LEAVES AND THEIR MYSTERY

TO-QUY NGUYEN

http://whyleaves.tripod.com

OUTLINE• 1. Function of leaves: Photosynthesis

• 2. Factors that influence color change in leavesa. Leaf pigmentsb. Length of night and day lightc. Temperature and Moisture

• 3. Mechanism of actiona. Molecular structures of pigmentsb. Functions of the major plant pigments

• 4. Why do leaves fall?

• 5. What happens to fallen leaves chemically?a. Decompositionb. 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

CH2

OH

http://www.sciencemadesimple.com/leaves.htmlD-GLUCOSE

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

Separation layer Forms

Leaf is separatedand falls

Veins that carry sap close

http://www.dnr.state.wi.us/org/caer/ce/eek/veg/trees/treestruecolor.htm

FALLEN LEAVES

• Decomposition:

Decomposition +

by Fungi & Bacteria

• Make up part of spongy humus layer of forest floor that absorbs and holds rainfall.

• Food for soil organisms

Fallen leaves CO2Nutrients (K+& Na+)

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•

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=471

• Why do leaves change color? Retrieved March 29, 2005, from http://www.dnr.state.wi.us/org/caer/ce/eek/veg/trees/treestruecolor.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