Moss

Moss
Kingdom:	Plantae
Phylum:	Bryophyta

Classes

There are three different classes of mosses within the phylum Bryophyta:

1. Peat Mosses
   • Sphagnidae
2. Granite Mosses
   • Andreaeidae
3. True Mosses
   • Bryidae

Mosses are a group of small, non-vascular, plants that are classified as Bryophytes. They are typically 0.2–10 cm tall and reproduce via spores. Mosses can commonly be found forming dense mats in wet and/or shady habitats. Some species are extremely resilient and tolerate many toxins, which is why they can also be found in a variety of areas including: urban brownfields, the cracks of roadways, and on the sides of buildings. Mosses provide a food source and habitat for macro and micro invertebrates and create microhabitats that are essential to some species of soil arthropods. [10]

Structure

Moss lacks vascular tissue, which is what other plants use to transport water and nutrients from their roots to their shoots. Since they lack this tissue, they have dissimilar anatomy to more morphologically complex plants. Instead of roots, members of Bryophyta have rhizoids, which hold their vegetative structures onto whatever substrate that they are growing on. Without vascular tissue, water is transported from cell to cell by diffusion. This is why these plants are so small. The gametophyte is the non-reproductive vegetative structure that photosynthesizes. The sporophyte is the reproductive structure that is essential to the dispersal of the moss's spores [1].

Life Cycle

Moss Life Cycle.

Moss have two parts to their life cycle. The first stage is the gametophyte, and this is the stage mosses will spend the majority of their life in. When haploid spores germinate they grow and mature, eventually developing male and female reproductive structures. The male structure is the antheridia and this produces sperm, while the female strucutre is the archegonia which will produce egg cells. The haploid sperm will swim through water to the archegonia-which releases a chemical signal to attract them-where the eggs will be fertilized and develop into diploid structures, this begins the sporophyte life stage. The sporophyte reproduces and via meiosis creates haploid spores, and the life cycle starts over again. Water is essential in the reproduction of moss, unlike the seed-bearing plants, which is one of the reasons why it must grow in moist environments [4].

Environmental Role

Mosses play an vital role in stabilizing soil, reducing erosion, and reducing the risks of flooding by absorbing excess water. Their rhizoids grip the ground and can hold on to clay, gravel, and sandy soil substrates. Along with absorbing moisture mosses are an important carbon sink and could potentially play an important role in combating climate change; additionally mosses can filter other pollutants like excess sediment and salt used on roadways. Within the local environments mosses also have the ability to create humid microhabitats, which allows plant seeds to germinate easily and soil arthropods to be able to flourish [2].

References

[1] Crandall-Stotler, B. J., and S. E. Bartholomew-Began. 2007. Morphology of Mosses (Phylum Bryophyta):3–13.

[2] Crooks, V. 2021, February 22. Bryophytes. Text, Smithsonian Tropical Research Institute. https://stri.si.edu/story/bryophytes.

[3] McHale, E. 2020, May 23. 7 interesting things about moss | Kew. https://www.kew.org/read-and-watch/moss.

[4] Carter, J. S. 2010, September 12. Mosses and Ferns. https://biologyclermont.info/wwwroot/courses/lab2/mosses%20intro.htm.