zostera. Fossils show that some of the earliest angiosperms were aquatic, supporting a watery origin for these plants. Aquatic plants are found widely among angiosperms, with at least 50 separate origins, but they make up less than 2% of all angiosperm species. One of the oldest complete angiosperm fossils, called Archaefructus, is about 125 million years old. These plants need adaptations to live underwater or to float on the surface.
