The rate of photosynthesis of a freshwater plant is measured using five spectral colurs. