Table of Contents
- What is Moss?
- Physical Characteristics of Mosses
- Moss Classification
- Uses and Cultivation of Moss
- Does Moss Have Roots?
- Lesson summary
Moss may be the perfect forest carpet or stylish addition to any homemade fairy house, but did you know that moss is actually a plant and not a lichen? Moss is a type of ancient plant that is very different from what we think of as a plant. It's green like other plants are, and makes its own food through photosynthesis, but moss doesn't have flowers, roots, or even water-transporting tissues like other plants do. Ancient ancestors of moss were some of the first plants to evolve out of a completely aquatic environment. Because of this, moss is nonvascular, meaning it does not have the water and nutrient transportation tissues other land plants have that allow them to live without direct contact with water. Moss still needs that direct contact with water to live. Moss keeps a few drops of water in its conductive stem-like tissue and relies on diffusion of water to transport the nutrients it needs. Moss is often confused with lichens because of its low growth and interesting shapes and textures, but it is in fact very different from other plant-like species. Let's dive in and learn about what makes moss so special in the botanical world.
The scientific definition of moss is classified as any non-vascular plant in the Bryophyta group in the kingdom Plantae. Non-vascular means that moss does not have the tissues other land plants have in order to grow tall and grow away from water, such as phloem and xylem. There are over 12,000 species of moss worldwide, and because it is an ancient plant, it has adapted to a wide variety of environments. The scientific requirements for a plant to technically be a moss, in addition to being non-vascular, include rhizoids instead of roots, flat and often single-celled leaves, and small clumping or sheet-like growth patterns.
As mentioned above, moss is a bryophyte. Bryophytes include mosses, hornworts, liverworts, and lichen, and though they look very different from other land plants, they still make their own food by photosynthesizing. Bryophytes are very small and grow close to the ground. Bryophytes are nonvascular plants, meaning they do not have the tissues required to transport nutrients, reproduce, grow tall, or even stay upright without water. Because of this, bryophytes usually grow low to the ground or surface they are attached to.
Bryophytes do not have flowers, but rather are spore-producing plants that rely on water to reproduce. Bryophytes have two distinct generations, which can be thought of as life cycle phases; the gametophyte (sexual) generation and the sporophyte (nonsexual) generation. In the gametophyte, gametes, or reproductive cells, are produced and released. Sperm travels by way of water to where the egg is produced and stored, and fertilization takes place. Then moss enters the sporophyte generation when the fertilized eggs are released as spores by the sporangium.
Examples of moss can be categorized into different groups depending on how it grows. Pleurocarpous mosses, or sheet mosses, grow in mats, either chaotically or symmetrically. Some sheet mosses are fern-like, and grow slightly upwards, while others are very flat and cover large surface areas. Another type of moss is acrocarpous mosses, or clumping, cushion, or pillow mosses. Acrocarpous mosses look like little trees that grow upright with leaf-like structures growing out on all sides from a central stem. They are usually quite short and grown in a round cluster that looks like, you guessed it, cushions!
Haircap moss, or Polytrichum commune, is a very common species of moss that grows upright and looks like tiny trees. They have dark green base leaves with very vibrant green tops that look like little green fireworks. Haircap moss is taller than other mosses, and has longer rhizoids than other mosses, more closely resembling true roots, and allows the clumps to stay firmly in place.
Rock Cap Moss, or mosses in the Dicranum genus, is another type of moss that grows densely on rocks. Also called fork moss or wind-blown moss, these mosses grow in tight clumps with upward-facing shoots, and rarely grow branches. Rock cap mosses grow in very shady environments and can sometimes get sunburnt by even short exposures to full sunlight.
Mosses are integral parts of the ecosystem. They can transport and provide nutrients to surrounding land plants, and they also can aid in soil erosion by retaining water that would otherwise wash away topsoil. Mosses have several characteristics that botanists look for in identification. All mosses inhabit moist shady environments, though some species have evolved to thrive in dryer sunnier locations, depending on the species.
Rhizoids are root-like structures (see below) that anchor the moss in place. Rhizoids are not roots because they do not absorb water and nutrients inside the structure, but outside. Rhizoids in mosses are also multicellular, which is a characteristic that sets mosses apart from others in the bryophyte group.
Another key characteristic is the stem and flat leaves of moss. Mosses do not have true leaves, in that they are not made up of all the layers a typical land plant leaf has. The leaves of mosses, because they are green, contain chlorophyll and aid in photosynthesis. The leaves are always attached to the stem, and in most species are just one cell thick! This causes the leaf to be flat.
Mosses are also non-flowering plants, and instead, send out spores to reproduce. These spores must have water to travel on and are released from a stalk, or seta, that extends above the stems of the moss. The spores are then released from a capsule, or calyptra, at the top of the seta.
There are eight scientific classes of moss. Takakiopsida, Sphagnopsida, Andreaeopsida, Andreaeobryopsida, Oedipodiopsida, Polytrichopsida, Tetraphidopsida, Bryopsida.
Takakiopsida has two species in it and until recently was thought of as a liverwort. In Asia, its common name is "puzzle moss", which is in reference to its puzzle-like growth pattern.
