Difference Between Absorption Spectrum and Action Spectrum

Main Difference

The main difference between Absorption Spectrum and Action Spectrum is that Absorption Spectrum shows the absorption of light of different wavelengths by a pigment, whereas Action Spectrum shows the relative effectiveness of these wavelengths in photosynthesis.

Absorption Spectrum vs. Action Spectrum

Plants use light to get energy or food through photosynthesis. There are different types of photosynthetic pigments in plants that absorb the light of different wavelengths. But they absorb only the light that falls in the region of the visible spectrum, i.e. 390nm to 760nm. A graphical representation that shows the absorption of light of different wavelength by the pigment of a plant is known as its absorption spectrum. On the other hand, a graphical representation that shows the effectiveness of these different wavelengths in photosynthesis is known as an action spectrum. An absorption spectrum shows the relationship between the absorbing capacity of the pigment and the quality of light. On the flip side, an action spectrum shows the relationship between the different wavelengths of light and the photosynthetic activity. Chlorophyll absorbs the light of blue and red color whereas, carotenoids absorb the light of violet and blue color. On the other side, maximum photosynthesis takes place in blue and red light. Absorption of light of different wavelengths can be measured by using spectrometer while, In action spectrum, the rate of photosynthesis can find out by measuring the amount of oxygen production, carbon dioxide fixation, and NADP+ reduction, etc. According to experiments, the peak of the action spectrum of chlorophyll is the same as that of its absorption spectrum which indicates that chlorophyll acts as a primary pigment in photosynthesis.

Comparison Chart

Absorption SpectrumAction Spectrum
A graphical representation that shows the absorption of light of different wavelength by the pigment of a plant is known as an absorption spectrum.A graphical representation that shows the effectiveness of different wavelengths of light in photosynthesis is known as an action spectrum.
It Represents
It represents the intensity of light absorbed relative to its specific wavelength.It shows the relative efficiency of photosynthesis produced through the light of different wavelengths.
It Explains
An absorption spectrum explains the relationship between the absorbing capacity of the pigment and the quality of light.An action spectrum shows the relationship between the different wavelengths of light and photosynthetic activity.
Measurement
Absorption of light of different wavelengths can be measured by using the spectrometer.In the action spectrum, the rate of photosynthesis can find out by measuring the amount of oxygen production, carbon dioxide fixation, and NADP+ reduction, etc.
Examples
Chlorophyll absorbs the light of blue and red color but, carotenoids absorb the light of violet and blue color.Maximum photosynthesis takes place in blue and red light.

What is Absorption Spectrum?

An absorption spectrum is a plot that represents the light of different wavelengths absorb by different pigments of the plants. A solution of a pigmy is placed in a device known as a spectrometer that gives the wavelengths that are absorbed by the pigment. The light absorbed by the given pigment is plotted against the wavelength that gives its absorption spectrum. It explains the relationship between the absorbing capacity of the pigment and the quality of light. It represents the intensity of light absorbed relative to its specific wavelength. According to absorption spectrum chlorophyll absorbs the light of blue and red color but, carotenoids absorb the light of violet and blue color.

What is Action Spectrum?

An action spectrum is a plot that represents the effectiveness of different wavelengths of light absorbed by different pigments in photosynthesis. The rate of photosynthesis in an action spectrum can find out by measuring the amount of oxygen production, carbon dioxide fixation, and NADP+ reduction, etc. It explains the relationship between the different wavelengths of light and photosynthetic activity. It shows the relative efficiency of photosynthesis produced through the light of different wavelengths. According to the action spectrum of different pigments of plants, maximum photosynthesis takes place in blue and red light.

Key Differences

  1. A graphical representation that shows the absorption of light of different wavelength by the pigment of a plant is known as absorption spectrum whereas a graphical representation that shows the effectiveness of different wavelengths of light in photosynthesis is known as action spectrum.
  2. An absorption spectrum represents the intensity of light absorbed relative to its specific wavelength; on the other hand, an action spectrum shows the relative efficiency of photosynthesis produced through the light of different wavelengths.
  3. An absorption spectrum explains the relationship between the absorbing capacity of the pigment and the quality of light conversely; an action spectrum shows the relationship between the different wavelengths of light and the photosynthetic activity.
  4. Absorption of light of different wavelengths can be measured by using spectrometer on the flip side, in action spectrum, the rate of photosynthesis can find out by measuring the amount of oxygen production, carbon dioxide fixation, and NADP+ reduction, etc.
  5. The absorption spectrum of different pigments shows that chlorophyll absorbs the light of blue and red color but, carotenoids absorb the light of violet and blue color, on the other hand, action spectrum shows that maximum photosynthesis takes place in blue and red light.

Conclusion

Above discussion summarizes that the Absorption spectrum and action spectrum both play an important role to find out the rate of photosynthesis. An absorption spectrum is the graphical representation of absorption of light by different pigments; on the other hand, the action spectrum is the graphical representation that represents the action of different wavelengths of light in photosynthesis.

Janet White

Janet White is a writer and blogger for Difference Wiki since 2015. She has a master's degree in science and medical journalism from Boston University. Apart from work, she enjoys exercising, reading, and spending time with her friends and family. Connect with her on Twitter @Janet__White

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