Exchanging Materials in Plants

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1 Exchanging Materials in Plants 1 of 23 Boardworks Ltd 2012

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3 3 of 23 Boardworks Ltd 2012 All living things need to exchange materials Plants need to obtain certain materials for healthy growth, including: sunlight water mineral ions oxygen carbon dioxide. Where do plants get these nutrients? Like all organisms, plants have to get materials for growth from their environment. Plants must then transport the nutrients to the part of the plant that needs them.

4 How are plants adapted for transport? 4 of 23 Boardworks Ltd 2012 The cell and tissue structures in different parts of the plant are adapted to allow transportation of essential materials. Leaves are entry and exit points for the gases needed by plants. Stems connect the roots to the leaves, flowers and fruits. They contain cells specially adapted for transportation of water, minerals and sugars. Roots absorb water and minerals from the soil.

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6 Roots and uptake 6 of 23 Boardworks Ltd 2012 Roots are adapted to obtain water and mineral ions. Roots are long and thin, and divide into many branches. This root network covers a large area in the soil. Near the growing tips of roots are root hair cells. These have projections that reach out between soil particles to increase the surface area for absorption. soil mineral ions and water molecules root hair cell

7 Which cells transport nutrients? 7 of 23 Boardworks Ltd 2012 Plants contain two types of cell adapted for transportation. Xylem cells transport water and minerals up the stem from the roots to the shoots and leaves. This transport occurs in one direction only. Phloem cells transport sugars produced in the leaves up and down the stem to growing and storage tissues. Both phloem and xylem form continuous systems connecting roots, stems and leaves. The phloem and xylem are arranged as vascular bundles.

8 Transporting water, mineral ions and sugar 8 of 23 Boardworks Ltd 2012

9 Demonstrate water movement 9 of 23 Boardworks Ltd 2012

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11 Exchange of gases in plants 11 of 23 Boardworks Ltd 2012 Plants use carbon dioxide and produce oxygen during photosynthesis. These gases move in and out of the leaves of plants by diffusion through the stomata. When the concentration of carbon dioxide inside the plant is low, it will diffuse in from the air, through pores in the leaves into the plant cells. If the concentration of oxygen is high inside the plant, it will diffuse from the plant cells through the pores and into the air.

12 Adaptations for gas exchange 12 of 23 Boardworks Ltd 2012 Leaves are adapted to increase the rate of diffusion of gases, and to reduce the rate of water loss by evaporation: A flat leaf shape increases the surface area for diffusion. Internal air spaces allow the gases to reach cells. A waterproof waxy cuticle reduces water loss. Thin leaves minimize the diffusion distance for gases. Guard cells control the opening and closing of the stomata to regulate how much water is lost through these holes.

13 How do gases enter and leave plants? 13 of 23 Boardworks Ltd 2012 Stomata are small holes, or pores, that can be found on the underside of leaves. A single hole is called a stoma. Each stoma is surrounded by two guard cells. When guard cells gain water, they curve outwards. This opens the stoma, allowing carbon dioxide in and oxygen out. Losing water causes the guard cells to come closer together, closing the stoma. This stops the movement of gases, but also prevents water loss.

14 Water and gas exchange in plants 14 of 23 Boardworks Ltd 2012

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16 What is transpiration? 16 of 23 Boardworks Ltd 2012 Transpiration is the loss of water from the leaves of a plant. Most of this occurs from the underside of a leaf, where the water vapour can leave through open stomata. In hot, dry and windy conditions, evaporation of water from plant leaves is more rapid. This loss of water at the leaf will cause more water to be taken up by the roots. However, if it cannot be replaced, the stomata will close to prevent wilting. Transpiration rates also vary naturally in response to environmental factors such as temperature and humidity.

17 Transpiration rates 17 of 23 Boardworks Ltd 2012

18 Why does transpiration vary? 18 of 23 Boardworks Ltd 2012

19 Transpiration true or false? 19 of 23 Boardworks Ltd 2012

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21 Glossary 21 of 23 Boardworks Ltd 2012

22 Anagrams 22 of 23 Boardworks Ltd 2012

23 Multiple-choice quiz 23 of 23 Boardworks Ltd 2012