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Plants make up over 50% of the living
organisms on this planet
They belong to the kingdom Plantae
There are five phylum:
 Bryophyta
 Filicinophyta
 Coniferophyta
 Angiospermophyta
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Angiosperms are the most dominant phylum
Angiosperms, or flowering plants, produce
seeds enclosed inside fruits.
Angiosperm comes from the word
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angerion – a container
sperma – a seed
phyton – a plant.
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Angiosperms are divided into two large
groups:
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Monocotyledons (Monocots)
Dicotyledons (Dicots)
These names refer to the number of leaves
contained in the embryo, called cotyledons.
APICAL MERISTEMS
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Primary growth
Allows plant to grow
longer (upwards)
Forms leaves and
branches
Increases photosynthetic
capacity
Found in both monocots
and dicots
LATERAL MERISTEMS
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Secondary Growth
Allows plant to grow in
width
Widening of main trunk
for support and
depositing of vascular
tissue and bark
Found only in dicots
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Supports the leaves for photosynthesis
Transports water and nutrients from roots to
leaves
Support is achieved by:
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Tugor
Cellulose walls
Lignin reinforcing the xylem
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Consist of an epidermis which surrounds the
vascular tissue, composed of xylem (water
transport, up the stem) and phloem (mineral
and sugar transport, up and down the stem to
sinks for storage)
Meristems deposit secondary xylem and
phloem, which will grow outwards to become
primary xylem and phloem.
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Consists of a:
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Leaf Blade
Leaf stalk
Leaves have a large surface area and a small space
between layers
Designed for photosynthesis
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Leaves consist of:
Outer structure - Epidermis
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Tough, transparent layer
 Upper – waxy Cuticle
 Lower – specialized cells called guard cells, that form
openings in the bottom, called Stoma
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Inner Structure – Specialized Cells
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Mesophyll cells
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Upper Surface – Palisade Mesophyll
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Lower Surface – Spongy Mesophyll
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Tightly packed
Contain chloroplasts
Loosely packed with air spaces
Vascular Bundles
Consist of xylem and phloem
 Bring water to and transport sugars and minerals
away and to leaves
 Support the leaves along with cellulose and turgor
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First stage of development for the seed when it
germinates
Tap Roots
Lateral Roots
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Roles
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Absorption
Anchors
Support
Storage
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Roots have an outer coat, called the epidermis,
and the inner portion is called the cortex
In the root, there is a vascular bundle, of xylem
and phloem
Branching of roots allow for a greater surface
area
Root hairs off of growing roots, increase the
surface area as well.
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Roots
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Prop Roots
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Storage Roots
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Pneumatophores
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Buttress Roots
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Stems
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Bulbs
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Tubers
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Rhizomes
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Stolons
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Leaves
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Tendrils
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Reproductive Leaves
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Bracts or floral leaves
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Spines
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Plant growth is controlled by gravity and light
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Plant grows against gravity
Plants grow towards the light
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Responses to the above stimuli, called tropisms
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Growth towards light called phototropism
Controlled by a hormone called auxin
 Produced in the tip of the shoot
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Steps of phototropism
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Photoreceptors in the tip of the plant sense the light
Stimulate the production of auxin
Auxin will travel to the “shady side” of the plant, as
detected by the phototropins
Promotes the elongation of cells in stems, by
loosening the connections between the cell walls and
cellulose microfibrils
Promotes the stem to grow more on the shadier side
and go towards the light.
Allows the leaves on the sunny side to get more light
and photosynthesize at a greater rate.
