How can an absorption spectrum for chlorophyll and an action spectrum for photosynthesis be drawn?

SouravNovember 8, 2024

Answer

To draw an absorption spectrum for chlorophyll and an action spectrum for photosynthesis, one must understand the characteristics of each spectrum and the steps involved in creating them. Here’s how to approach this task:

Absorption Spectrum for Chlorophyll

Definition

The absorption spectrum shows the specific wavelengths of light absorbed by chlorophyll pigments, primarily chlorophyll a and b. This spectrum typically displays peaks at certain wavelengths where absorption is maximized.

Steps to Draw the Absorption Spectrum

1. Draw and Label Axes:
   • X-axis: Label it as Wavelength (nm), ranging from approximately 400 nm to 700 nm.
   • Y-axis: Label it as Percentage of Light Absorbed (%), ranging from 0% to 100%.
2. Plotting Data:
   • Identify the key absorption peaks:
     • Chlorophyll a: Peaks around 430 nm (blue) and 662 nm (red).
     • Chlorophyll b: Peaks around 453 nm (blue) and 642 nm (red).
   • Draw curves that spike at these wavelengths, indicating high absorption, and drop near the green region (around 500-550 nm), where absorption is low.
3. Smooth Curve:
   • Connect the points with a smooth curve to represent the continuous nature of absorption across wavelengths.

Action Spectrum for Photosynthesis

Definition

The action spectrum indicates the effectiveness of different wavelengths of light in driving photosynthesis, reflecting the rate of photosynthesis at various wavelengths.

Steps to Draw the Action Spectrum

1. Draw and Label Axes:
   • X-axis: Label it as Wavelength (nm), ranging from approximately 400 nm to 700 nm.
   • Y-axis: Label it as Rate of Photosynthesis (% of Maximum Rate), ranging from 0% to 100%.
2. Plotting Data:
   • Identify peaks corresponding to effective wavelengths for photosynthesis:
     • High rates at blue (around 430 nm) and red (around 660 nm).
     • A trough in the green region (around 500-550 nm) where photosynthesis is less effective.
3. Smooth Curve:
   • Similar to the absorption spectrum, connect the points with a smooth curve, showing peaks at blue and red wavelengths.

Comparison of Spectra

• Both spectra show similar patterns with peaks in the blue and red regions due to chlorophyll’s absorption characteristics.
• The action spectrum reflects biological effectiveness, while the absorption spectrum indicates physical absorption properties.
• The correlation between these spectra supports the idea that light absorbed at specific wavelengths effectively drives photosynthesis.