Nutrition in Plants (part 1): Structure of a plant and its leaves to facilitate photosynthesis

1. Nutrition in Plants Chapter 7

2. Recall: ? Give the word equation of photosynthesis chlorophyll Carbon dioxide + water Carbon dioxide + water glucose + oxygen + water glucose + oxygen + water sunlight ? ? Give the chemical equation of photosynthesis Give the chemical equation of photosynthesis chlorophyll 6H2 2O O 6CO 6CO2 2+ 12H + 12H2 2O O C C6 6H H12 12O O6 6+ 6O + 6O2 2+ + 6H sunlight

3. Importance of photosynthesis 1. During photosynthesis, carbohydrates formed can be converted to fats, protein and other organic compounds ? food for animals 2. Allows animals who feed on plants to obtain energy as photosynthesis converts energy from the sun to chemical energy 3. Fossil fuels are a store of energy derived from sunlight through photosynthesis 4. Maintains O2and CO2balance in atmosphere

4. Lesson Objectives: ? To name the various parts of a plant ? Structure of the leaf ? Adaptations of the leaf to plant survival

5. What is a plant? Like you, plants: Like you, plants: • • are made of cells. are made of cells. • • need food to get energy and materials with which to need food to get energy and materials with which to grow grow • • respond to the environment with many behaviors respond to the environment with many behaviors Unlike you, plants: Unlike you, plants: • • can make their own high energy food from low energy can make their own high energy food from low energy molecules molecules • • can keep growing and can often replace missing body can keep growing and can often replace missing body parts parts • • do not have nerves or muscles, so they cannot think, do not have nerves or muscles, so they cannot think, feel or move feel or move

7. Branch

9. Venation vein network mid-rib branch veins

10. Label the parts of a leaf 5 8 4 7 6 3 2 1

11. Refer to page 129 textbook (no chloroplasts) (no chloroplasts)

12. Leaf Structure

13. Label the cells in the leaf upper epidermis cuticle palisade mesophyll spongy mesophyll Intracellular spaces lower epidermis stoma

15. Main site of photosynthesis The mesophyll which lies below the upper epidermis is the main site of photosynthesis Consists of 2 regions: 1. Palisade tissue 2. Spongy mesophyll Cells contain numerous Cells contain numerous chloroplasts chloroplasts which enable them to absorb max. sunlight them to absorb max. sunlight for photosynthesis for photosynthesis which enable

16. Stomata stoma guards cells ? Minute openings bounded by 2 guard cells

17. Guard cells ? Bean-shaped ? Contain chloroplasts ? Only epidermal cells that can make sugars ? Regulates the loss of water and gaseous exchange in the leaves of a plant How?

18. Structure of stomata

19. Action of guard cells 1. The water potential in the guard cells is lowered by i) sugars produced during photosynthesis ii) high K+ions (increased with sunlight exposure) 2. Water enters the guard cells by osmosis 3. Guard cells swell and become turgid 4. Because the guard cells have a thicker cellulose cell wall on one side of the cell (the side around the stomatal pore) ? the swollen guard cells become more curved and pull the stoma open

21. Gaseous exchange in the leaf of a plant

22. Gaseous exchange in the leaf of a plant ? The exchange of oxygen and carbon dioxide in the leaf (as well as the loss of water vapour) occurs through pores called stomata (singular = stoma) Back http://web.ukonline.co.uk/webwise/spinneret/plants/leafst.htm

23. Entry of carbon dioxide In daylight, photosynthesis occurs Carbon dioxide rapidly used up Carbon dioxide concentration in leaf becomes lower than atmospheric air Diffusion gradient exists Film of water on surface of mesophyll cells so that carbon dioxide can dissolve; dissolved carbon dioxide diffuses into the cells Carbon dioxide diffuses from the external environment through the stomata into the air spaces in the leaf

24. Activity: ? Predict why oxygen diffuses out of the leaf and into the atmosphere.

25. How do we distinguish between the xylem and phloem?