Patterns in Nature Topic 11: Autotrophs Obtaining Essentials

1. Patterns in NatureTopic 11: Autotrophs Obtaining Essentials Part of the Patterns in Nature Module Biology in Focus, Preliminary Course Glenda Childrawi and Stephanie Hollis

2. DOT Points • Explain the relationship between the organisation of the structures used to obtain water and minerals in a range of plants and the need to increase surface area available for absorption. gly.uga.edu

3. Introduction Roots are the structures in plants for absorbing water and inorganic minerals. These structures have an extensive surface area which allows these substances to be absorbed efficiently. en.wikipedia.org

4. Water Uptake Plants need to absorb large quantities of water at a high rate to maintain their water balance. The uptake of water occurs by the process of osmosis. When water in the soil is at a higher concentration than the cell sap of root cells, water will move from the soil into the root by osmosis. revisionworld.co.uk explore.ecb.org

5. Water Uptake This is a passive form of transport and occurs slowly, so it is essential that the surface area of structures involved in absorption is increased. doctortee.com

6. Mineral Uptake The uptake of inorganic mineral salts is mainly by the process of diffusion. If the minerals are in a higher concentration in the soil than they are in the cells of the roots they will move passively into the roots. If diffusion alone is inadequate, facilitated diffusion and active transport may also be involved. cellspd5spering.wikispaces.com

7. Increased Surface Area The uptake of both water and mineral salts depends on a large area of contact between the roots and the soil water containing the dissolved minerals. An increased surface area in roots is achieved in the following ways: • Root hair zone • Extensive branching • Nature of cells utsa.edu

8. Increased Surface Area Root Hair Zone: • The root hair zone is in the younger part of each root, near the tip. In this region, the epidermal cells protrude outwards into the surrounding soil as microscopic extensions called root hairs. Their presence increases the surface area of a root up to 12 times! infovisual.info

9. Increased Surface Area Extensive Branching • Extensive branching of root systems in the mature regions increases the surface area of the root for absorption. dnowlan.ca

10. Increased Surface Area Nature of Cells • Water enters the root through the epidermal cells across the entire surface of the root system. The flattened nature of these cells increases their exposed surface. blog.lib.umn.edu

11. Movement of water and minerals Water and minerals that enter the root through the epidermal cells, particularly through the root hair zone, move across the root to the water conducting tissue called xylem, found in the centre of the root. Water moves by osmosis through the cells. Bio in Focus Text

12. Movement of water and minerals The water and minerals then move across the cortex, along a gradient, into the central vascular tissue. The vascular tissue in the centre of the root is continuous, passing up the stem and into the leaves as ‘veins’ in the leaf, serving as the main transport tissue in the plant. worldswithwords.wordpress.com

13. Movement of water and minerals Veins are made of two types of tissue: xylem and phloem. • Xylem transports water and dissolved minerals to the leaf • Phloem transports sugars made in the leaves to the rest of the plant extension.oregonstate.edu

14. DOT Points • Explain the relationship between the shape of leaves, the distribution of tissues in them and their role. freerandomwallpapers.com

15. The Role of Leaves Leaves are the main photosynthetic structures in plants. Their primary function is to absorb sunlight and make food. They also carry out the function of transpiration. enchantedlearning.com

16. The Role of Leaves Leaves are structurally adapted to enable them to effectively function. They are made up of a number of different tissues, arranged in a highly organised way to maximise their efficiency. flickr.com

17. The Role of Leaves The structural features needed by a leaf to effectively photosynthesis are: • Large surface area, with an outer layer able to absorb light and carbon dioxide • Pores in the leaf surface for the exchange of gases with the environment • Cellsinside that contain chloroplasts to trap energy • A water transport system from the roots to the leaves • A food transport system from the leaves to other parts of the plant.

18. The Role of Leaves Leaves have an enormous diversity of shapes and sizes, but most are flattened in shape and relatively thin, resulting in a large surface area that is exposed to the sun. This allows the maximum absorption of light for photosynthesis hiltonpond.org

19. The Role of Leaves The surface of leaves is covered by a protective layer of cells, the epidermis. These epidermal cells protect the inner tissues and prevent evaporation. livingscience.co.uk

20. The Role of Leaves Within the epidermis, there are specialised cells called guard cells that control both the exchange of gases and the loss of water. waynesword.palomar.edu

21. The Role of Leaves The cells that occur in the middle layers (mesophyll) are responsible for most of the plants photosynthesis. There are two main types of cells found in this section: • Palisade Cells: elongated cells that contain numerous chloroplasts found immediately below the upper epidermis • Spongy cells: contain large air spaces and their main function is gaseous exchange. They are situated in the lower leaf.

22. The Role of Leaves Vascular tissue is distributed throughout the leaf which ensures that no cells are to far away from a source of transport. plantali.blogspot.com

23. The Role of Leaves

24. Homework Students to complete: -Student Activity ‘Table CD3.1 Comparing tissues in leaves’ (Bio in Focus Teacher Resource CD) **Reminder to hand out 2.2.1Plant Parts Handout