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Mosses

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  • Last Updated : 04 Dec, 2022
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Plantae is the plant kingdom that contains all plants on Earth. They are eukaryotes with many cells. The presence of the cell wall, an impermeable wall that surrounds the cell membrane, distinguishes them. Chlorophyll, a green pigment found in plants, is essential for photosynthesis. As a result, they consume in an autotrophic manner. Because of its immensity, the plant kingdom is divided into various subdivisions. Understanding the categorization of the Kingdom Plantae is the first step in understanding plants. Understanding the fundamentals makes it easier to learn everything there is to know about each plant.

According to Whittaker’s Five Kingdom Grouping, all living things are classified into five kingdoms: Protista, Monera, Fungi, Plantae, and Animalia. If you want to learn more about plants, you must first grasp the Kingdom Plantae, sometimes known as the Kingdom of Plants. The variety of plants seen here will astound you. Both the smallest plants, such as algae and the largest plants, such as the Sequoia, may be seen. Flowers are an extremely appealing organelle found in certain plants but not others. It is only a thalloid structure in basic plants, but some plants have an appropriate root system, shoot system, and leaf structure.

Plant Kingdom Classification

  1. Plant Body: Whether or whether the body has well-differentiated components.
  2. Vascular System: Whether or not the plant has a vascular system for transferring chemicals.
  3. Seed development: Whether or not the plant enables flowers and seeds to develop, and if so, whether or not fruits grow around them.

Mosses

Mosses are non-vascular, flowerless plants that belong to the Bryophyta taxonomic group. The parent group bryophytes, which includes hornworts, liverworts, and mosses, is also known as Bryophyta. Mosses usually form dense, green mats or clusters in moist or shady locations. Individual plant leaves are generally only one cell thick, attached to a stem that may or may not have branches, and serve a very limited function in water and nutrient transfer. Despite the fact that certain species contain conducting tissues, these tissues are often undeveloped and visually separate from vascular plant tissue. Mosses do not produce seeds, but rather sporophytes, which are unbranched stalks capped with spore-containing capsules.

Mosses are often confused with lichens, liverworts, and hornworts. Mosses are classified as “non-vascular” plants, along with hornworts and liverworts. Despite the fact that many mosses have sophisticated vascular systems, haploid gametophyte production is the most important stage in the life cycles of all of these plants. In contrast, in the pattern of all vascular plants, the diploid sporophyte generation predominates (seed plants and pteridophytes). Despite their superficial resemblance to mosses, lichens are unrelated to them, despite common names such as “reindeer moss” or “Iceland moss.”

Moss

 

Characteristics of Mosses

  • Mosses are non-vascular plants of the order Bryophyta, which also contain terrestrial plants. 
  • They are generally herbaceous (non-woody) plants that absorb water and nutrients via their leaves and trap carbon dioxide and sunlight to make food through photosynthesis. Except for Takakiopsida, no known moss develops mycorrhizal. 
  • They differ from vascular plants in that they lack water-bearing xylem tracheids or vessels. 
  • The most common step of the life cycle, as in liverworts and hornworts, is the development of haploid gametophytes. In contrast, in all vascular plants (seed plants and pteridophytes), the tendency favors the development of diploid sporophytes. 
  • Mosses lack blossoms and reproduce by spores rather than seeds.
  • The stems of moss gametophytes can be straight or curved, simple or branching. Takakiopsida, Sphagnopsida, Andreaeopsida, and Andreaeobryopsida are early diverging classes that either lack stomata or have pseudostomata that do not produce pores. Stomata have disappeared from the remaining classes more than 60 times. 
  • Their leaves are straightforward, frequently consisting of just one layer of cells with no internal air gaps and larger midribs. Although they lack true roots, they are anchored to their substrate by threadlike rhizoids. Through their rhizoids, mosses do not take up water or nutrients from their substrate. Their multicellular rhizoids allow them to be recognized from liverworts (Marchantiophyta or Hepaticae). 
  • Mosses are distinguished from polysporangiophytes, which are all vascular plants, by the sporangia or capsules that contain their spores that are carried individually on long, unbranched stems. 
  • The short-lived spore-bearing sporophytes (i.e., the diploid multicellular generation) are often photosynthesis-capable but rely on the gametophyte for water and most or all of their nutrition. 
  • Additionally, unlike liverworts, the majority of mosses have spore-bearing capsules that expand and mature prior to their stalks elongating. This contrasts with the majority of mosses. 
  • Other characteristics are not always present in all mosses and liverworts, but the existence of a clearly distinct stem and straightforward, non-vascular leaves that are not grouped in three ranks all indicate that the plant is a moss.

