Transcript 6 CO 2 + 6 H 2 O sunlight C 6 H 12 O 6 + 6 O 2

LEAVES AND THEIR MYSTERY
TO-QUY NGUYEN
http://whyleaves.tripod.com
OUTLINE
• 1. Function of leaves: Photosynthesis
• 2. Factors that influence color change in leaves
a. Leaf pigments
b. Length of night and day light
c. Temperature and Moisture
• 3. Mechanism of action
a. Molecular structures of pigments
b. Functions of the major plant pigments
• 4. Why do leaves fall?
• 5. What happens to fallen leaves chemically?
a. Decomposition
b. Food for soil organisms
• 6. Conclusion
FUNCTION OF LEAVES
• Photosynthesis:
6 CO2 + 6 H2O sunlight C6H12O6 + 6 O2
CHO
H
OH
HO
H
H
OH
H
OH
CH OH
2
D-GLUCOSE
http://www.sciencemadesimple.com/leaves.html
FUNCTION OF LEAVES
• Photosynthesis:
6 CO2 + 6 H2O sunlight C6H12O6 + 6 O2
- An Oxidation-Reduction reaction
- An Endothermic process
- Convert light energy into chemical
energy, which is used by plants for growth.
Salisbury, Frank. (1992). Plant Physiology. Wadsworth Publishing Company, Belmont.
FACTORS THAT INFLUENCE COLOR CHANGE
• Leaf pigments:
- Chlorophyll: green pigment.
- Carotenoid: yellow to orange pigment.
- Anthocyanin: red pigment.
• Length of night and day light: an important
signal for color changes.
When the day gets shorter, less sunlight is
available. Leaves begin to stop making food,
the chlorophyll breaks down and the green
color disappears. Yellow and red are shown.
Treshow, Michael. (1970). Environment & Plant Response.
McGraw-Hill Book Company: New York.
FACTORS THAT INFLUENCE COLOR CHANGE
• Temperature and Moisture:
- Warm, sunny days with cool nights: the most
brilliant colors are observed.
- Freezing or frost weather: dim colors
- Severe summer (drought): delay the process
of changing color
http://www.na.fs.fed.us/spfo/pubs/misc/leaves/leaves.htm
MECHANISM OF ACTION
• Chlorophyll:
- Green pigment
- Formula: C55H70MgN4O6
- Inside chloroplast, site
of photosynthesis.
- Not a very stable
compound
- Absorb Red and Blue
- Require light and warm
weather to be synthesized.
- Destroyed by low
temperature and bright
sunlight
http://scifun.chem.wisc.edu/chemweek/fallcolr/fallcolr.html
MECHANISM OF ACTION
• Carotenoids
– Carotene: orange
pigment.
– Lycopene and
Xanthophyll: yellow
pigment.
– Contain in the
chloroplasts
– A stable compound.
– Absorb blue-green and
green.
– Function as an
accessory absorber.
– Don’t require light in the
synthesizing process.
http://scifun.chem.wisc.edu/chemweek/fallcolr/fallcolr.html
MECHANISM OF ACTION
• Anthocyanins
– Red pigments
– A form of protection
– Not attached to cell
membranes.
– Absorb blue, blue-green,
and green.
– The appearance of colors
depend on the pH of the
cell sap.
– Formed by a reaction
between sugars and
certain protein in cell sap.
This reaction also
requires light.
http://chemistry.about.com/library/weekly/aa082602a.htm?si=471
WHY DO LEAVES FALL?
Sunlight
decreases
Veins that carry
sap close
Separation layer
Forms
Leaf is separated
and falls
http://www.dnr.state.wi.us/org/caer/ce/eek/veg/trees/treestruecolor.htm
FALLEN LEAVES
• Decomposition:
Decomposition
Fallen leaves
by Fungi & Bacteria
CO2
+
Nutrients
(K+& Na+)
• Make up part of spongy humus layer of forest floor
that absorbs and holds rainfall.
• Food for soil organisms
http://www.na.fs.fed.us/spfo/pubs/misc/leaves/leaves.htm
CONCLUSION
• Leave is truly a valuable natural resource.
• Similar to all of us, trees need sometimes
to relax after the long period of making
food, and autumn is the right time for
them to do so.
• It is really interesting to enjoy the palette
color of leaves, but it is even more
interesting to discover how and why they
have such wonderful colors.
REFERENCES
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The chemistry of autumn colors. Chemical of the week.
Retrieved March 15, 2005, from
http://scifun.chem.wisc.edu/chemweek/fallcolr/fallcolr.html
Why leaves change color. Retrieved March 15, 2005, from
http://www.na.fs.fed.us/spfo/pubs/misc/leaves/leaves.htm
Helmenstaine, Anne. Chemistry of autumn leaf color.
Retrieved March 10, 2005, from
http://chemistry.about.com/library/weekly/aa082602a.htm?si=4
71
Why do leaves change color? Retrieved March 29, 2005,
from
http://www.dnr.state.wi.us/org/caer/ce/eek/veg/trees/treestruec
olor.htm
Why do leaves change color in the fall? Retrieved March
29, 2005, from
http://www.sciencemadesimple.com/leaves.html
Treshow, Michael. (1970). Environment & Plant Response.
McGraw-Hill Book Company, New York.
Salisbury, Frank. (1992). Plant Physiology. Wadsworth
Publishing Company, Belmont.
THE END
ENJOY THE WONDERFUL PICTURE OF AUTUMN