Transcript Parts of a Plant – Leaves, Roots, Stems and Tissues

Parts of a Plant – Leaves,
Roots, Stems and Tissues
Function of
Leaves
1. Main photosynthetic organ
2. Broad, flat surface increases
surface area for light
absorption
3. Have systems to prevent
water loss
•
•
Stomata open in day but
close at night or when hot to
conserve water
Waxy cuticle on surface
4. System of gas exchange
•
Allow CO2 in and O2 out of
leaf
Elephant Ear Plant
Leaf Structure: Overview
• Epidermis is a waxy
cuticle layer to prevent
water loss
• Mesophyll (palisade and
spongy) takes up most of
the leaf layer
– Most of chlorophyll for
photosynthesis is found
here
• Moist air spaces allow
for gas exchange
• Vein carry water,
nutrients and gases
Leaf Structure: Stoma and Guard
Cells
• Stoma is a small opening
(pore) in the leaf
– Open: O2 goes out, CO2
comes in (or water comes
in/out)
– Closed: No gas exchange (or
water stays inside the leaf)
• Guard cells – pair controls
the opening and closing of
stoma
• Stoma will be open when
climate is moist (water is
available). When climate is
dry and water is scarce,
stoma will close as to
Pea leaf stomata
•
Leaf
Adaptations
Cacti
live in dry climates.
Leaves would be futile (water
loss = death of plant). It has
been modified into a spine to
prevent water loss
• Conifers have thin, short
waxy needles instead of
leaves. Windy, cold and dry
climates would kill the plant.
The needles keeps the water
in.
• Shade plants have more
chlorophyll, are thicker, wider
and greener. It helps them
photosynthesize in low light
• Sun-loving plants
photosynthesize in high light,
so thinner leaves help them
with this.
Photosynthesis
• Process by which plants convert carbon dioxide,
sunlight and water to oxygen, sugar and energy
– Occurs in chloroplasts of plant cells
– Chlorophyll pigment in thylakoid of chloroplast absorbs
the light energy to start process
Function of Roots
1. Anchor & support plant in
ground
2. Absorb water and minerals
3. Hold soil in place
Taproots have large main root
with shorter branches. Fibrous
roots is a network of similarly
sized
smaller
roots Some
(no main
Roots
do have
adaptations.
of which are:
root)
•Grow
above-ground to collect more water
•Aerial plants can grow downwards on top of
standing plants, killing them. This allows the aerial
plant to obtain the food, water and light they
need for survival.
Root Growth
1. Root Hairs (collect water
and nutrients)
2. Zone of Maturation
(where root cells become
mature)
3. Zone of Elongation
(lengthening of root cells)
4. Zone of Cell Division
(includes Apical
Meristem, which
generates new cells)
5. Root cap (protective cap)
Function of
Stems
1. Support system for plant body
– Woody plant stems are hard to bend whereas
most flowering plants are softer
2. Transport system carries water & nutrients
(through vascular tissue!)
3. Holds leaves & branches upright
Stem Growth of
Woody Plant:
Looking at the
picture below:
What years had
the most rain?
What years
experienced the
worst drought?
Stem Adaptations and Uses
Stem Adaptations
• Cacti plants have large
stems to hold water
• Some plants have parts
of them stem
underground that shoot
off to form new plants =
reproduction
Practical Uses:
• Woody plants for wood,
paper, fuel, etc
• Maple syrup, root beer,
ginger & ginger ale,
gum (from Chicle tree)
• Dyes, resins, gums and
tannins
Vascular
Tissues
• Instead of arteries,
veins and capillaries,
plants have two
types of vascular
tissue in stems:
– Xylem  thickcelled & dead;
transports water
and dissolved
minerals
– Phloem  thincelled & living;
transports sugars
and nutrients
through stem
• Cambium  layers
of cells between
xylem and phloem
Filler
& protective
cells
that are
able
to
divide
phloem
cambium
xylem
Vascular Cambium
• Vascular cambium forms a
continuous cylindrical layer
inside the stem that can
reproduce
• Vascular cambium cells
divide to form new xylem
cells towards the inside of
the stem and new phloem
toward the outside of the
stem
• Form tree rings (wood
consists entirely of xylem)
• Heartwood: Supports the
tree (no transport)
• Sapwood: Conducts water
and nutrients
• Cork: protects the tree
• Phloem: transports sugar
and nutrients