Mosses Flashcards
What is a plant
Autotrophs (make their own food) or derived heterotrophs
Alternation of generations between haploid and diploid
Protected embryo
Cell division - phragmoplast and cell plate
Chlorophylls a and b
Cellulose and starch
Alternation of generations
Feature of life cycle of plants
The dominant generation differs in different plant groups
The subordinate generation may be very tiny
male gametophyte (n) and a female gametophyte (n) produce gametes (sperm and eggs, respectively), which combine in fertilization to form a diploid plant called a sporophyte (2n). This sporophyte will grow and then produce spores, through meiosis, that will germinate into a new gametophyte (n), thus the alternating cycle is complete
Byrophytes
Autotrophic non-vascular plants with protected embryos and gamete production
Mosses, liverworts and hornworts
Share a lifestyle but may be unrelated
Number of byrophyte species
15000-20000
Challenges of life on land
Support
Transport of gametes
Desiccation vs gas exchange
Acquiring nutrients
Importance of byrophytes
Peat- globally important carbon store
Water and nutrient retention in major ecosystems
Habitat for invertebrates
Biodiversity
Hugely sensitive to environmental change
Which ecosystems do bryophytes dominate
UK western woodlands
Cloud forests
Tundra
Bryophyte phyla
Hepatophyta (liverworts) 6,000 species
Anthocerophyta (hornworts) 100 species
Bryophyta (mosses) 9,500 –12,500 species
Basic body plan of hornworts
Thalloid only
Thallus
Undifferentiated flat structure
Basic body plan of liverworts
Thalloid or ‘leafy’
Basic body plan of mosses
Always ‘leafy’
Shared lifestyle features
Alternation of generations with haploid gametophyte dominant
Sporophyte completely dependent on gametophyte
Gametes transported in wet environment
Cuticle absent from gametophyte – generally absorb (nutrients, water, pollutants) over all surfaces
No true vascular tissue (xylem and phloem absent)
No roots. Rhizoids in mosses (multicellular) and liverworts (unicellular)
No lignin - cannot grow tall
Archegonia
Eggs are produced in archegonia
Antheridia
Sperm are produced in antheridia
Spore dispersal
Spores are dispersed from capsules
-moist capsule
-drying capsule
-dried capsule
Limitations of the bryophytes
Need free water- for reproduction
Vulnerable gametophyte - no cuticle so can desiccate
Limited by internal transport systems- slow growth
Limited rigidity
Bryophytes vs vascular plants
Bryophytes:
Primitive conducting tissue
Simple unbranched dependent sporophytes
No lignin
Vascular plants:
Efficient conducting tissue – xylem and phloem
Branched and independent sporophytes
Lignin provides rigidity (woody tissues)
2 forms of mosses
Acrocarpous - cushiony or upright mosses)
Pleurocarpous - feather mosses
Moss life cycle
Female gametophyte (n)- leafy green part of moss- archegonia
Male gametophyte (n)- antheridia
Raindrop splashes the sperm to the egg/ sperm swims to egg in wet
Fertilisation to form zygote (2n)
Embryo
Young sporophyte (2n) grows out of gametophyte
Capsule inside sporophyte
Meiosis —> spores (n) form - beginning of gametophyte generation
Why can’t mosses grow tall
No lignin
Dominant generation
Gametophyte