Classification of Mosses

The oldest terrestrial plants are mosses. Historically, the phylum Bryophyta was used to classify all mosses. The True mosses, sometimes known as the Musci, were one of the three groups that made up the Bryophyta. A novel taxonomy that places the Bryophyta as a subgroup of the Mosses has recently been proposed due to the differentiation of the thallus and, in particular, the sporangia. This most recent understanding distinguishes the following groups:

  1. Liverworts (Hepatophyta)
  2. Hornworts, or Anthocerotophyta
  3. Bryophyta sensu stricto (= True mosses)

Liverworts

The liverworts, with their flat thallus that lies on the ground and bears rhizomes that connect to the soil, are the most basic mosses. There are almost usually oil cells in the thallus. There are gametangiophores in the form of umbrellas that are either male (referred to as antheridiophores; phore means to carry) or female (called archegoniophores). The one-egg cell-bearing female archegonia opens towards the bottom surface, whereas the male antheridia open toward the upper portion. The archegoniophore’s margins are downwardly curled in a small curvature (like the cap of mushrooms). The adult sporangium protrudes slightly from the base of the sporophyte as the seta, the stalk at its base, grows. The grooves on the spore caps allow the spores to be discharged within a few hours of the caps being opened. Example: Marchantia

Hornworts

Liverworts and hornworts are similar, but hornworts appear to be more like actual plantlets. There are just one or two big chloroplasts in each cell, and they never have oil cells. In the upper portion of the thallus, the gametangia are recessed. The term “Hornworts” refers to the adult sporangia (sporophyte, 2n) that protrude above the surface as little horns. Strong outgrowths from the seta, the sporophyte’s base, create these horns. After the grooves in the sporangium open, the spores can continue to disperse for a few weeks. There are a little over 100 different species. Although they are not yet fully established, they are fairly uncommon in the Netherlands.

True Mosses

Despite not having actual stems, leaves, roots, or tissues, the architecture of real mosses has a unique stem and leaf-like look. At the very top of the male and female gametophytes, the gametangia form. The zygote turns into a sporophyte after fertilization, but it stays connected to the female gametophyte. The sporophyte consists of a seta and a capsule with an operculum as a cap. The teeth at the edge of the capsule opening (peristome) become evident as the capsule ripens and the operculum separates. The sporangium extends above the other plantlet sections due to the seta’s extension, leaving it open to the wind. Spore-producing cells go through meiosis inside the capsule to create haploid spores. These spores can take days to disperse. The Bryophytes’ largest and most prevalent phylum is by far the true mosses. The Netherlands is home to more than 500 species. Sphagnum, Polytrichum, and funaria, as examples.

Types of Mosses

Peat moss (Sphagnopsida)

Sphagnopsida, sometimes known as peat moss or sphagnum moss, is the first moss group we’ll examine. Numerous mosses that live in moist, bog-like regions and frequently form sizable, spongy clumps are part of this category. These mosses are frequently utilized as mulch to improve the soil but can also make the soil acidic. Plants that thrive in acids, such as blueberries and cranberries, are often found growing alongside peat moss. One of the various types of plants that can decompose into peat is peat moss. One of the many uses for peat is as a fuel substitute for cooking and heating homes. In truth, peat has been gathered and utilized for this purpose for millennia in some regions of Europe.

Andreaeopsida (Rock moss or Lantern moss)

The following class, Andreaeopsida, is also known as lantern mosses or rock mosses and grows on rocks. Numerous species grow in tufts and are black in color. The labels “rock” and “lantern” are appropriate given that a portion of the plant might resemble a lantern and that it grows on rocks. Members of the Andreaeopsida can be found growing at high latitudes and in chilly environments.

