Seedless Vascular Plants: Ferns and Horsetails

• Ferns and horsetails belong to the seedless vascular plants.

Plant Phylums

• Nonvascular plants (bryophytes) include liverworts(9,000 species, phylum Hepatophyta), mosses (15,000 species, phylum Bryophyta), and hornworts (100 species, phylum Anthocerophyta).
• Seedless vascular plants include lycophytes (1,200 species, phylum Lycophyta), and pterophytes/monilophytes (12,000 species, phylum Pterophyta/Monilophyta).
• Gymnosperms include ginkgo (1 species, phylum Ginkgophyta), cycads (130 species, phylum Cycadophyta), gnetophytes (75 species, phylum Gnetophyta), and conifers (600 species, phylum Coniferophyta).
• Angiosperms include flowering plants (250,000 species, phylum Anthophyta).

Plant Evolution

• Land plants originated approximately 475 million years ago (mya).
• Vascular plants originated approximately 420 mya.
• Extant seed plants originated approximately 305 mya.

Comparing Plant Taxa

• Bryophytes, hornworts, and liverworts height are limited due to lack of vascular tissues.
• Bryophytes flagellated sperm are usually in moist environments
• Bryophytes gametophytes are the dominant generation
• Seedless Land Plants vascular tissues are the reason for larger, taller plants
• Seedless Land Plants flagellated sperm are usually restricted to moist environments.
• Seedless Land Plants sporophytes are the dominant generation

Vascular Tissue

• Vascular tissues facilitate the transport of fluids and nutrients throughout the plant.
• Xylem conducts most of the water and minerals, including dead cells called tracheids.
• Phloem consists of living cells and distributes sugars, amino acids, and other organic products.
• Water-conducting cells are strengthened by lignin, providing structural support.

Plant Parts

• Roots are organs anchoring vascular plants and absorb water and nutrients from the soil.
• Leaves are organs increasing the surface area of vascular plants, capturing more solar energy for photosynthesis.
• Lycophylls are leaves with a single vein.
• Euphylls are leaves with a highly branched vascular system.
• Not all underground structures are roots
• True Roots have large vertically growing root.
• Examples: carrots, radish, parsnips
• Tuberous roots are modified lateral roots for storage.
• Examples: sweet potatoes, yams
• Modified stems
• Corm
• Rhizomes
• Tuber
• Bulbs

Sporophyll and Spore Variations

• Sporophylls are modified leaves with sporangia.
• Sori are clusters of sporangia on the undersides of sporophylls.
• Strobili are cone-like structures formed from groups of sporophylls.
• Most seedless vascular plants are homosporous, producing one type of spore that develops into a bisexual (hermaphroditic) gametophyte.
• All seed plants and some seedless vascular plants are heterosporous.
• Heterosporous species produce megaspores, giving rise to female gametophytes, and microspores, which give rise to male gametophytes.

Seedless Vascular Plants

• Phylum Lycophyta includes club mosses, spike mosses, and quillworts.
• Phylum Pterophyta or Monilophyta include ferns, horsetails, whisk ferns, and their relatives.

Carboniferous Period

• Illinois coal mines have a forest floor as the mine ceiling.
• 306 million years ago, an earthquake buried a 4 square mile forest/swamp.

Ferns

• Ferns are the second-largest plant phyla after the angiosperms.
• Ferns include 12,000 species.
• Ferns have relatively little economic impact.
• Invasive species
• Limited food source
• Use in Horticultute
• Used for toxic waste removal

Horsetails

• Horsetails are found on all continents except Asia and Australia.
• There are 30 species in one genus of horsetails today.
• Horsetails were very diverse in the Carboniferous period, growing into 30 m high trees.
• Horsetails have very limited economic importance.
• Fern gametophytes are hermaphroditic.
• Fern gametophytes are a few millimeters in size.

This lesson explores seedless vascular plants, including ferns and horsetails. It also discusses plant phylums like bryophytes, lycophytes, gymnosperms, and angiosperms. The content further covers plant evolution timeline and comparison of plant taxa.