Download Root hairs

Why do we have more than cell making up our bodies?
Why don’t we have just one huge cell?
When a cell’s surface area to volume ratio is too small
(the surface area and volume are too close in number),
the efficiency of the cell’s functioning decreases.
An efficient cell has
the highest surface
area to volume ratio
possible! That’s from
the previous section.
So, if a cell gets too big, it’s surface area to volume ratio
goes down, decreasing its efficiency.
Each type of cell in a multicellular organism is an “expert”
at what it does. This is also called specialization.
(really is important!)
Internal transport systems in multicelluar organisms allows individual cells to
remain small and efficient.
If one or a few cells of a multicellular organism die,
then the organism can still go on living.
This is not the case for single-celled
organisms
Shoot System
Everything that is above ground:
• stem
• leaves
• fruits
• tubers
• buds
• flowers
Root System
Everything that is below ground.
Meristems are sites of rapid
cell division.
These areas are found at the ends
of growing roots and leaves.
root apical meristem
The epidermis is the very thin outer layer of cells that covers all parts of plants.
It’s main function is to facilitate gas exchange.
epidermis
stem cross section
leaf cross section
Dermal cells secrete a waxy cuticle that helps
protect the plant and prevent water loss.
cuticle
electron microscope view of the
cuticle on a cactus plant
cross section of the upper
surface of a leaf
The ground tissue is found just below the epidermis and makes up
the majority of the plant.
ground tissue
The cells are loosely packed to
allow gases to diffuse easily
around the cells.
In the stem of a plant, the ground
tissue provides strength and
support
stem cross section
The cells that make up the ground tissue (or cortex) in the root of a
plant are involved in food and water storage.
root cross section
ground tissue
In the leaf of a plant, the
ground tissue is the site
for photosynthesis.
Xylem tissue are the non-living cells responsible for transporting water and dissolved
minerals up the stem to the leaves for use in photosynthesis.
Phloem tissue transports the products of photosynthesis
(dissolved sugars) from the leaves to the rest of the plant.
root cross section
leaf cross section
vascular bundle
xylem
phloem
xylem
phloem
Cells in a vascular bundle seen through the light microscope (200X)
root hairs
Root hairs on a
developing bean plant
Cells of the root showing root hairs as
seen through the light microscope (100X)
Root hairs increase the surface area of the root to maximize the rate
of water absorption into the plant.
Frozen hydrated root hairs seen with a scanning electron microscope (SEM)
Stomata are tiny pores on
the underside of leaves that
facilitate gas exchange.
stoma
singular: stoma
plural: stomata
guard cells
Guard cells are specialized cells that surround each stoma
whose function is to regulated the size of the opening.
stomata
cuticle
upper epidermis
ground tissue
vascular tissue
xylem
phloem
stoma
lower epidermis
guard cells
 read pages 296 – 302
 C3.1 Check and Reflect
page 302 #’s 1 – 6
 Line Master 8