Plant Biology: Bryophytes and Ferns
Introduction to Plants
Plants and green algae share a number of characteristics:
- Plants and green algae both have chlorophylls a and b
- Plants and green algae both store starch for food reserves
- Plants and green algae both have cellulose in their cell walls
When plants became established on land they had a number of characteristics that helped their survival:
- Plant surfaces have waxy cuticle to prevent water loss
- Gametangia and sporangia became multicellular
- Zygotes developed into multicellular embryos
Bryophytes
}}No bryophytes have true xylem or phloem, and they do not have roots}}
Most bryophytes absorb water through their surfaces
Water is incredible important to bryophytes, as it is needed for sexual reproduction. This is why bogs are such great habitats for them.
Bryophytes are pioneer species that colonize bare rock, accumulate minerals and organic matter used by other organisms, and retain moisture, reducing flooding and erosion.
Alteration of Generations
In mosses the leafy plant is a major part of the gametophyte generation
The sporophyte generation grows from gametophytes
The protonema in a bryophyte is an immature gametophyte consisting of short filaments
Phylum Bryophyta
Phylum Bryophya contains peat mosses and true mosses
Peat moss leaves have large transparent cells without chloroplasts that absorb water as well as small, green photosynthetic cells sandwiched between.
Mosses primarily asexually reproduce through fragmentation, when part of a moss is moved from it’s original location.
Peat mosses are the most important bryophyte for humans, as they are used in soil to absorb excess water and they store carbon.
Seedless Vascular Plants
During the early stages of vascular plant evolution internal conducting tissues developed, true leaves appeared, roots that function in both anchorage and absorption developed, and gametophytes became progressively smaller.
Seedless vascular plants include whisk ferns, club mosses and quillworts, horsetails and scouring rushes, and ferns.
Phylum Polypodiophyta: The Ferns
Fern leaves are referred to as fronds.
In ferns, the sporophyte is the conspicuous phase.
Fronds first appear coiled in a fiddlehead before unrolling and expanding.
Spores occur in clusters on the underside of fronds known as sori.
In ferns, spores are released and grow into gametophytes called prothalli.
Prothalli are one cell thick and have archegonia and antheridia.
In ferns when zygotes develop into young sporophytes, the gametophyte (or a portion of it) dies, leaving the sporophyte growing independently.