1. LEAVES AND THEIR MYSTERY TO-QUY NGUYEN http://whyleaves.tripod.com

2. 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

3. FUNCTION OF LEAVES Photosynthesis: 6 CO 2 + 6 H 2 O sunlight C 6 H 12 O 6 + 6 O 2 CHO H OH CH 2 OH http://www.sciencemadesimple.com/leaves.html D-GLUCOSE

4. FUNCTION OF LEAVES Photosynthesis: 6 CO 2 + 6 H 2 O sunlight C 6 H 12 O 6 + 6 O 2 - 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.

5. 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.

6. 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

7. MECHANISM OF ACTION Chlorophyll: - Green pigment - Formula: C 55 H 70 MgN 4 O 6 - 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

8. 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

9. 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

10. WHY DO LEAVES FALL? Sunlight decreases Separation layer Forms Leaf is separated and falls Veins that carry sap close http://www.dnr.state.wi.us/org/caer/ce/eek/veg/trees/treestruecolor.htm

11. 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 CO 2 Nutrients (K + & Na + ) http://www.na.fs.fed.us/spfo/pubs/misc/leaves/leaves.htm

12. 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.

13. 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=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.

14. THE END ENJOY THE WONDERFUL PICTURE OF AUTUMN