Land Plants – The Mosses www.onacd.ca

Mosses: Division Bryophyta Mosses are members of the division Bryophyta and there are approximately 12000 species that grow all over the world. They are soft plants that grow in masses or clumps and typically grow between 1 and 10 cm in height.

Mosses: Division Bryophyta Mosses do not have flowers or roots and are non-vascular plants. Grow in damp, shady locations. Commonly found in wooded areas and near streams

Mosses: What they don’t have No water transporting network. Instead, water moves by osmosis from cell to cell This is one reason why mosses never grow tall No protective surface to stop water from evaporating from their cells “leaves” are only one cell thick, therefore if the air is dry the plant will quickly dry out No true roots Instead they have structures called rhizoids that anchor the plants into the ground

Characteristics shared by moss Mosses need water because of their small size, thinness of their tissue, lack of waxy cuticle to hold water in, and for sperm to swim in during fertilization Have a gametophyte dominant life cycle (haploid, 1N) The sporophyte stage is short-lived and is dependant upon the gametophyte Can be dioicious (separate male and female plants) or monoicious (both male and female on the same plant)

Moss Life Stages The moss life cycle includes alternation of generations in which there are two life forms: The dominant gametophyte and the short-lived sporophyte. See diagram to the right.

Moss Sporophyte The sporophyte grows out of the gametophyte after fertilization of egg and sperm has taken place and can take from ¼ - ½ a year to develop. It is made up of a long stalk (seta) , a capsule (calyptra) and a cap (operculum). It produces spores that are eventually expelled and will grow into new gametophytes. (Above: two different types of moss sporophytes. Note the difference in shape)

Sporophyte takes ¼ to ½ a year to develop Moss Life Cycle Sporophyte takes ¼ to ½ a year to develop The spores develop into a protonema which can look like a mass of filaments or can be thallus like Bi-flagellated sperm need water in order to swim from antheridia down the longs necks of the archegonia to the eggs

Moss Reproductive Structures Mosses have specialized structures that protects the gametes from drying out Antheridium - a structure that produces tiny flagellated sperm (male) Archegonium – a structure that produces eggs (female)

Moss Life Cycle (Step by Step) Moss plant produces sex cells - gametes (sperm or egg). Antheridium produce flagellated sperm; archegonia produce eggs Sometime both gametes are produced on the same plant Both gametes are produced by mitosis and are haploid Sperm swim through water until they are able to reach the egg. Fertilization will occur when sperm and egg fuse When an egg and sperm fuse, this is called syngamy and a diploid zygote is produced After the egg is fertilized it now has two sets of chromosomes and grows right there on top of the gametophyte. Although this new plant is not called a gametophyte it is called a sporophyte.

Moss Life Cycle (Step by Step) The sporophyte is supplied with water and nutrients by the gametophyte. Moss sporophytes cannot live independent of the gametophyte upon which they grow The sporophyte is made of a “foot” that is stuck in the gametophyte, a long stalk and a capsule that looks like a salt shaker. Inside the capsule, haploid spores are produced by meiosis The capsule then ripens and opens. Wind then blows the spores away from the sporophyte The spores then grow into a mass of tangled green filaments called a protonema As the protonema grows, it forms rhizoids that grow into the ground and shoots that grow into the air and become gametophytes.

Ecological Roles of Mosses Create organic matter and make local habitats more suitable for seed bearing plants Water retention Land stabilization Shelter and humidity for a diverse group of invertebrates Integral part of the food web

Economical Roles of Mosses Florist trade Sphagnum moss (see left) is a key ingredient in peat moss. Peat mosses accumulate in deposits that may be several hundred meters thick Used as fuel, as a soil additive and in the production of scotch whiskey In world war II sphagnum moss was used as first-aid dressings on soldiers wounds