Effect of light intensity on rate of photosynthesis on elodea plant

Essay by dilraboHigh School, 10th gradeB, November 2014

download word file, 18 pages 0.0


GROUP MEMBERS: Maritoni Valencia, Sangita Tamang, Ryutaro Seiki and Mao


Light intensity is one of the factors affecting the rate of photosynthesis. Other factors are concentration of carbon dioxide, temperature and to a lesser degree, water. Light intensity directly affects the light-dependent reaction in photosynthesis and indirectly affects the light-independent reaction.

Light is a limiting factor when the light intensity is too low to allow the light-dependent reaction to proceed at its maximum rate. Light is not normally a limiting factor except for plants in forest understory of other shaded plants. Very high light intensities may slow the rate of photosynthesis due to bleaching of chlorophyll. However, plants exposed to such conditions usually have protective features to include thick, waxy cuticles and hairy leaves.

Research Question: How does the light intensity affect the rate of photosynthesis?


How will this be measured?



Independent Variable

Light Intensity

A light sensor will be used in order to measure the light intensity


900-8400 lux (+/- 100lux)

Dependent Variable

Rate of Photosynthesis

The amount of bubbles produced over 30mins will measure the rate of photosynthesis.

Number of bubbles

2 - 1380 bubbles

(+/- 1 bubble)

Controlled Variables:

Controlled Variables


Possible effect on results

Amount of Water

Milliliters (ml)

If the amount of water is different from each plant, then the

Temperature of Water

Degree Celsius (°C)

The temperature of the water must remain constant because it acts as a heat shield and if the temperature fluctuates, it affects the rate of photosynthesis

Length of Plant

Centimeters (cm)

In order to keep the amount of chloroplast in a plant more equal with all the specimens, the length must remain constant.


Centimeters (cm)

The ruler is used to measure the distance between the...