Personally I really like life cycles and I think that they are critical to understanding plant biology. The life cycle of mosses is something that I think about on a daily basis, but I know that is a little out of the ordinary. Below, I introduce the moss life cycle using the moss species that I study, Funaria hygrometrica, so that those of you who aren't as intimately involved with plants would have a good summary of how it all works.
I am going to break this topic down into a few posts since it is a lot of information to digest at once.
Starting on the far left (9 o'clock) is an image of the leafy green gametophyte (aka. the moss plant). This portion of the life cycle is haploid, meaning that it has one set of chromosomes per cell. It is different from the large photosynthetic portion of most plants which is diploid with two sets per cell. It is photosynthetic, capturing sunlight water and carbon dioxide to make sugars.
The function of the gametophyte in the life cycle is to make gametangia. Gametangia (antheridia- male & archegonia - female) are the sexual reproductive structures. Thus the gametophyte is the sexual stage of the life cycle.
At 11 o'clock are two images of these sexual reproductive organs that are produced by the leafy gametophyte. To the far left are the antheridia and below toward the right is an archegonium.
The antheridia are the dark brown structures that each produce hundreds of sperm. The single thin structure is an archegonium which contains only one egg per. The sperm and egg cells are also called gametes.
So we have gametophytes (mossy plant) that make gametangia (antheridia & archegonia) which produce gametes (sperm & egg). All of these structures are haploid and are produced by mitosis. In this process of cell division there is no change in the number of chromosomes per cell .
If you have any tips or comments on learing about the life cycle of mosses, feel free to share in the comments section. Stay tuned for the next installment of the life cycle.