Kingdom PlantaeKingdom Plantae

Phylum BryophytaPhylum Tracheophyta

Jaime Crosby, CHS

Phylum BryophytaPhylum Tracheophyta

Jaime Crosby, CHS

The first plants were water plants (algae)

• Adaptations necessary for life on land– The ability to acquire water– The ability to conserve water– The ability to transport water– The ability to reproduce without water

The first land plants…

• Fossils didn’t tell us much as they had soft bodies, so they didn’t preserve well

• 500 to 600 mya– Phylum Bryophyta: Mosses,

liverworts and hornworts– Phylum Tracheophyta: Ferns and

higher plants

Difficult Adaptations to land

• Requirements for life on land:– All cells need a constant supply of

water, especially those exposed to dry air like stems

– All plants must prevent water from escaping once it is obtained

– Food making parts must have a support system that exposes them to the sunlight

– Plants must be able to transport water up and food down the stem

– Exchange water and CO2 without dessication

– Reproduction in an environment that lacks standing water for the sperm to swim, and to prevent embryo from drying out

Have bryophytes adapted?

• PARTIALLY! They live on land, but still need to remain moist.

• Tracheophytes continued to evolve

Mosses, Liverworts and Hornworts

• Exhibit alternation of generations between haploid gametophyte and diploid sporophyte stages

• Gametophyte: dominant in mosses—the stage we SEE

• Sporophyte: dependant diploid phase

• Grow in swamps, near streams in rainforests and in other moist areas

• Perform photosynthesis (green)• Only grow a few cm tall because

they don’t have xylem and phloem!– Non-vascular

Structure of Bryophytes

• Rhizoids (not roots!) branch into the ground to anchor plants

• Mature gametophyte stage makes small umbrellas which release eggs and sperm

• Liverworts: flat green leaves

• Hornworts: flat green leaves with a sporophyte generation that looks like a tiny french horn

Differences from other, more advanced plants—this is what limits Bryophytes

• Lack vascular tissue– Water passes from cell to cell by osmosis…

thus mosses are short• Lack cuticle

– Lose water very quickly• Lack true roots

– Inefficient absorption and transport of water– Rhizoids anchor but do not absorb

• Have sperm cells with flagella that have to swim to fertilize eggs

For these reasons, bryophytes must live in areas that are wet for at

least part of the year. They can live in dry areas, but

cannot grow while they are dry.

Alternation of Generations in mosses

• Life Cycle: KNOW THIS!– Gametophyte stage

• Antheridium-male reproductive structure; produces sperm cells

• Archaegonium-female reproductive structure;produces egg cells

• Both are designed to avoid dessication

Alternation of Generations

• Sporophyte stage– A diploid capsule that emerges above

moss plant (foot + stalk + capsule)– Inside, haploid spores are produced– Capsule opens, spores carried away– Spore lands in wet area, grows into

PROTENEMA, which grows rhizoids and becomes the moss

Summary of Life Cycle

• Haploid gametophyte is dominant, obvious stage

• Diploid sporophyte is DEPENDENT, because it requires energy from the gametophyte to occur

• Some mosses are hermaphrodites, self or cross-fert.

• Water must be present for sperm to swim and syngamy to occur