Structures and Processes of Life: Plants Water vapour released from leaves
Plan, design, carry out and write up an investigation to show that water is lost through the leaves of a plant by transpiration.
Transport of Food
1. Glucose is sugar made in the leaves during photosynthesis. Some of this glucose is used by the leaves.
2. Some glucose is also stored in the stems and roots as starch. Sugars and starch are types of carbohydrates.
3. The glucose must be converted into sucrose (another carbohydrate) before it can be carried to all the parts of the plant by the phloem tissue.
Exchange of Gases
Stomata are small pores on the underside of leaves through which gases and water pass out of the plant. z z
The carbon dioxide needed for photosynthesis is absorbed from the atmosphere through the stomata. The oxygen produced as a waste product exits through the stomata.
zz
The oxygen needed for respiration enters the leaf through the stomata. The carbon dioxide produced as a waste product exits through the stomata.
Tropisms
Like all organisms, to survive plants must be able to sense and respond to changes in their environment.
The directional growth response of a plant to a stimulus is called a tropism. z z
Phototropism is the growth of a plant toward light. It allows it to get as much light as possible for photosynthesis.
z z
Geotropism is the growth of a plant in response to the force of gravity. The roots grow downwards to access water and mineral nutrients from the soil. The shoots grow away from the force of gravity.
Investigating phototropism and geotropism
Plan, design, carry out and write up an investigation of both the phototropic and geotropic growth response of suitable seeds or seedlings.
z Fig. 7.2.3
Phototropism is the growth of a plant toward light
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Sucrose transported around plant and may be stored as starch in stems and roots
Glucose made by photosynthesis
7.2
z
Fig. 7.2.2
The transport of food (carbohydrate) around a plant