Sphagnopsida is most known for its species of Sphagnum moss, or bog moss, or peat moss. Sphagnum moss can grow to impressive lengths when in soggy environments like swamps and bogs. It is known for its single stem and starlike leaves that grow in all directions around the stem. Sphagnum can hold up to 20 times its dry weight in water. Sphagnum has many uses. It is a common ingredient in peat, which is a dense and decaying form of plant matter used for gardening and as a fuel source. It has historically been used to dress wounds, due to its high absorption ability, and has also been used in colder climates as housing insulation.
Andreaeopsida mosses are usually short, spiky, and brittle. They are found on rocks in cold environments. Rock cap moss belongs to this class. Mosses in this class also grow their spore capsules at the tips of their branches and not on stalks, which form dark brown or red cushions at the tips of the moss stems.
Andreaeobryum has only one species in it, Andreaeobryum macrosporum, thought to be the missing link between Andreaeopsida and the Bryopsida group. It grows in Alaska and the northern parts of Canada.
Oedipodium griffithianum is the only species in the Oedipodiopsida class. It is a very interesting moss that has rounded leaves.
Members of the class Polytrichopsida tend to be larger than other mosses, with thicker stems and rhizoids. Common Haircap Moss is in this class.
Tetraphidopsida has just three species in it, and they also grow in northern colder environments. The key identifying feature of mosses in this group is the four teeth-like appendages that protrude from the opening of the spore capsule.
Bryopsida is the largest class of moss, containing 95% of all moss species. The key identifying feature of members of this class is the small teeth-like ridges at the opening of each sporophyte capsule. The capsules look quite other-worldly!
Mosses are used in a variety of ways all across the world. Moss is used commercially in gardens and terrariums as decoration or for water absorption. Moss has been used more frequently in the construction of "green roofs", a conservation effort to rescue the environmental impact of some buildings. Moss is used as an ingredient in peat, which can be used as a compost or as a fuel source in some homes. As moss grows, it tightly compacts the dead moss below it, creating bricks of moss that then can be burned or added to compost. Historically, moss has been used for bandaging wounds, and can sometimes be more absorbent than cotton!
Moss does not have roots. Instead, moss has root-like structures called rhizoids. Rhizoids are multicellular anchoring structures that help moss attach to objects. Rhizoids are not roots because they do not have the cellular structure to be able to absorb water and nutrients internally but together can form a mass of rhizoids that absorb water and nutrients externally by capillary action. Mosses can have dense rhizoids or they can be sparse, but the multicellular rhizoids in mosses are a key difference from other species in the bryophyte group; liverworts and hornworts do not have multicellular rhizoids. Only mosses do!
Mosses, because they are ancient plants and are very small, have flat structures often only one cell thick. This is vastly different from land plants, that have evolved to grow to huge sizes comparatively and have structures that are made up of many layers of cells. For example, true roots are multicellular and their large size allows for the uptake of water and nutrients internally, whereas the rhizoids of mosses take up water and nutrients externally. In addition, the leaves of mosses, as stated above, are often only one cell thick. Land plants however have leaves made up of many cells, often with different jobs and therefore structures, depending on what the plant needs and the species of land plant in question. Lastly, mosses can only grow a couple of inches high due to their lack of supportive tissues, whereas land plants can reach enormous heights because of their tissue structure.
Mosses are bryophytes, which are non-vascular plants with rhizoids instead of roots. Moss has several characteristics that differ from land plants in several ways. First, they have flat leaves, often one cell in width, and they grow close to the ground in clumps or sheets. Mosses differ from other bryophytes in that their rhizoids, or root-like structures, are multicellular. Rhizoids are not true roots because they do not uptake water and nutrients internally, but they function similarly to roots in that they help anchor moss to the surface on which it grows. There are many different types of moss depending on how they grow. Sheet moss, also called pleurocarpous mosses, are so named because they grow in long flat sheets, with only some species showing erect stems. Clumping mosses or cushion mosses, also known as acrocarpous mosses, grown in, you guessed it, clumps or cushions close to the ground, and often have tree-like tufts that extend upward. Haircap mosses tend to be taller and have thicker and longer rhizoids. Rock cap mosses grow on rocks and cannot live in direct sunlight. Mosses are sometimes called "early colonizers" in an ecosystem because they are some of the first species to inhabit an area that has been previously disturbed. Mosses play vital roles in the ecosystem such as water transportation, nutrient distribution, and soil retention.
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Moss is defined as any non-vascular plant with multi cellular rhizoids. Mosses are categorized into 8 classes and play important roles in ecosystems.
Moss is classified as any non-vascular plant with multicellular rhizoids. Mosses are characterized by their flat, often single-cell thick, leaves, low growth, and soft spiky texture.
Moss is not harmful to humans. Moss has several uses that are helpful to humans, such as in the production of peat moss, used as a fuel source or as a compost ingredient.
The purpose of moss in an ecosystem is to hold and transport water, aid in soil retention, help spread nutrient, and can even help decompose matter.
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