You may be familiar with green moss growing on a rock. Moss is a bryophyte, a type of nonvascular plant found near fresh water. This lesson describes bryophytes, including mosses, liverworts, and hornworts.
What Are Bryophytes?
Have you ever fallen on a slippery rock while fishing or exploring a stream? If so, you’ve been a victim of a bryophyte! Don’t worry, they are not something to be feared.
Bryophytes are small, non-vascular land plants that require water for reproduction. Land plants fall into two categories: those that have special tissues to transport water and other materials, called vascular plants; and those that do not have specialized tissues, called non-vascular plants. Bryophytes are non-vascular, so they do not have the right types of tissues to develop roots, stems, or leaves.There are three main types of bryophytes: mosses, liverworts, and hornworts.
Some scientists now only consider mosses to be bryophytes, but we’ll discuss all three in this lesson. Now let’s explore their defining characteristics and specialized reproductive cycle, as well as look more closely at some example bryophytes.
Bryophytes typically measure one to two centimeters tall. They lack tissues to provide structure and support that other land plants have, so they cannot grow taller.
Instead, bryophytes grow close together into a cushion-like covering over soil, rocks, tree trunks, and leaves.Though they require water for hydration as well as reproduction, they are able to survive on land because of special adaptations. Bryophytes are covered in a waxy cuticle that helps them to retain water. As water flows through an area, it is absorbed by bryophytes. Bryophytes hold on to water like a sponge, helping creatures who depend on water for survival as well as reducing flooding in an area.
In the bryophyte life cycle, water is necessary for reproduction. The life cycle has two distinct parts.
In the diploid stage, sperm and eggs, produced by the gametophyte, are able to join as sperm moves through water, using a special tail-like structure. Diploid means that the chromosomes are paired: one from the egg, one from the sperm. The sperm move through the water down into the part of the plant that holds the egg.Once the egg is fertilized, the haploid stage begins in the sporophyte that forms. Haploid means that the chromosomes are unpaired and formed during meiosis during asexual reproduction. Spores are made and released from the sporophyte capsule.
The spores land in a moist area and grow into new plants. A system of stringy filaments, called protonema, develops and spreads out, and a single spore can very quickly take up a large area.Liverworts and hornworts are similar to mosses in that they all require water to reproduce and send spores out to grow into new plants, but the reproductive structures within and how they spread their spores are slightly different.
Hornworts, liverworts, and mosses are all examples of bryophytes. These plants are an important structural component of many damp habitats. For example, moss grows into a dense covering like a mat.
Special root-like structures called rhizoids help anchor the moss to the surface it grows on. The layers of decomposing moss can form an island that acts as a foundation for other plants, shrubs, and trees to grow.If you are looking for a bryophyte, head to a damp environment like a bog. Mosses look like many tiny plants growing close together in a spongy mat or cushion. Some liverworts have bodies that are divided into lobes. Some say that a liverwort looks like an actual liver in our bodies (it has lobes), and that is how it got its name! Hornworts can be greenish-blue in color and are found in tropical areas as well as streams.
To find a bryophyte, such as mosses, liverworts, or hornworts, look for short, spongy plants growing along the rocks, soil, and trees in a damp freshwater environment.Bryophytes are closely tied to water; they need it to reproduce and survive, and they also hold water. They are covered in a waxy cuticle which helps the ecosystem they thrive in.Bryophytes are non-vascular plants, which means they do not have specialized tissues to move water and materials within the plant. If you looked closely, you would see that they do not have roots, stems, or leaves. However, they do have rhizoids, which are root-like structures.
Definitions to Remember
- Bryophytes: plants that need water to reproduce and grow, mainly mosses, liverworts and hornworts
- Non-vascular: plants without the tissue necessary to grow roots, stems or leaves
- Gametophyte: reproductive phase during which sperm moves through the water down to where the plants eggs are
- Sporophyte: spores are created and released
- Protonema: stringy filaments grow and spread
- Rhizoids: root-like structures
As you complete the lesson on bryophytes, make certain that you can easily:
- Provide a description of bryophytes
- Remember the three main types of bryophytes
- Discuss the characteristics of these plants
- Highlight the two parts of the bryophyte life cycle