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Root System
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Transpiration
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Water uptake
Factors affecting Transpiration
Translocation
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Roots – Absorption and uptake
Provide large surface area for uptake of water and
minerals
 Water is absorbed by osmosis
 Amount of water absorbed is increased by root hairs,
on ends of growing roots
 Minerals absorbed by active transport
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Occurs by osmosis
Flows through epidermis, into cortex by mass
flow, as the cells are interconnected
Three possible routes for uptake of water:
Apoplast Pathway (Mass Flow)
 Symplast Pathway
 Vacuolar Pathway
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Apoplast Pathway (Mass Flow)
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Most common way for water to move (faster)
Water does not enter the cell
Moves through the cell walls until it reached the
endodermis
Cells of the endodermis have a Casparian Strip
around them that is impermeable to water
The water is diverted to the spaces of dead cells,
eventually to the xylem
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Symplast Pathway
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Water enters the cytoplasm but not the vacuole
It passes from cell to cell via connections between
cellular cytoplasm of adjacent cells, called
plasmodesmata
The organelles are packed together in cells, and as a
result, block significant progress of water
It is not the major pathway for water. Minerals
mainly move through this pathway.
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Vacuolar Pathway
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Water enters the cell and move into the vacuole
It can be stored in the cells
It can also travel through the cytoplasm and the cell wall
to the next cell, to move into cortex
Once in the endodermis, water can move into
the xylem and pulled via transpiration forces.
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Minerals are important to build cells walls,
carbohydrate storage and protein synthesis
Processes for mineral uptake:
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Active transport
Mass flow (in water)
Fungal hyphae
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Transpiration
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the loss of water vapour from the leaves and stems
of plants.
Like perspiration
As water is lost, the amount of water in the
plant decreases. A pull is created in the plant
to “pull” water up the plant. This is similar to
maintaining homeostasis.
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Water moves from root to leaf by transpiration
pull
Water moves up the stem to leaves in the
xylem
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Dead material
Made of tracheids and xylem vessels
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Controlled by stomata
Stomata open and close depending on the
amount of water in the plant
If there is a lot of water – high turgor pressure
in guard cells and stomata are open
If there is a deficiency of water – low turgor
pressure in guard cells and stomata close
If water drops, abscisic acid is released,
overriding all variables and stomata close
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When stomata are open, water vapour is lost to
the external environment
Concentration gradient is created
The lost water needs to be replaced
Water moves from the high concentration
(roots) to lower concentration (leaves) and
moves up the plant
Cohesive forces of water allow water to move
in a continuous flow
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Biotic Factors
Size of the plant
 The thickness of the cuticle
 How widely spaced the stomata are
 Whether the stomata are open or closed
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Abiotic Factors
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Temperature
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Humidity
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Wind
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Light
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All of these can be over ridden by abscisic acid
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Movement of manufactured food (sugars and
amino acids).
Occurs in the phloem tissues of the vascular
bundles.
Moves sugars from source to sink (leaves to
storage) and from source to areas of new
growth, like ends of shoots and new leaves.
Phloem tissue allows movement up and down
the stem of the plant
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Phloem Tissue, is living tissue, and consists of:
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Sieve tubes
 Flow of sugars and minerals
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Companion cells
 Control flow / Active transport
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Theory of Translocation is by mass flow, from
source to sink
Source and sink can change, depending on use
and season
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Small, thick leaves
Reducing the number of stomata
Stomata located in crypts or pits
on the leaf surface
Thickened, waxy cuticle
Hair-like cells on the surface to
trap water vapour
Become dormant in the dry
months
Store water in the fleshy stems
and restore the water in the rainy
season
Using alternative photosynthetic
processes called CAM
photosynthesis (Crassulacean acid
metabolism) and C4
photosynthesis
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Parts of the flower
Pollination
Fertilization
Seed formation and
dispersal
Seed germination
Control of flowering Photoperiodism
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Sepal
 enclose and protect the flower in the bud, and are
small, green and leaf like.
Petals (together called the corolla)
 coloured and used to attract insects or other small
animals to pollinate the flower.
Stamen – male part of the flower, which consists of:
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Anthers – produces the male sex cells house the
pollen grains
Filament or stalk – holds up the anther
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Carpels – female part of the flower, and they
may be on their own or fused together. Each
carpel consists or:
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Ovary – at the base of the carpel which contains the
female sex cells (containing many ovules)
Stigma – sticky top of the carpel (to receive the
pollen)
Connecting style – supports the stigma
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Pollination
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the transfer of pollen from a mature anther to a
receptive stigma.
Fertilization
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occurs after the pollen grain has landed on a stigma,
and germinated there. It is the fusion of the male
and female gametes.
