Vascular Plants: Clubmosses, Horsetails, and Rhyniophyta
Rhyniophyta
- The most primitive vascular plants.
- Extinct, grew in shallow waters in the Paleozoic era.
- They did not have true roots, but a rhizome – an underground stem (podzemok) with rhizoids (pakorienky).
- The stem was photosynthetic, lacking leaves.
- It branched into telomes (telómy).
- Isomorphic metagenesis: sporophyte and gametophyte looked alike.
Clubmosses
- Botanists first thought they resembled moss, which is why “moss” is in the name. The “club” part of the name comes from the club-like shape of the plant’s fertile stalk.
- Clubmoss is categorized with ferns and horsetails because it is spore-producing and has a vascular system (a system to transport fluids and nutrients). While moss also reproduces by spores, it doesn’t have a vascular system.
- In the Paleozoic era, they were herbs or trees (up to 30 m tall).
- Nowadays, they are herbs 5-20cm in height.
Structure of the Body of Sporophyte:
- Stems are branched (forked) into two parts.
- Rhizome and roots are present.
- Leaves are either sterile (green, needlelike, photosynthetic) or fertile (create strobili, sg. strobilus, výtrusný klas).
Structure of Gametophyte:
- Long-lived, residing underground for several years.
- About one square cm.
- S>G sporophyte is larger than gametophyte => heteromorphic metagenesis.
Sporophyte and gametophyte stages of clubmoss are slow-going. A spore that germinates into a prothallus (gametophyte stage) can lie dormant for up to seven years. Once the prothallus begins to grow, it can take up to 15 years to reach sexual maturity.
- Only when water is available can the egg and sperm cells released make contact and grow into the visible sporophyte stage. Another five years may be needed for the sporophyte to produce the visible club-like fertile stalks called strobili that release the spores. Therefore, from spore to spore may take 20 years.
- Once the plant is established, spores are plentiful and they have been sought after for hundreds of years. The spores have a unique combination of properties: uniform in size, high oil content, and water-repellent.
Horsetails
- Tall trees in Paleozoic times (up to 15-30m).
- Nowadays – herbs, perennials (trvalky).
- The genus name of Equisetum comes from the Latin “equus” (horse) and from Latin “seta” (animal hair, bristles), which refer to the stiff bristle hairs of the mane on a horse, which is like the horsetail.
Structure of the Body of Sporophyte:
- Ribbed hollow stem.
- Stem is divided into nodes (uzly) and internodes (články) -branches arranged in whorls (praslen).
- Feathery green leaves (photosynthesis).
- Sporangia are in a strobilus (výtrusný klas).
- Underground rhizome with roots.
Structure of Gametophyte:
- Small (approximately 5 mm), bisexual, heart-shaped plant called a prothallus.
- Heteromorphic metagenesis.
Each spore has four ribbon-like structures called elaters (haptery – rozhadzovače výtrusov) attached.
- When the spore is wet, the elaters are tightly coiled around the spore, but as the spore dries, they unfurl. This coiling and uncoiling helps the spores to spill out of the sporangium, and once on the ground, allows them to “walk”.
Field/Common Horsetail (Praslička Roľná)
It has two types of stem:
Fertile Stem (fertilná = plodná stonka, jarná byľ)
- Grows from the rhizome in early spring.
- Pale brown, non-photosynthetic stem.
- It is topped by a strobilus – used for reproduction.
Sterile/Vegetative Stem (sterilná = neplodná stonka, letná byľ)
- Green, covered with leaves.
- Serves for photosynthesis = production and storage of glucose (as a starch) – grows in summer.