Ferns Honor

Nature Study

Requirements

1. What is the difference between ferns, trees, and flowers?

   Answer: Ferns: pteridophytes without seeds or flowers, they reproduce by spores in sori. Trees: woody plants with a trunk, leaves, fruits, and/or flowers. Flowers: the reproductive structures of angiosperms that produce seeds in fruits. Ferns are more primitive evolutionarily. — Botanical classification: ferns are pteridophytes (Polypodiophyta), an evolutionary group prior to seed plants. Trees can be angiosperms (flowering plants — mango, orange) or gymnosperms (without a true fruit — pine). Flowers are the sexual organs of angiosperms, containing the gynoecium and androecium for fertilization and the production of seeds in fruits. Ferns appeared in the Devonian (~390 million years ago) and formed the forests of the Carboniferous. There are currently ~12,000 species worldwide.

2. Where is the stem of ferns located? What part of it grows above the ground? In what environment is it most viable for a fern to grow?

   Answer: 1) Where the stem is located: the stem of the fern is the rhizome, which is underground or creeping on the surface of the soil. 2) What part grows above the ground: the leaves (fronds), divided into pinnae and pinnules, are photosynthetic and also reproductive (they carry the sori on their underside). 3) Most viable environment: moist, shaded places, rich in organic matter and with a mild temperature; tropical forests, the edges of waterfalls, and shaded banks are typical habitats. — Fern anatomy. Rhizome: an underground or creeping stem, it stores nutrients and generates new fronds. Fronds: characteristic leaves, usually compound (divided into pinnae, pinnules, and pinnulets). Growth: it starts coiled (crozier) and unrolls as it matures. Ideal habitat: high humidity (>70%), partial shade, drained clayey/organic soil. Humid tropical forests, hillsides, valley bottoms. Some species are adapted to dry environments (Pteridium aquilinum, bracken fern), but as an exception.

3. Explain how the reproduction of a fern occurs. Locate and describe 3 types of sori from 3 types of ferns.

   Answer: Reproduction by alternation: spores form a prothallus (gametophyte) that generates gametes; fertilization produces the sporophyte. Sori: 1) circular (Cyathea); 2) linear (Asplenium); 3) reniform (Polypodium). Each species has a characteristic distribution of the sori on the fronds for identification. — The life cycle of ferns is a classic example of gametophyte/sporophyte alternation. Spores (n) fall to the ground and germinate into a heart-shaped prothallus. Antheridia (male) and archegonia (female) release gametes. The antherozoids swim through the film of water to the egg cell. The zygote (2n) generates a new fern. Sori (sporangia) can be: round (Polypodium), oblong (Pteris), reniform (Dryopteris), in marginal lines (Adiantum), with an indusium or naked. Botanical identification uses the shape and position of the sori as a crucial taxonomic character.

4. How do the spores travel from the mother plant to a new location? How long does it take for a spore to develop into an adult plant? Demonstrate, through photographs or in nature, how young ferns differ from adult ferns.

   Answer: Spores travel by wind, water, or animals (minimal zoochory). Under favorable conditions: a prothallus in 1-2 weeks, fertilization in 1-2 months, a visible sporophyte in 6-12 months, an adult plant with sori in 2-3 years. Young ferns are coiled, in the shape of a bishop's crozier (croziers); adults have fully open fronds with visible sori on the underside of the leaves. — Spore dispersal is predominantly wind-borne — they are light (~30 µm) and travel up to kilometers. Some species have hydrochorous (water) or ornithochorous (birds) dispersal. Time: it depends on humidity and temperature. The crozier (or fiddlehead) is the characteristic young form that unrolls as it grows, known as circinate vernation. Adults are distinguished by: mature fronds, visible sori, final size. Edible: some young fiddleheads (Pteridium, tree fern) are consumed in Brazil and Asia.

5. Cite 3 types of ferns that we can use as medicinal remedies.

   Answer: 1) Maidenhair fern (Adiantum): expectorant, antitussive. 2) Tree fern (Cyathea): the stem is used in regional phytotherapy. 3) Wild fern (Polypodium): laxative, hepatoprotective. Use requires technical knowledge, correct dosage, and precise botanical identification by the Pathfinder. — Ferns have ethnobotanical use in various cultures. The maidenhair fern is traditional in European folk medicine, indicated for cough and bronchitis (the leaves in tea). Polypodium vulgare contains saponins, used as a medieval laxative. Equisetum (horsetail) is diuretic, with mineralizing silicon. Caution: many pteridophytes contain thiaminase (which destroys vitamin B1) or ptaquiloside (carcinogenic), so consume only after guidance. The tree fern is the raw material of xaxim (banned in Brazil for threatening the species). In professional phytotherapy, use only studied species.

6. Draw, photograph, and identify at least 10 types of ferns, including: scientific name, classification, and where it can be found.

   Answer: Identify 10 species (e.g.: Adiantum, Pteris, Asplenium, Polypodium, Cyathea, Nephrolepis, Polystichum, Dryopteris, Pteridium, Equisetum). For each: the scientific name in Latin, classification (family, genus), typical place (forest, garden, riverside). Present a herbarium or album with detailed photos/drawings. Research in the field, in botanical parks, on sites such as Flora do Brasil 2020. — Botanical identification: scientific name (binomial: Genus species), family (Polypodiaceae, Adiantaceae, Cyatheaceae), place. Herbarium: press the frond between newspaper sheets for 1-2 weeks, label it, glue it on cardstock. A digital photo replaces this in modern projects. Resources: Flora do Brasil 2020 (Reflora), CNCFlora, the PlantNet app, the books 'Pteridófitas do Brasil' (Prado and Sylvestre). A visit to Botanical Gardens (Rio, SP) or preserved Atlantic Forest complements direct observation of the species in nature.

7. Besides common ferns, there are plants similar to ferns that are known as club mosses and horsetails. Be able to recognize 2 club mosses and 1 horsetail. Explain their similarities to ferns.

   Answer: Lycopodium: small with scale-like leaves, sporophylls in terminal strobili. Equisetum: a hollow stem articulated at nodes, with sporangia-bearing cones. Similarities to ferns: pteridophytes without seeds/flowers, they reproduce by spores, alternate generations, and are ancient vascular plants. — Club mosses (Lycopodiopsida): rare today, their ancestors formed the forests of the Carboniferous (300 million years). Species: Lycopodium clavatum (stag's-horn club moss), Selaginella. Horsetails (Equisetidae): the only living genus is Equisetum, with the 'horsetail' (Equisetum arvense, E. giganteum). A hollow silicified stem, formerly used to polish metals. All are pteridophytes: no flowers, no seeds, with conducting vessels. Differences: club mosses have microphylls (1 vein); ferns and horsetails have megaphylls. Botanical importance: living witnesses of ancient plant evolution.