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Process of Fertilization
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The pollen produces a tube, which grows down
between the cells of the style, and through the ovule.
The pollen tube delivers two male nuclei.
 One of these male nuclei then fuses with the egg
nucleus in the embryo sac, forming a diploid zygote.
 The other fuses with the other nucleus, which triggers
formation of the food store for the developing embryo.
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Seed contains the developing embryo and the food
store
The zygote grows by mitosis, forming the embryonic
plant, consisting of an embryo root and stem.
A seed leaf or cotyledon forms. The seed leaf has two
forms, as angiosperms have two classes.
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Monocotyledons – have a single seed leaf
Dicotyledons – have two seed leaves
The formation of stored food reserves is triggered. In
many seeds the food store is absorbed into the
cotyledons.
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The outer layers of the ovule become the protective
seed coat, or testa.
The micropyle is a small hole through the testa,
where it was attached to the parent plant.
The whole ovary develops into the fruit.
The water content decreases and the seed moves
into a dormancy period, assisted by the formation
of abscisic acid.
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Seeds are dispersed when “fruit” ripens
Seeds are dispersed in such a way as to
eliminate many seeds in one place and around
the base of the parent plant (population
dynamics)
Dispersed by:
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Wind
Animals
Explosive
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Seeds are in suspended animation
When metabolic activity starts, this is
germination
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Seeds are dormant because:
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Incomplete seed development
 Presence of a plant growth regulator – abscisic acid
 Impervious seed coat
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In order for germination to occur, the proper
conditions are needed
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Water – hydrates plant and activates amylase and
removes the abscisic acid
Oxygen – for Cellular respiration
Period of warm temperatures as this is important
for enzyme production.
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The metabolic processes during the germination of a
seed are as follows:
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The seed absorbs water.
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Gibberellin, or gibberellic acid, is released after the uptake of
water and is a plant hormone
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Gibberellin triggers the production of amylase.
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Amylase causes the hydrolysis of starch into maltose. The
starch is present in the seed’s endosperm or food reserve.
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Maltose is then further hydrolysed into glucose that can be
used for cellular respiration or may be converted into cellulose
by condensation reactions.
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Cellulose is used to produce the cell walls of new cells.
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The seed coat cracks and out comes the plant.
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Photoperiodism
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Plant’s response to light involving the lengths of day and
night. It is the length of day and night that controls
flowers
Plants that respond to large amounts of sunlight,
and short periods of darkness are called long day
plants (late spring, summer)
Plants that respond to small amounts of sunlight,
and long periods of darkness are called short day
plants (early spring, late fall)
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It is actually the length of night that controls
the flowering process
The control by light is brought about by a
special blue-green pigment called
phytochrome.
Phytochrome is a large protein that is not a
plant growth hormone, but a photoreceptor
pigment.
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There are two forms of phytochrome:
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inactive form Pr
active form Pfr
In light, the Pr is converted to Pfr.
In darkness, the active form (Pfr) slowly converts
back to Pr
The slow conversion allows the plant to time the
dark period and controls the flowering in shortday and long-day plants.
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A long day in the summer:
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A lot of Pr is made into Pfr during the day.
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In the night, because the night is short, little Pfr is
converted back to Pr, and when the sun rises, there is
still a lot of active phytochrome (Pfr) left
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This signals a long day, short night, and promotes
flowering in long day plants
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This does not signal a short day, long night and
inhibits flowering in short day plants
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A short day in the spring or fall:
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A small amount of Pr is made into Pfr during the
day.
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In the night, because the night is long, almost all Pfr
is converted back to Pr, and when the sun rises, there
is minimal active phytochrome (Pfr) left and lots of
inactive (Pr)
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This does not signal a long day, short night, and
inhibits flowering in long day plants
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This does signal a short day, long night and
promotes flowering in short day plants
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Long day plants need active phytochrome (Pfr)
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Pfr acts as a promoter
Need a short night
Short day plants do not need active
phytochrome (Pfr)
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Pfr acts as an inhibitor
Need a long night