Leaves, Structure and Function

Discussion of the functions of leaves, focusing on Photosynthesis and the process. Also covers transpiration, O2 CO2 transfer, germination. Appropriate for high school level students.

1. PLANTS PLANTS
Structure and FunctionStructure and Function

LEAVESLEAVES

2. Leaf Functions
•Manufacture food through photosynthesis
•Gas (Air) Exchange – Respiration
•Protect vegetative and floral buds
•Water Transport – Transpiration
•Store Food During Germination

4. Plants Manufacture Food Through
Photosynthesis
•3CO
2
+ 3H
2
O
light
C
6
H
6
O
3 +
3O
2
Stage 1:
Energy is captured from sunlight
Stage 2:
Light energy is converted to chemical energy
Stage 3:
Chemical energy powers formation of organic
compounds, using CO
2

5. What is Photosynthesis?
Photosynthesis is the process which
plants use the energy from sunlight
to produce sugar.

6. The conversion of unusable sunlight
energy into usable chemical energy,
is associated with the actions of the
green pigment chlorophyll.

7. Chlorophyll looks green because it absorbs red
and blue light, making these colors unavailable to
be seen by our eyes.
The green light which is NOT absorbed reaches
our eyes, making chlorophyll appear green.
It is the energy from the red and blue light that are
absorbed allowing the plant to do photosynthesis.
The green light we can see is not / cannot be
absorbed by the plant, and cannot be used for
photosynthesis.

8. Most of the time, photosynthesis
uses water and releases the oxygen
that we absolutely must have to stay
alive. And of course we need the
food as well!

9. The overall chemical reaction of this
process is:
6H2O + 6CO2 ----> C6H12O6+ 6O2
Translated it reads:
six molecules of water plus six
molecules of carbon dioxide
produce one molecule of sugar
plus six molecules of oxygen

11. Sugars produced by photosynthesis
are used directly in respiration.

12. Respiration is the release of the
energy derived from the food
created by photosynthesis.
It occurs all the time in all living
cells. There are 2 different kinds of
respiration:

13. Aerobic respiration:
Occurs only in the presence of oxygen.
It is the most common form of respiration.
Both plants and animals use aerobic respiration.
It is the opposite of photosynthesis (one molecule
of glucose and six molecules of oxygen are
broken up and reorganized by enzymes to give
six molecules of carbon dioxide
and six molecules of water.
Basically, this process makes
energy out of food

14. Anaerobic respiration:
occurs only under special
circumstances
occurs in the absence of oxygen
(for example: during the
fermentation process)

15. Usually, photosynthesis will produce
more glucose than is needed by the
plant.
The excess sugars are
stored and transformed
into starch, cellulose,
lipids (fats) and other
carbohydrates, proteins
and sucrose.

16. Other Functions of Leaves
•While
Photosynthesis
is a very
important part of
the function of
leaves, they
have other
responsibilities
to the plant

17. Leaves protect buds through the winter
Juniper
Mango
Protect Vegetative and Floral Buds
Leaves protect floral bracts during
development
Poinsettia
Globe artichoke

18. Important in the Water Cycle
•Leaves are a
very important
part of the
water cycle,
helping
provide
atmospheric
water.

19. Water Transport – Transpiration

20. Water Transport – Transpiration

21. Leaves Provide the Oxygen We
Breathe
•As part of Photosynthesis
leaves release Oxygen as a
by-product, or waste.
•Leaves use our by-product or
waste, Carbon Dioxide, for
photosynthesis
•This symbiotic relationship is
required for the continuity of
life

22. Gas (Air) Exchange – CO2 and O2

23. Leaves Store Food for the Future
•Germination (seeds
sprouting) requires
energy
•Leaves store energy
(glucose) as a result of
photosynthesis
•Seed leaves (cotyledons)
are enclosed in the seed
as food for the embryo
plant

24. Store Food During
Germination
Cotyledons (Seed Leaves)
Store Food While Seed
Germinates
Stores Food Until Plant Matures and
Begins Photosynthesis

25. Leaves – a Significant and
Important Structure of the Plant