Transcript seed - morescience

Tutorial: Plants
Kingdom: Plants
Domain Eukarya
Domain
Bacteria
Domain
Archaea
Common ancestor
Domain
Eukarya
The first plants
 For more than 3 billion years, Earth’s terrestrial surface was lifeless
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life evolved in the seas
1st photosynthetic plant organisms were aquatic green algae
(charophytes/chlorophytes)
 special adaptations for life on dry land
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protection from drying = desiccation
 waxy cuticle
gas & water vapor exchange (through cuticle)
 stomates
water & nutrient conducting systems
 xylem & phloem
protection for embryo
 seeds
Plant Diversity
Bryophytes
non-vascular
land plants
Pteridophytes
seedless
vascular plants
mosses
ferns
seedless plants
non-vascular plants
colonization of land
Gymnosperm
pollen &
“naked” seeds
conifers
Angiosperm
flowers & fruit
flowering plants
seed plants
vascular plants
Plant Classification
Bryophytes
Pteridophytes
Tracheophytes
Gymnosperm
Conifer
Angiosperm
Non-vascular
Vascular
Vascular
Vascular
seedless
seedless
seeds
seeds
Spores &
Haploid Gameotophyte
Spores &
Haploid Gameotophyte
Cones - naked seeds
Flowers - fruit w/ seeds
Swimming sperm
Swimming sperm
Pollen & Seeds
Pollen & Seeds
Mosses, liverworts
Ferns
Pine, Spruce, Redwood
Lily, Maple, Oak, Rose
Vascular tissue
 Transports materials in roots, stems & leaves
 Xylem
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carry water & minerals up
from roots
tube-shaped dead cells
 only their walls provide a system
of microscopic water pipes
 Phloem
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carry nutrients throughout plant
 sugars (sucrose), amino acids…
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tube-shaped living cells
Flower
 Modified shoot with 4 rings
of modified leaves
sepals Stamen
 petals
 stamens

Stigma
Style
Ovary
Anther
Carpel
Filament
 male

carpel
 female
sepals
petals
stamens
Petal
Ovule
Sepal
carpel
Preventing self-pollination
 Various mechanisms
 stamens & carpels may mature at different times
 arranged so that animal pollinator won’t transfer pollen
from anthers to stigma of same flower
 biochemical self-incompatibility = block pollen tube growth
Fertilization in flowering plants
Double fertilization
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2 sperm from pollen
 2nd sperm fertilizes egg =
diploid zygote (n+n = 2n)
 1st sperm fuses with
2 polar nuclei to form
endosperm (n+2n = 3n)
 endosperm = food tissue in
seed
Polar
nuclei
Pollen
grains
Egg
cell
Seed & Plant embryo
 Seed offers…
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protection for embryo
stored nutrients for
growth of embryo
Embyonic leaves,
shoot, and root
endosperm = “food” storage
for developing plant until it
can begin making its own.
cotyledons = “seed” leaves,
first leaves of new plant
seed coat
endosperm
cotyledons
embryo
epicotyl
radicle
Co-evolution: flowers & pollinators
How a bee sees a
flower…insects see UV
light = a bulls-eye to the
nectar
Root Structure
Epidermis: skin covering
Root Hairs: extend out from the root
Root Cap - at the tip of the root,
produces a slimy substance
Phloem
Vascularization:
1. Phloem - food to the floor
2. Xylem - water up
Xylem
Rise of water in a tree by bulk flow
 Transpiration pull
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adhesion & cohesion
 H bonding
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brings water &
minerals to shoot
 Water potential

high in soil 
low in leaves
 Root pressure push
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due to flow of H2O
from soil to root cells
upward push of
xylem sap
Plant Responses
Tropism - growth in response to a stimulus
1. Phototropism • change in plant growth caused by light
(plants bend toward light)
2. Photoperiodism• developmental responses of
plants to the relative lengths of
light and dark periods.
3. Gravitropism • change in plant growth in response to the direction
of gravity (plants bend up, away from gravity)
4. Thigmotropism • growth in response to touch or contact
(plants bend along or around objects)
Plant Responses - Seasonal changes in leaves
1. Evergreen - they gradually shed some of their leaves
throughout the year, and as a result, maintain leaves year-round.
What classification of plants are they?
In what biome would you find them?
2. Deciduous - lose all their leaves at once, usually for winter.
As chlorophyll productiveness declines with the cool temperatures of autumn, the
dominant green color fades, displaying the yellows, oranges, and reds of the accessory
pigments.
Colors of the rainbow:
ROYGBIV
accessory pigments: xanthraphyll (yellow) and carotenoids (reds and oranges)
cannot transfer light energy directly to the photosynthetic pathway, they must pass their
absorbed energy to chlorophyll. If chlorophyll is rendered ineffective, the energy does not
get passed on, therefore, food is not being made, and consequently the leaves will die.
Abscission - shedding of leaves, fruits, flowers
Senscence - dieing off of the plant or plant parts