Page 3: Horsetails - Structure and Life Cycle

Horsetails, also known as scouring rushes, have a unique structure and reproductive cycle that sets them apart from other pteridophytes.

Key features of horsetails:

• Scale-like leaves that do not perform photosynthesis
• Photosynthetic function is carried out by the stem
• Jointed structure of aerial stems and rhizomes
• Spore-producing cones at the tips of stems or on separate fertile shoots

The life cycle of horsetails involves both underground and above-ground phases. The sporophyte produces spores in cone-like structures, which then develop into small, green, dioecious gametophytes.

Vocabulary: Strobilus - The cone-like structure at the top of horsetail stems that contains spore-producing sporangiophores.

Highlight: Horsetails have separate fertile and sterile shoots, with the fertile shoots appearing in spring to release spores.

Example: The field horsetail (Equisetum arvense) demonstrates the cykl rozwojowy skrzypu polnego (life cycle of field horsetail) with its distinct fertile and sterile shoots.

Definition: Sporangiophore - A specialized structure in horsetails that bears sporangia and is arranged in whorls within the strobilus.

Page 1: Introduction to Pteridophytes

Pteridophytes are a group of plants that includes ferns, horsetails, and club mosses. They share similarities with bryophytes but have distinct characteristics that set them apart.

Key features of pteridophytes:

1. They are vascular plants with true tissues.
2. Their life cycle is dominated by the sporophyte generation.
3. They reproduce via spores and require water for fertilization.

The life cycle of pteridophytes involves gametophytes, which can be monoecious (hermaphroditic) or dioecious (separate male and female). Monoecious gametophytes have mechanisms to prevent self-fertilization, such as developing antheridia and archegonia at different times.

Pteridophytes can be homosporous (producing identical spores) or heterosporous (producing microspores and megaspores). Homosporous plants can develop both monoecious and dioecious gametophytes, while heterosporous plants always produce dioecious gametophytes.

Vocabulary: Gametophyte - The haploid, gamete-producing phase in the life cycle of plants.

Highlight: Pteridophytes have evolved strategies to prevent self-fertilization, which is crucial for maintaining genetic diversity.

Example: In heterosporous pteridophytes, microspores develop into male gametophytes, while megaspores develop into female gametophytes.