Plants use their roots to take in water and minerals. If you have ever pulled a plant from the ground, you may not have noticed that its roots are made of many parts. In this lesson we will examine a critical part of roots known as rhizoids.
Definition of Rhizoids
Rhizoids are simple, hair-like projections that grow out of the epidermal cells of bryophytes.
The term bryophyte refers to a group of plants that includes mosses, liverworts, and hornworts. All of these are nonvascular plants, or plants that don’t have complex tissues for transporting water and nutrients.Rhizoids are similar in structure to the root hairs found on more complex vascular plants. Rhizoids are formed from single cells, unlike roots, which are multicellular organs.
This hornwort is an example of a bryophyte that uses rhizoids to absorb nutrients and water.Rhizoids absorb water from the soil using capillary action.
Capillary action is the ability of a liquid to flow in narrow spaces without the assistance of external forces such as gravity. To imagine how a rhizoid works, think of a tiny coffee stirrer or straw. If you place one in water, you will see the water slowly move upward inside of it. This is how a rhizoid works.
Any amount of water that the rhizoid encounters in the soil is able to slide through the rhizoid and serve as nourishment for the plant.
This magnified image shows the tiny hair-like rhizoids protruding from this plant.
Biologists think all plants originally had to live in water so they could directly absorb water and survive.
The first plants to live on land were the bryophytes. Bryophytes are a group of nonvascular plants that includes mosses, liverworts, and hornworts.Rhizoids are the tiny structures that stick out from the roots of bryophytes.
Rhizoids absorb water and nutrients from the soil through the process of capillary action. Capillary action allows the water to move through rhizoids. Rhizoids are attached to roots and allow plants to absorb water from the soil rather than living in water.