1. How Plants Get Their Food

2. How do plants get their food ? 199.8 lb soil The soil was watered but nothing else was added. After 5 years, the tree had gained 169.2 lb in weight but the soil had lost only 2 pounds. van Helmont concluded that the tree had made 169lb of new growth from water alone. 2 200 lb soil In 1649, A Belgian physician, van Helmont, set up an experiment in which he planted a willow sapling, weighing 5 lb, in 200 lb of soil.

3. van Helmont’s experiment was effective in showing that the plant’s food did not come from the soil. But he had overlooked the fact that air was available to the plant as well as water. Could it be that the plant made 169 lb of material from just air and water? This might seem unlikely, but we now know that plants do indeed make their food using carbon dioxide from the air and water from the soil. 3

4. Feeding Animals get their food by eating plants, or other animals Carnivores eat animals Herbivores eat plants Plants make their own food They combine carbon dioxide from the air with water and dissolved salts from the soil Plants do NOT get their food from the soil The first stage by which plants make food is called PHOTOSYNTHESIS 4

5. by eating plants or... Animals get their food …... plant products, or (c) other animals Plants make their food by photosynthesis 5

6. Photosynthesis 6 Green plants take in carbon dioxide (CO 2 ) from the air They take up water (H 2 O) from the soil The plants combine the CO 2 with the H 2 O to make the sugar, glucose (C 6 H 12 O 6 ) 6CO 2 + 6H 2 O = C 6 H 12 O 6 + 6O 2 Oxygen (O 2 ) is a by-product of this reaction

7. C 6 H 12 O 6 CO 2 H2OH2O H2OH2O H2OH2O H2OH2O H2OH2O H2OH2O 6O 2 + 6 molecules of carbon dioxide combine with 6 molecules of water to make one molecule of glucose and 6 molecules of oxygen 7

8. Energy It takes energy to make CO 2 combine with H 2 O This energy comes from sunlight The energy is absorbed and used by a substance called chlorophyll 9

9. sunlight (energy) water carbon dioxide 9

10. Chlorophyll Chlorophyll is a green colored chemical It is present in the leaves of green plants The chlorophyll in the cells is packaged into tiny structures called chloroplasts The next slide shows a diagram of leaf cells with their chloroplasts 10

11. Leaf cells with chloroplasts cell wall nucleus chloroplast cytoplasm vacuole 11

12. All the reactions to combine CO 2 and H 2 O take place in the chloroplast sunlight water carbon dioxide in the chloroplast, carbon dioxide and water combine to make sugar 12 palisade cell of leaf

13. Cell structure of a leaf The palisade cells are in the uppermost layers of the leaf epidermis palisade cell ( photosynthesis) vessel (carries water) stoma (admits air) 13

14. Carbohydrates Glucose is one example of a carbohydrate Other examples are starch, sucrose and cellulose (in cell walls) Carbohydrate molecules contain the elements carbon, hydrogen and oxygen Living organisms can easily change one carbohydrate into another 14

15. What happens to the glucose? The glucose made by the chloroplast is either (a) used to provide energy for the chemical processes in the cell ( by respiration) (b)turned into sucrose and transported to other parts of the plant (c) turned into starch and stored in the cell as starch grains In darkness the starch is changed back into glucose and transported out of the cell 15

16. GLUCOSE storage e.g. starch in potato starch fruits other sugars e.g. seed germination energy cytoplasm protein cell walls cellulose 16