Warm-Up #9 12/4/12
1) What are the 3 external plant layers?
2) Why are the top two layers clear?
3) What is the purpose of a stomata?
4) What controls the opening of stomata?
5) What layer are the stomata located?
Leaf Structure
Unit 5
Metabolism
Today is About…

Essential Question:

What happens when
leaves change color and
fall to the ground?

Objective

Diagram the structure
of a leaf
Photosynthesis

Occurs in the chloroplast of the leaves



Leaf is thin
Very large surface area (ideal for
diffusion/absorption). The larger the surface area
the more sunlight can be absorbed.
Mesophyll cells are closer to the surface \

reducing diffusion distance of CO2 from surrounding
mesophyll cells
External Features

Waxy Cuticle




Upper epidermal cells



Top of leaf
Transparent
Allows light to enter for
photosynthesis
Transparent
Allow light in to reach
the chloroplast
Lower epidermis

Has stomata, which
allows gas exchange
(intake of CO2 and
release of O2)
Stomata



Openings in the leaf
Controlled by doors called guard cells
Permit exchange of moisture and carbon
dioxide between leaf and atmosphere
Internal Features

Vascular Tissue- found in leaf vein

Xylem



Top of leaf
Transports water to leaf cells and then it diffuses into
chloroplast.
Phloem


Bottom of leaf
Transports food from mesophyll to rest of plant
Internal Features Cont.

Mesophyll- two main types

Palisade




Contain the most chloroplast
Found at top of leaf
Closely packed with small
spaces in between to allow
gas exchange
Spongy



Less chloroplast
Larger open spaces
Store carbohydrates made by
photosynthesis
Internal Features Cont.

Chloroplast




Contain chlorophyll (WHERE
PHOTOSYNTHESIS TAKES
PLACE)
Double membrane that is
selectively permeable
Allows H2O and CO2 to diffuse
into it and O2 to diffuse out
Parenchyma


Rich in chloroplast
Primary site of photosynthesis in
the leaf
http://academic.kellogg.edu/herbrandsonc/bio111/animations/0021.swf
Internal Features Cont…

Guard Cells

Controls the opening and
closing of the stomata
Warm- Up #8
12/3/12
2)
What part of the plant are most chloroplast found
in?
How is energy stored during photosynthesis
3)
How is energy released during photosynthesis?
4)
What is the product of the light dependent reaction?
5)
What is the product of the light independent
reaction?
1)