The pteridología is the study of ferns, plants of the division Pterophyta seeds and flowers. Unlike trees and plants, ferns have reproductive cells called haploid spores.
Haploid spores grow as small organisms that undergo fertilization and grow the fern plant directly out of the haploid gametophyte, similar to the stem that grows out of a moss.
Fern
Spores are the reproductive system of ferns. The largest part, which is considered to be the fern, is the sporophyte.
The gametophyte is a small green stem from which the sporophyte grows. Ferns are still tied to an aquatic environment in which once a spore grows on a protrusion there must be enough moisture for the egg on the protrusion to be fertilized with the fern flagellum.
The production of many more propagules increases the presence of ferns and the dominance of this plant class. In addition to having a larger sporophytic generation, ferns have many important adaptations that increase their capabilities over and above mosses, flowering plants, and trees.
Ferns have roots that, unlike moss rhizoids, not only anchor but absorb nutrients. They are vascular plants, with lignified vascular tissues that allow active water transport.
At some point in the past, ferns and fern trees were the most advanced plant life and grew even larger than ferns today. There were no flowering plants in the early Cretaceous; the earliest dinosaur forests were made of ferns.
Relevant aspects of pteridology
Pteridology as a science has a wide variety of areas of study and has particular characteristics that must be studied for a complete understanding of its function and importance. Here are the most relevant aspects of pteridology.
Evolution
Ferns have a great advantage over mosses in their vascular tissue. They can grow taller and can exist in more diverse environments. This is a trend that will continue in evolution, eventually leading to the emergence of generations of sporophytes as large as sequoia trees.
But if ferns are much better suited to survival, why are there still mosses? And if a larger generation of sporophytes is more suitable, why haven't the redwoods become dominant enough to eliminate the ferns?
Pteridology dictates that: while there are clear benefits to a larger generation of sporophytes, in some recurring natural situations natural selection favors mosses over ferns or ferns over trees.
The spores are better spread by the wind than many seeds, for example. Thus, while in the long term the protection of a seed allows seed plants to be dominant on the planet, in many situations the lightness and transport of a spore remains more efficient in the propagation of ferns.
The evolutionary character of ferns is due to their physical and biological properties, these properties are studied by pteridology.
Ecology
The stereotypical picture of ferns growing in the moist corners of shady forests is far from a complete picture of habitats where ferns can be found.
The various species of ferns live in a wide variety of habitats, from remote mountain elevations to dry desert rocks, bodies of water, or open fields.
Ferns in general can be thought of as specialists in marginal habitats, as they often grow in places where various environmental factors limit the success of flowering plants.
Some ferns are among the hardiest weed species in the world, including the fern that grows in the Scottish highlands or the mosquito fern (Azolla) that grows in tropical lakes. Both species form large aggressive weed colonies.
There are four particular types of habitats where ferns grow: moist and shady forests. Cracks in rocks, especially when protected from the sun. Acidic wetlands including swamps. Tropical trees where many species are epiphytes, that is, they rely on another plant to grow.
Many ferns depend on associations with mycorrhizal fungi. Some ferns only grow within specific pH ranges.
For example, the climbing fern (Lygodium palmatum) of eastern North America only grows in moist, intensely acidic soils. While the bladder bulbil fern (Cystopteris bulbifera) is only found in limestone.
Spores are rich in lipids, proteins, and calories. For this reason, some vertebrates feed on spores.
The field mouse (Apodemus sylvaticus) has been found to eat the spores of the mattress fern (Culcita macrocarpa) and the New Zealand bat Mystacina tuberculata, also eat fern spores.
Taxonomy
Of the pteridophytes, ferns represent almost 90% of the existing diversity. Smith et al. (2006), classified the higher-level pteridophytes as follows:
- Tracheophyta division (tracheophytes) - vascular plants.
- Euphyllophytina Branch (Euphilophytes).
- Infradivision (monilophytes).
- Infradivision Spermatophyta - seed plants, ~ 260,000 species.
- Lycopodiophyta branch (lycophytes) - less than 1% of existing vascular plants.
Where the monilophytes comprise around 9,000 species, including horsetails (Equisetaceae), common ferns (Psilotaceae) and all leptosporangiate and eusporangiate ferns.
Economy and importance of ferns
Ferns are not as economically important as seed plants but are also of considerable importance in some societies.
Some ferns are used for food, including the fiddlehead fern (Pteridium aquilinum), ostrich fern (Matteuccia struthiopteris), and cinnamon fern (Osmundastrum cinnamomeum). Diplazium esculentum is also used by some people in tropical areas as a food.
King fern tubers are a traditional food in New Zealand and the South Pacific. Fern tubers were used as food 30,000 years ago in Europe.
The Guanches used fern tubers to make gofio in the Canary Islands. There is no known evidence that ferns are poisonous to humans. The rhizomes of the licorice fern were chewed by the natives of the Pacific Northwest for their flavor.
Some ferns also have various medical uses such as internal cleansing and the purification of heavy metals in the liver.
References
- Parameswaran Krishnan Kutty Nair. (1991). Aspects of Plant Sciences: Perspectives in pteridology, present and future: Professor SS Bir commemoration volume. Google Books: Today & Tomorrow's Printers and Publishers.
- N. Bhardwaja, CB Gena. (1992). Perspectives in pteridology: present and future: Professor SSBir commemoration volume. Google Books: Today & Tomorrow's Printers & Publishers.
- C. Verma. (1987). Pteridology in India: a bibliography. Google Books: Bishen Singh Mahendra Pal Singh.
- David B. Lellinger. (2002). A Modern Multilingual Glossary for Taxonomic Pteridology. Google Books: American Fern Society.
- Pravin Chandra Trivedi. (2002). Advances in Pteridology. Google Books: Pointer Publ.