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The Effects of Light on the Rate of Photosynthesis

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grace jenkins

on 8 January 2014

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Transcript of The Effects of Light on the Rate of Photosynthesis

Alternate Hypotheses
1.) The red light will result in the highest rate of photosynthesis.
2.) The green light will result in the highest rate of photosynthesis.
3.) The blue light will result in the highest rate of photosynthesis.
Alternate Predictions
1.) If alternate hypothesis 1 is accurate, then the most oxygen will be produced under red light.
2.)If alternate hypothesis 2 is accurate, then the most oxygen will be produced under green light.
3.)If alternate hypothesis 3 is accurate, then the most oxygen will be produced under blue light.
Experimental Question
Photosynthesis : The process in which plants use chlorophyll and energy from the sun to synthesize carbohydrates from carbon dioxide and water. Photosynthesis creates oxygen as a byproduct.
The Effects of Light on the Rate of Photosynthesis
Null Prediction
If the null hypothesis is accurate,
then the amount of oxygen produced
will be the same for all colors of light.
The rate of photosynthesis
will not change based
on the different colors of light.
The purpose of this lab was to determine whether different color lights had an effect on the rate of photosynthesis.
How do different colors
of light affect the rate
of photosynthesis on Heart-Leaf Philodendron?
Null Hypothesis
-Photosynthesis depends on a green pigment called chlorophyl, which is specialized for absorbing particular colors of light.
-Photosynthesis takes place within the chloroplast.
-Chlorophyll absorbs the light from the sun and plants combine carbon dioxide and water to make sugar and oxygen from the light

Chlorophyll Absorbance Spectrum
-Different wavelengths of light excite the electrons of the ETC by a different amount.
-Chlorophyll absorbs light most strongly in the blue and red spectrum
-Green pigment is reflected out because the pigment does not absorb it. This is
why leaves appear green.
Photosynthesis Measurements
Oxygen Gas Sensor
In order to determine the rate of photosynthesis, an Oxygen Gas Sensor was used to record the amount of oxygen given off from the Heart-Leaf Philodendron.
The Heart-Leaf Philodendron was kept under red, green, and blue light for three minutes.
Two trials were taken for each color of light.
Before each trial, the Oxygen Gas Sensor was calibrated.

The purpose of using three different colored lights (red, blue, green) was to determine whether the rate of photosynthesis would be affected with manipulated light color.

The purpose of using an Oxygen Gas Sensor was to determine the rate of photosynthesis based on the amount of oxygen produced in the three-minute time interval. The device recorded the amount of oxygen released as a product.

The purpose of conducting the experiment in three-minute time intervals for each trial was to get the results for a small time frame.

Heartleaf Philodendron
Scientific Name:
Family: Araceae
Long, winding stems that contain three- to four-inch leaves that are dark green and heart-shaped,
Common household plant that lives best in an average home humidity level
Requires moderate to low watering requirements
Toxic when eaten

Light Treatments
Lamp & Coverings
Red, blue, and green light was obtained by filtering the light from a lab lamp with red, blue and green coverings.
The lamp was held over the plant for approximately three minutes.
Plant Material
Philodendron scandens oxycardium
Independent Variable: color of light
Dependent Variable: amount of oxygen produced
Control Variables: temperature, pH, plant species, test chamber, time spent under light, light intensity
Control Group
White light trial
The null hypothesis was refuted because the different
colors of light resulted in different amounts of oxygen produced.

Alternate Hypothesis 1
was supported

We went directly from one light color to another without allowing the photosynthesis rate to stop before calculating it for the next wavelength of light.
The lamp may have been moved, causing a discrepancy in the amount of direct sunlight received by the plant.
Unexpected results
Blue light has a higher absorbance by plant photosynthetic pigments and high energy levels to excite chlorophyll electrons.
Red light also has a high absorbance rate and high energy levels to excite chlorophyll electrons, but not as high as blue light.
It would be expected that under blue light, Heart-leaf Philodendron would have the highest rate of photosynthesis.
However, it did not.
1.) The red light will result in the highest rate of photosynthesis.
The results show that red light produced the most oxygen during photosynthesis. The amount of oxygen produced under red light was greater than that under blue or green light.
Justification of the supported
and refuted hypotheses
Alternate hypotheses 2 and 3 were both refuted because both blue and green light produced less oxygen than the red light.
Suggestions for future work
To further study the effects of light color on the rate of photosynthesis experiments may be done using:
-Different color lights
-Different plant species
-Introduce different variables such as
temperature around the plant or pH levels
Possible Errors
"Heartleaf Philodendron." Guide to House Plants. N.p., n.d. Web. 06 Jan. 2014.


Photosynthesis Powerpoint
Full transcript