The Bryophytes

Mosses, Liverworts, & Hornworts Chapter 22

• •

Evolution of Land Plants

Land plants evolved from green algae – Evidences: • Share chemical & metabolic traits • Same photosynthetic pigments • Store excess carbohydrates as starch • Cellulose is a major component of both cell walls The most direct ancestors of plants are the Charophytes “stoneworts”

Adaptations for Life on Land

• •

Cuticle

– Waxy covering over the epidermis of aerial plant parts – Prevents desiccation “water loss”

Stomata

– Small pore in the plant epidermis – Allows gas exchange for photosynthesis

The Plant Life Cycle

•

Alternation of Generations

Haploid (gametophyte) stage alternates with a diploid (sporophyte) stage in the life cycle

Plant Reproduction

• Gametangia – Plant sex organs – Consists of 2 parts: • A protective outer layer of sterile (non-reproductive) cells • Gametes – sperm or egg cells.

• • Male Gametangia = Antheridium – Bears numerous sperm cells Female Gametangia = Archegonium – Bears a single egg cell

Moss Gametangia

Antheridium – Male Archegonium – Female

4 Main Groups of Plants

1.

2.

3.

4.

– – – Bryophytes – Nonvascular; spores Mosses Stoneworts Liverworts – Seedless vascular plants; spores Club Mosses – Ferns, whisk ferns, and horsetails – Gymnosperms; seeds Conifers – Cycads – Ginkgoes – Gnetophytes – – Angiosperms “Flowering plants”; seeds Monocots Eudicots

Quiz!

• What is vascular tissue?

• What are the two types of tissue that make up the vascular tissue system? • What does each tissue do?

Bryophytes

• • • • • “moss plant” Nonvascular plants – Cannot extensively transport water, sugar, and minerals – Rely on diffusion and osmosis to obtain water and dissolved nutrients – Typically small Some have a cuticle Some absorb water directly through leaf surfaces Most require moist environments to reproduce

Bryphytes

• • 3 Phyla of Bryophytes 1. Phylum Bryophyta: Mosses 2. Phylum Hepatophyta: Liverworts 3. Phylum Anthocerophyta: Hornworts – All are Gametophyte dominant Spend most of their life cycle in the gametophyte stage

Mosses

• • • • • • • Location: soil, rocks, tree bark Help form soil Colonize rocky sites that were previously colonized by lichens Prevent soil erosion – Grow packed together in dense colonies The Moss Body – Thallus – Body structure – Rhizoids – hair-like absorptive structures • Do not have true roots, stems, or leaves Many mosses have separate sexes: male plants and female plants The gametophyte generation is dominant

Lifecycle of Mosses: Read p. 435

A filament of haploid cells that grows from a spore

Bryophytes

Gametophyte Generation Sporophyte Generation

Liverworts

• • Thallus – A body that lacks roots, stems, or leaves – Liverworts get their name from their liver shaped thallus Gemmae – Asexual reproductive structure of liverworts – Small balls of tissue – Borne in a saucer-shaped structure – gemmae cup

Hornworts

– Location: fields & roadsides – Thalloids - 1-2 cm – Sporophyte generations form hornlike projections out of the gametophyte thallus

Hornworts