Transcript Cross-section of Leaf for cutout dayx

To Do: Thursday
1. Check your concept map with one
of the keys around the room
2. Go to one of the microscopes and
fill in your half sheet warm-up
3. Plant Book – Transpiration notes
4. Cross Section of a Leaf Cutout
Guard cells:
• cells that open and
close the stoma
Stomata: openings in
underside of leaf’s
surface; when open:
• GAS EXCHANGE:
Allows CO2 in & O2
out of leaf
• TRANSPIRATION:
Allows excess H2O
out of leaf
GUARD CELL WITH STOMATA
Cuticle
Guard Cells
Stomata (stoma)
Epidermis
Chloroplasts
Vascular bundle (vein)
1. Transpiration: loss
of excess water from plant
leaves
2. Significance:
a. Transpiration causes
enough pressure to help
pull water (& required
nutrients) up stem from
roots.
b. As part of the water cycle,
trees transpire water back
into the atmosphere.
c. Transpiration provides
much of the daily rain in
rainforest.
A average size maple tree can
transpire 200 liters of water
per hour during the summer.
Transpiration is the #1 driving
force for pulling water up
stems from roots.
•
•
The bulk of most leaves consist of a specialized ground tissue full
of chloroplasts known as mesophyll. The mesophyll contains two
layers:
1. Palisade Layer – Closely packed tall columnar cells; located
under the upper epidermis and absorbs light that enters the
leaf.
2. Spongy Layer – Loose tissue made of spherical cells that
contains many air spaces between its cells; the air spaces
connect with the exterior through the stomata (pore-like
openings that allow gases to enter and leave the leaf ).
The stomata and guard cells are also located on the leaf (already
discussed these structures previously).
A. Cuticle- outer waxy covering that
protects from water loss
B. Epidermis- outer tissue layer
C. Pallisade layer- contains the
majority of chloroplasts
D. Mesophyll- middle tissue layer
includes spongy & palisade
E. Spongy layer- contains chloroplasts
& exchange of gasses
F. Guard cells- control the opening
and closing of the stoma
G. Stomata- pores that allow gasses to
enter and leave the leaf
H. Vein- the vascular bundle, which
contains xylem and phloem.
vein
stomata
guard cell
Vein
stomata
Guard cells