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Transcript Vascular - Our eclass community
VASCULAR PLANTS:
STRUCTURE & FUNCTION
Keywords
Monocotyledons
(monocots)
Dicotyledons (dicots)
Taproots
Fibrous roots
Adventitious roots
Root hairs
Vascular bundles
Senescence
Abscission
Making connections
VASCULAR PLANTS
Plants
must capture and store sufficient
sunlight, water and minerals to survive.
To do so, they have specialised:
Root structures
Taproots
Fibrous roots
Leaf structures
Seed dispersal mechanisms
MONOCOTYLEDONS & DICOTYLEDONS
Vascular
plants are
classified into 2 types:
Monocotyledons
Dicotyledons
It
is suggested that
monocots ‘evolved’
first, since their
structures appear
less complex.
The creation model
would argue that God
made both unique
and that both
reproduce after their
own kind.
MONOCOTYLEDONS & DICOTYLEDONS
TAPROOTS
A
taproot system is characterized by having
one main root (the taproot) from which
smaller branch roots emerge.
When a seed germinates, the first root to
emerge is the radicle, or primary root. This
radicle develops into the taproot.
Taproots can be used for storage of
carbohydrates.
Example: sugar beet and carrot.
Taproots can grow extremely long in their
search for deep underground water sources.
Dicots mostly have taproot systems
TAPROOTS
Radicle with root hairs
FIBROUS ROOTS
A
fibrous root system is characterized by a
mass of similarly sized roots.
These roots spread out so that they can soak
up as much water as quickly as possible.
Adventitious roots may also be present.
Adventitious roots form on plant organs other
than the root.
Some fibrous roots are used as storage.
Example: sweet potato
Plants with fibrous roots systems are
excellent for erosion control, because the
mass of roots cling to soil particles.
Monocots mostly have fibrous root systems.
FIBROUS ROOTS
Fibrous
roots
Adventitious
roots
ROOT HAIRS
Both
taproots and fibrous roots have root hairs
that grow at the apex or tips of the roots.
Root hairs absorb water and nutrients from the
soil
STEMS
Monocot stems
Dicot stems
vascular bundles
cortex
pith
LEAF STRUCTURES
The
leaves of plants
are specialised in
many ways:
Size
Shape
Function
Leaves can be either
deciduous or
evergreen.
Monocot leaves have
parallel veins while
dicot leaves have a
network of veins
DECIDUOUS VS EVERGREEN LEAVES
Deciduous
leaves typically have a lifespan of
just one season, while evergreen leaves last
several seasons.
All leaves go through a process of senescence
or aging. In deciduous leaves, this may involve
a change in colour.
The plant recovers minerals and other chemicals
from the leaf during senescence.
This culminates in leaf abscission or the falling
off of the leaf.
The falling leaf often carries away toxins from
the plant.
Abscission is an important mechanism
equivalent to excretion.
LEAF STRUCTURE
The leaves of many plants limit water loss
through adaptation of size, sheen and/or
texture.
Small leaves or spines limit the amount of
surface area exposed to the drying heat.
Glossy leaves reflect the sun's radiant heat
reducing leaf temperatures and evaporation
rates.
Waxy leaves prevent moisture from
escaping. Water escapes from leaves
through the stomata, or leaf pores.
LEAF STRUCTURE
FLOWERS
Monocot
flowers have
flower parts in 3’s.
Dicot flowers have
flower parts in 4’s or 5’s
It is not always easy to
distinguish a monocot
from a dicot using their
flower parts because
sometimes flower parts
are fused or reduced
SEED DISPERSAL
Seed dispersal
mechanisms include:
by wind
by water
by explosive action
by humans & animals –
adhesion & food
DEFENSIVE MECHANISMS
Defensive
mechanisms are important
adaptations that help plants survive.
Defensive
mechanisms include:
sharp spines, thorns or hairs
cellulose - makes them hard to digest
chemicals - makes the plant toxic or smell
bad.
mimicry - helps the plant look like another
plant that is poisonous