1. Photosynthesis

2. LEARNING OUTCOMES Explain the roles and importance of photosynthesis
Describe the process of photosynthesis
Question the factors influencing the rate of photosynthesis

3. Exercise
In your group discuss what is required for photosynthesis to take place

4. Photosynthesis – in outline
Photosynthesis = light makes nutrition
Photosynthesis takes place in cells containing chloroplasts
chloroplasts trap the sun’s energy in chlorophyll
This energy is then converted into food for the plant: principally sugars and starch
Sunlight
Carbon dioxide
Water
Oxygen
Glucose is produced to nourish the plant

5. The photosynthesis equation
The photosynthesis equation is as follows:
carbon dioxide + water + energy
glucose + oxygen
6CO2 +6H2O + energy
C6H12O6 + 6O2

6. Exercise
In your group discuss why you think photosynthesis is important in plant life,

7. Why photosynthesis is important
It provides food for plants for growth and repair
Plants in turn provide food for the rest of the food chain
Photosynthesis is the only natural process which:
uses carbon dioxide
and
releases oxygen back into the atmosphere

8. Exercise
In your group list what the main ingredients are in the process of photosnthesis

9. The ingredients of photosynthesis
Water. The plant absorbs water from the soil through root hairs – by osmosis
Carbon dioxide. The leaf obtains carbon dioxide from the air through pores in the epidermis (the ‘skin’ of the leaf) called stomata – by diffusion
Light energy. The cells of the epidermis are transparent to allow sunlight to pass through to the mesophyll cells which contain the chloroplasts.

10. Ingredients for photosynthesis
Sunlight passes through the epidermis to reach the mesophyll cells
Water passes from the roots by osmosis
Carbon dioxide enters through the stomata by diffusion

11. The products of photosynthesis
The glucose produced by photosynthesis is used in different ways:
It may be used by respiration to create energy.
It may be converted into starch and stored within the leaf, inside the chloroplasts.
It may be converted into sucrose and transported to other parts of the plant.
It can then be converted back into glucose, for energy, or starch, for growth or storage.
It may be converted into other organic substances such as cellulose (a carbohydrate) or amino acids (proteins).

12. The rate of photosynthesis
Sunlight. As light increases, so does the rate of photosynthesis up to a maximum. A plant cannot photosynthesise in the dark.
Temperature. The second stage of photosynthesis is sensitive to temperature: the optimum temperature is degrees Celcius.
Carbon dioxide. In very warm weather the stomata may close to reduce water loss. When this happens, carbon dioxide cannot enter the leaf and photosynthesis may stop.

13. Conclusion
From todays lesson what are your views in relation to photosynthesis?
Will you now look at plants in a different way.
Will it help you now identify when a plant is not healthy.

14. Homework
Research the following:
Chlorosis
Necrosis