moss & fern notes b1

Mosses & Ferns

Kingdom Plantae 
All Materials © Cmassengale   

Seedless Nonvascular Plants

  • Includes mosses, liverworts, and hornworts
  • Lack vascular tissue (xylem & phloem) to carry water & food
  • Have a Sporophyte & Gametophyte stage known as alternation of generations
  • Gametophyte is dominant stage
  • Reproduce by spores

Division  Bryophyta

 Mosses:

  • Small, nonvascular land plants
  • No true roots, stems, or leaves
  • Class Musci
  • Most common bryophyte
  • Grow on moist areas (brick walls, as thick mats on forest floors, and on the shaded side of trees)
  • Some can survive periodic dry spells & revive when H2O becomes available
  • Must grow close together and must have H2O to complete their life cycle 
  • Sperm swims to egg through drops of water during fertilization
  • H2O moves cell-to-cell by osmosis
  • Sphagnum moss is known for its moisture holding capacity, absorbing up to 20 times its dry weight with water.


MOSS SPOROPHYTES & GAMETOPHYTES

LIFE CYCLE OF MOSSES:

  • Mosses alternate between a haploid (n) gametophyte stage & a diploid (2n) sporophyte stage 
  • Gametophyte is the dominant generation

Moss Gametophyte

Moss Sporophyte

Polytrichum formosum with moss flowers

Tortula muralis?

  • Called alternation of generations

  • The haploid gametophyte stage contains half the chromosome number & produces gametes (egg & sperm) 
  • Gametophyte stage is dominant in the moss’s life cycle
  • Gametophytes are photosynthetic & have root-like rhizoids
  • The diploid sporophyte has a complete set of chromosomes & produces spores by meiosis
  • Sporophyte of a moss is smaller than, & attached to the Gametophyte
  • Sporophytes lack chlorophyll & depend on the photosynthetic gametophyte for food
  • Sporophyte has a long, slender stalk topped with a capsule
  • Capsule forms haploid (n) spores 


Moss Capsules

Sexual Reproduction in Moss:

  • Mosses produce 2 kinds of gametes (egg & sperm)
  • Gametes of Bryophytes are surrounded by a jacket of sterile cells that keep the cells from drying out
  • Female gametes or eggs are larger with more cytoplasm & are immobile
  • Flagellated sperm must swim to the egg through water droplets for fertilization
  • Moss gametes form in separate reproductive structures on the Gametophyte — Archegonium & Antheridium

Archegonium

Antheridium

moss archegonial head X 40.jpg (102370 bytes)

Mnium antheridial head 40X.jpg (660893 bytes)

  • Each Archegonium forms one egg, but each Antheridium forms many sperm
  • Fertilization can occur only after rain when the Gametophyte is covered with water
  • Sperms swim to the egg by following a chemical trail released by the egg 
  • A zygote (fertilized egg) forms that undergoes mitosis and becomes a Sporophyte
  • Cells inside mature Sporophyte capsule undergoes meiosis and form haploid spores
  • Haploid spores germinate into juvenile plants called protonema
  • Protonema begin the Gametophyte generation

Protonema of Funaria hygrometrica
Protonema

  • Spores are carried by wind & sprout on moist soil forming a new Gametophyte

Asexual reproduction in Mosses:

  • Asexual reproduction in moss may occur by fragmentation or gemmae
  • Pieces of a Gametophyte can break off & form new moss plants (fragmentation)
  • Gemmae are tiny, cup shaped structures on the Gametophytes 
  • Raindrops separate gemmae from the parent plant so they can spread & form new Gametophytes 

Gemmae cups

Uses for Moss:

  • Help decomposer dead logs
  • Serve as pioneer plants on bare rock or ground
  • Help prevent erosion
  • Provide shelter for insects & small animals
  • Used as nesting materials by birds & mammals
  • Sphagnum or peat moss forms peat bogs (wet ecosystem)
  • Peat is burned as fuel in some areas

Division  Hepatophyta  

Liverworts:

  • Nonvascular
  • Undergo alternation of generations with Sporophyte attached to Gametophyte
  • Gametophytes are green & leafy and the dominant generation


Liverwort

  • Need abundant water for fertilization
  • Reproduce by spores
  • Grow on moist rocks or soil
  • Reproduce asexually by gemmae and by growing new branches

Division  Anthocerophyta

Hornworts:

  • Small, nonvascular bryophytes
  • Gametophyte leafy like liverworts
  • Archegonia & antheridia form inside the plant
  • After fertilization, zygotes develop into long, horn-shaped Sporophytes
  • Horn-shaped Sporophytes capable of photosynthesis so not completely dependent on Gametophyte


Hornwort

Seedless Vascular Plants

  • Includes club mosses, whisk ferns, horsetails, & ferns
  • Have specialized vascular tissues (xylem & phloem) to transport H2O, food, etc.
  • Have a Sporophyte & Gametophyte stage known as alternation of generations
  • Sporophyte is the dominant stage
  • Reproduce by spores

Division  Psilophyta

Whisk Ferns:

  • Photosynthetic, aerial stem forks repeatedly to form a small twiggy bush
  • No true roots, stems, or leaves
  • Have horizontal, underground stems called rhizomes
  • Root-like structures called rhizoids anchor plant
  • Reproduce by spores & vegetatively from rhizomes
  • Only 2 living genera


Whisk Fern

Division  Lycophyta

Club Mosses:

  • Low growing plants resembling pine trees
  • Have a club-shaped spore producing structure


Club Moss

  • Some like Lycopodium contain chemicals that burn quickly
  • Resurrection moss is green (after rains) when moist and brown when dry.

Resurrection Plant

resurrection plant

Division  Sphenophyta

Horsetails:

  • Equisetum called scouring rush is the only living species
  • Photosynthetic aerial stems & underground rhizomes
  • Stems contain silica & were once used to scrub pots
  • Reproduce by means of spores made in small cones at the tip of branches
  • In prehistoric times, some plants of this family grew to be large trees
  • Found in wetlands


Horsetail

Division  Pterophyta

Ferns:

  • Largest group of living seedless vascular plants
  • Live in moist habitats
  • Alternates between dominant Sporophyte stage & Gametophyte stage
  • Sporophyte stage has true roots, stems, & leaves
  • Produce spores on the underside of leaves 

fern sporangia.jpg (47544 bytes)

  • Leaves are called fronds & are attached by a stem-like petiole


FERNS

Fern Life Cycle:

  • Spores produced on underside of fronds in clusters of sporangia called sori
  • Spores undergo meiosis, are spread by wind, & germinate on moist soil to form prothallus
  • Prothallus begins the Gametophyte stage
  • Mature Gametophytes are small, heart-shaped structures that live only a short time
  • Male antheridia & female archegonia grow on the prothalli
  • Sperm must swim to the egg to fertilize it & developing embryo becomes the Sporophyte generation
  • Newly forming fronds are called fiddleheads & uncurl

Uses for Ferns:

  • Prevent erosion
  • Fiddleheads serve as food
  • Ornamental plants
  • Formed coal million of years ago