Polytrichopsida

The Polytrichopsida is a pioneering family of plants that can thrive in challenging environments, and they make up the third group of mosses we are showcasing. When there has been a disturbance, such as a flood or fire, pioneer species are the first to reappear in the region. This category has a wide range of species, including the tallest moss in the world, Dawsonia superba, as well as small and large species.

Bryopsida

The largest group of mosses, Bryopsida, which comprises 95% of all moss species, is the last group of mosses we’ll look at. This group is diverse, yet they all share a toothed spore capsule as a common feature. What? The capsule merely serves to preserve the spore, which disperses and develops into new mosses. When the time comes for the spores to disperse, the “ring of teeth” on these spore capsules helps them do so.

Life Cycle of Mosses

The haploid gametophyte and the diploid sporophyte, which is known as alternation of generation, alternate during the life cycle of mosses. The haploid gametes produced by the male and female gametophytes combine to form a zygote, which then develops into the diploid sporophyte. The haploid spores that the sporophyte generates later develop into the haploid gametophyte.

Gametophyte

  • The gametophyte generates the male and female sex organs at the terminals of structurally distinct stems and leaves.
  • The female sex organ is referred to as an archegonium, and it is only one cell thick and bottle-shaped. Perichaetium leaves, modified leaves, shield them.
  • The male sex organ, also known as the antheridia, is a small, club-shaped structure with stalks. They are shielded with perigonium, modified leaves.
  • Antherozoids, which have a biflagellate shape and are released when the antheridium reaches maturity move across the water when fertilizing with an archegonium’s egg.
  • The second life phase of mosses, the sporophyte, results from the formation of a diploid zygote.
  • The calyptra, which eventually divides to produce the archegonium, serves as a protective structure for the capsule in the sporophyte.

Sporophyte

  • A diploid sporophyte develops from a diploid zygote. A sporophyte is made up of a foot, a seta—a long stalk—and a capsule with an operculum on top.
  • The sporophyte divides through mitosis and stays connected to the gametophyte like a parasite, depending on it for food and water.
  • Spore-producing cells in the capsule go through meiosis to create haploid spores.
  • Peristomes, which resemble teeth, are featured on the capsule that stops spores from slipping off when it is wet.
  • The operculum and peristome fall off when the conditions are right, or when the spores are prepared to be spread, and the spores are then dispersed in the surrounding environment.
  • Spores that land on moist, damp ground germinate to produce a protonema, which are filamentous structures that resemble threads. The gametophyte, which completes the life cycle, develops from the proteome as a transitional structure.

Economic Importance of Mosses

  1. Florists utilize them to decorate homes.
  2. Sphagnum was employed as a bandage during World War I because of its ability to absorb water.
  3. In the past, it was also employed as a fire extinguisher.
  4. Peat, a layer of moss that has been collected, is burned as fuel.

FAQs on Mosses

Question 1: Do mosses belong in the plant kingdom?

Answer:

Mosses are non-flowering plants that release spores and have stems and leaves but no actual roots. They are ancient plants. Mosses are categorized as Bryophyta (bryophytes) in the plant kingdom, along with their relatives the liverworts and hornworts..

Question 2: What stage of the moss life cycle produces spores?

Answer:

In the moss life cycle, sporophytes produce haploid spores.

Question 3: What aspects of their life cycles do moss and ferns have in common?

Answer:

Water is necessary for fertilizing both ferns and mosses. Without water, the sperm cannot reach the egg.

Question 4: What two kinds of mosses are there?

Answer:

Pleurocarpous and Acrocarpous are two subgroups of moss that can be distinguished. Although there are other differences between the two groups, the main one is that acrocarpous grows upright while pleurocarpous moss spreads out like a carpet.

Question 5: What are the seven moss categorization levels?

Answer:

According to the 2000 classification system, there are six subclasses within the phylum Bryophyta: Takakiopsida, Sphagnopsida, Andreaeopsida, Andreaeobryopsida, Polytrichopsida, and Bryopsida.


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