Effect of light intensity on rate of photosynthesis on elodea plant

Topics: Photosynthesis, Carbon dioxide, Oxygen Pages: 36 (4595 words) Published: November 17, 2014
LIGHT INTENSITY AND PHOTOSYNTHESIS LAB REPORT

GROUP MEMBERS: MARITONI VALENCIA, SANGITA TAMANG, RYUTARO SEIKI AND MAO

INTRODUCTION:

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?

VARIABLES:

HOW WILL THIS BE MEASURED?

UNITS

RANGE

INDEPENDENT VARIABLE

Light Intensity

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

Lux

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

UNITS

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.

Ruler

Centimeters (cm)

The ruler is used to measure the distance between the test tube and the plant. Therefore if the ruler is not the same, the measurements may differ due to different increments. Moreover, this will affect the rate of photosynthesis as the light intensity will increase if the plant is closer to the light source.

Amount of bicarbonate solution

Milliliters (ml)

The amount of bicarbonate solution will affect the amount of CO2 that each plant will receive. Thus if the amount of carbon dioxide fluctuates, then it would be considered as an independent variable.

Amount of lights in the room

No unit

The amount of lights in the room affect the light intensity, thus affecting the entire experiment.

HYPOTHESIS:

If the light intensity increases then the rate of photosynthesis will increase, although it will plateau if the intensity increases because the amount of light affects the production of oxygen

METHOD FOR CONTROLLING:

Variable

Method for controlling

Amount of water

The amount of water will remain constant through measuring the same type water in the same beaker at the volume of 800 ml.

Temperature of water

The temperature of the water will be measured with a thermometer and will be at a constant 25℃.

Length of plant

The length of the plant will be 10 cm each, using a ruler.

Ruler

The ruler used to measure the distance of the light from the plant will remain constant as the same ruler will be used.

Amount of bicarbonate solution

The amount of bicarbonate solution will remain at a constant volume of 25ml for all four plants.

Amount of lights in the room

The lights in the room will remain constant as the artificial lights will be turned off and the windows will be shut with curtains.

MATERIALS:

Elodea plants

Lamp

Beaker (1000mL)

Water

Test tube (30mL)

Bicarbonate solution (baking soda in water)

Masking tape

Thermometer

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