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Applied Biology (Wk 7) - Lecture 1 = Ch 29 (Land plants evolves from green…
Applied Biology (Wk 7) - Lecture 1 = Ch 29
Land plants evolves from green algae
Plants supply oxygen and ultimately most of the food eaten by terrestrial
Green algae charphytes are the closest relative to plants
Plants are multi-cellular, phototsynthetic autotrophs
Plants have cell walls are made of cellulose
chloroplasts with chlorophyll a and b are present
Charophytes are the only present-day algae that share key traits with land plants
Rings of cellulose-synthesising proteins
These synthesis the cellulose microfibrils fot eh cell wall
Structure of flagellated sperm
The structure resembles sperm of chrophytes
Formation of phragmoplast
Collection of centrally located microtubules that form during th later stages of cell division
Mosses and other nonvascular plants have life cycles dominated by gametophytes
Three phyla
Hepatophyta (HORNWORMS)
Have stomata
cells with single large chloroplast
Often form symbitoic relationship with cynobacteria
Sporophyte growths resembling small "horns"
Anthocerophyta (LIVERWORMS)
Grow nearly flat along ground
some only some have stomata
others exchange gas through thin cuticle
Gametes swim in a film of water along the surface of the cells, and their sporophytes are microscopic
Bryophyta (MOSSES)
produce flagellated sperm
form ground hugging carpets
only a few cells thick
may grow vertically
anchored by delicate rhizoids which a tubular cells are filaments of cells
Height of gamete
Sporophytes
smallest and simplest of all extant plant group
single moss capsule can produce 50 million spores
the peristome regulate spore dispersal
have stomata
Many species can increase the number of individuals
Non vascular plants
lack specialises tissues for transporting water and nutrients
embryos develop inside specialised tissue to avoid desiccation
Thin cuticle to reduce water loss
apical meristems direct growth to light and water
Ferns and other seedless vascular plants were the first plants to grow tall
Vascular plants
life cycles with dominant sporophytes
vascular tissues called xylem and phloem
well-developed roots and leaves
Key Adaptions
Vascular tissues
Roots
organs that anchor plants
Enable the absorption of water and nutrients from the soiul
Leaves
increase SA
Microphylls and Megaphylls
At each node a leaf trace diverges leaving a small segment of the vascular cylinder as just parenchyma
Sporophylls
Modified leaves with sporangia
Vary greatly in structure
produce clusters of spores called sori
Vascular tissues
Phloem
distributes sugars, amino aids and other products
consists of living cells
Xylem
conducts water and minerals
includes dead cells
Seedless Plants
Lycophyta
each leaf is narrow, unbranched midvein
Monilophyta
Leaves generally have branched venation
Monilophytes
Lycophytes
Fir mosses
Spike mosses
Tree fern
Bracken fern
Whisk ferns
Significance
exploit direr areas
grow taller to compete for light
expulsion of plant biomass
Adaptions enabling the move to land
in charophytes, a sporopollenin prevents exposed zygotes from drying out
movement into lnad provided unfiltered sun
land presented challenges: scarcity of water and lack of support
Land plants
Alteration of generations and multi cellular, dependent embryos
alternate between two multi-cellular stages called alternation of geneerations
the embryo is retained within the tissue fo the female gameotophyte
nutrietnts transferred through placental transfer cells
Land plants are called embryophytes because of the dependency of the embryo on the parent
Walled spores produced in sporangia
Sporophyte produces spores in organs called sporangia
Diploid cells called sporocytes undergo meiosis to generate haploid spores
Spore walls contain sporopollenin, which makes them resistant to harsh environments
multicellular gametangia
Gametes are produced within organs called gametangia
female = archegonia (produces eggs and are site of fertilisation)
Male = antheridia, produce and release sperm
apical meristems
Plants sustain growth in their apical meristems
differentitate into diffferent tissue
Cuticle = waxy cover of the epidermis
Mycorrhizae = symbiotic associations between fungi and land plants
