Rhizoids

Rhizoids are slender, root-like structures found in various non-vascular organisms, including some plants, algae, and fungi. They anchor the organism to a substrate and assist in the uptake of water and minerals from the surrounding environment. Unlike true roots, rhizoids usually lack vascular tissue and do not function in long-distance transport.

In bryophytes—mosses, liverworts, and hornworts—rhizoids are typically single-celled tubes or short multicellular filaments that extend from the base of the gametophyte or from a protonema. They grow into soil, leaf litter, or other substrates, providing anchorage and facilitating localized absorption of water and nutrients. Because bryophytes lack true vascular tissue, rhizoids play a key role in water uptake at the substrate interface rather than transporting water internally.

In many algae, rhizoids are simple, filamentous structures that anchor the thallus to rocks, substrata, or other surfaces in aquatic environments. They may also help absorb dissolved nutrients from the surrounding water.

In fungi, rhizoids are hyphae that penetrate the substrate, secreting enzymes to break down organic matter and absorb nutrients. They can function in anchorage and digestion, and in some species form networks that support the growth of larger structures.

Rhizoids differ from roots by lacking vascular tissue and, typically, by limited capacity for internal transport. In the evolution of land plants, rhizoids preceded true roots, appearing in the first lineages of non-vascular plants and in some algae as an adaptation to terrestrial or anchored life.