Investigating the Factors that Affect the Rate of Photosynthesis

Investigating the Factors that Affect the Rate of Photosynthesis

Aim: I will be investigating how light intensity affects the rate of

photosynthesis, whether it decreases or increases the rate of

photosynthesis.

Background Knowledge: Photosynthesis is the process by which plants

make their own food. For photosynthesis to occur, plants need:

· Light energy from the sun

· Chlorophyll to absorb light energy

· Carbon dioxide from the atmosphere and from respiration in plant

cells

· Water which is absorbed by the roots and transported to the leaves

by the xylem tubes.

Photosynthesis can be summarised by the equation:

[IMAGE] 6CO2 + 6H2O C6H12O6 + 6O2

The reactants are Carbon dioxide and Water; the products are Glucose

and Oxygen.

The factors that affect the rate of photosynthesis are:

· Light intensity- if the light is brighter, then the rate of

photosynthesis increases and visa versa.

· Water supply- if a plant cannot absorb enough water, then the rate

of photosynthesis decreases.

· Carbon dioxide concentration- if the percentage of carbon dioxide in

the atmosphere increases, so does the rate of photosynthesis.

· Temperature- if the temperature increases, then the rate of

photosynthesis also increases, (however, temperatures above 40OC can

damage a plant and photosynthesis stops because the chlorophyll gets

too hot).

The factor I will be investigating is light intensity; how it affects

the rate of photosynthesis.

The factors I will be keeping constant are:

· Water supply- by using same millimetre of water each time.

· Temperature- by using a thermometer to make sure the water is at the

temperature each time.

· Carbon dioxide- by not adding any thing in the water which increase

the carbon dioxide level, such as Hydrogen carbonate.

By keeping these factors constant I will only be investigating how

light intensity affects the rate of photosynthesis and the other

factors will not affect my results.

Prediction: I predict that the closer the lamp is to the plant the