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