FERN LIFE CYCLE: THE 7 MAIN PHASES - BIOLOGY - 2025

In the life cycle of the fern, it presents two well differentiated stages: sporophyte and gametophyte, also called diploid and haploid phases. The diploid phase is asexual and the diploid sexual.

Ferns are plants that are descended from the oldest on Earth - they date back to the Paleozoic era.

They do not reproduce by seeds or flowers. Its reproduction occurs through the leaves, called fronds.

The fronds differ from the leaves themselves because they perform the reproductive function.

They are fragile, thin, and tend to dehydrate and dry out easily. When the fronds begin to emerge they are tightly curled, and they begin to unscrew as they grow.

Ferns are characterized by being vascular plants, since their reproduction is generated through spores.

Vascular tissues carry food, water, and minerals. These are capable of primary growth, this means that they grow upwards. On the contrary, they do not increase in diameter, which is what is called secondary growth.

The 7 phases of the fern life cycle

1- Sporophyte

The sporophyte is the fern that is seen with the naked eye, formed by leaves called fronds. Small dots called sori appear on the back of these leaves.

The human eye sees them as small brown dots. In some species of fern they are not seen because they are covered by a membrane called indusium.

2- Creation of spores

The sporangia are points that form the sori, and are responsible for producing spores. They are covered by a ring of sterile cells, but inside are the cells that make up the spores.

The spores are created through the process of meiosis.

3- Stomium

When the sporangium cells are mature, the sterile eye dehydrates and contracts, opening and releasing the spores.

4- Germination: generation of the gametophyte

The spores germinate when falling in a very humid space and originate the gametophyte, which is heart-shaped.

The gametophyte is a lamina that in some cases has rhizoids, a structure equivalent to the root through which it is attached to the ground.

5- Development of gametangia

The structures that house the gametes develop on the gametophyte: the gametangia. The male gametangia are called antheridia, and the female ones are called archegonia.

So, the female organs contain the egg cell and the male organs contain the sperm.

6- Fertilization

The sperm fertilize the egg cell and the union forms a zygote. The antheridium opens and the male gamete swims toward the female gamete. For this reason it is necessary that the environment is humid.

The zygote will grow and form a sporophyte through mitosis, or cell division. The sporophyte depends on the gametophyte for its food.

7- Creation of the new sporophyte

The sporophyte produces root, stem, leaves and develops, and the gametophyte is consumed and disappears. The sporophyte continues its independent life.

So the sporophyte is the asexual generation and the gametophyte is the sexual generation.

References

1. Haufler, Christopher H. Homospory 2002: An Odyssey of Progress in Pteridophyte Genetics and Evolutionary Biology. Bioscience52. 12 (2002): 1081-1094.
2. Haig, David and Wilczek, Amity. "Sexual conflict and alternation of haploid and diploid generations." Philosophical Transactions of the Royal Society B: Biological Sciences 361. 1466 (2006): 335-343.
3. Editor (2010) Life Cycle of a Fern. 12/09/2017. sas.upenn.edu
4. Klekowski, Edward. "Plant clonality, mutation, diplontic selection and mutational meltdown." Biological Journal of the Linnean Society79. 1 (2003): 61.
5. Krogh. Biology: A Guide to the Natural WorldUpper Saddle River: Prentice Hall, 2005.