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 Structure and Function LEAVES

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.

19. Water Transport – Transpiration

20. Water Transport – Transpiration

22. Gas (Air) Exchange – CO2 and O2

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