Moss thrives best in moist conditions. Thus all it ultimately needs to reproduce and continue its life cycle is water and sunlight. As long as it has sufficient access to both water and sunlight, moss can spread and multiply effectively.
Are mosses male or female?
There are both male and female mosses. Male mosses produce sperm through a cup that sits directly on top of them. It is this cup which makes them male and distinguishes their biology. You then have female mosses which have eggs that rest between their leaves.
It’s vital for the sperm from the male moss to come into contact with water. That’s because when the sperm reach maturity, they need water or moisture to swim to the eggs and fertilise them. After fertilisation has been achieved, the egg will produce a brown capsule. The reproduction process is then repeated so the moss is able to multiply and spread, and continues its life cycle - which we cover in more detail in the next section.
What is the life cycle of moss?
Moss differs from typical land plants when it comes to its life cycle. Instead of using seeds to reproduce, moss uses spores as it is a rootless species. The one thing moss does have in common with other plants is it also has alternating generations during the life cycle.
There are two alternating generations in mosses:
- The gametophyte (the first generation)
- The sporophyte (the second generation
The gametophyte forms when the sporophyte releases spores which start to divide. It has half the genetic material as the sporophyte. As previously mentioned, sperm relies on water to fertilise the egg, and in mosses the sperm cells will travel from one gametophyte to another through a thin film of water to achieve fertilisation. The egg develops into a sporophyte once it is fertilised, and the sporophyte will then produce spores.
The gametophyte is known as the dominant generation as the sporophyte relies on the gametophyte for its survival, as the gametophyte also supplements it with vital water and nutrients.
When moss spores germinate, they develop a protonema. This chain of cells often looks like an algal colony or a fern prothallus in appearance. A protonema forms in the very early stage of the moss life cycle. It allows individual or numerous stems to grow from it. In some cases leaves form from the protonema’s stem and develop into leafy-stemmed plants. If these plants form, the protonema is made redundant as the new plant becomes the dominant growth form. Although in a small number of moss species, the protonema can become dominant over the leafy growth.
The stem and leafy growth part of the moss is called gametophore, which fuses with the protonema to compose the gametophyte.
How do mosses reproduce and spread?
The spores which moss relies on for reproduction are the equivalent to a flowering plant’s seed. Spores are single-celled, just like the species which produces them. They inhabit a brown capsule which sits on the seta, and as they ripen they get released from this capsule to find areas which provide them with ample moisture for growth. The young moss that grows from these recently released spores will look like an unkempt mop of branching green hairs, from which buds will begin to form, allowing stalks and leaves to grow.
Moss can also reproduce through a process called fragmentation. The gemmae that forms on the leaves or branches on moss can break away and form new plants without having to be fertilised, therefore the process becomes asexual. This typically happens during the spring when new life tends to thrive.
Moss can also spread by releasing shoots that can easily inhibit cracks between paving stones or space in flower beds in gardens, and thus spread even further.
Moss can reproduce through a process called fragmentation
Where do mosses produce eggs and sperm?
Moss’s eggs and sperm develop on the gametophyte, which is why they are sometimes referred to as male and female gametes. Reproductive structures called antheridia and archegonia are housed in the gametophyte. These provide a vital incubation function for the fertilised egg which then develops into a sporophyte.
What are moss sporophytes?
Moss sporophytes can be defined as capsules that house the spores necessary for the reproductive cycle of moss. They are found on a seta, which is a stalk.
Most mosses will have sporophytes that have a defined mouth at the end of the seta, or the part which joins the capsule and the stem. This mouth serves an important function in acting as a passage which the spore is released through when it is ready to leave the capsule and continue the reproduction cycle to form a new moss plant. Some moss species, such as Andreaea, won’t possess these mouths or openings, although these are in the minority of moss species. They tend to exist in alpine and sub-alpine areas, in both the tropics and the polar regions. The spores leave the capsules through slits in the side rather than the mouth. In the moss species Archidium, the sporophytes experience spontaneous eruption, which is quite a fascinating process. This is due to the sporophytes in this particular species lacking slits in their side or mouths at the end of their stalks.
The moss reproduction cycle can be affected by these various ways in which spores are able to leave a capsule and continue the process - whether the spores leave from the mouth, the slits in the side, or leave through spontaneous eruption.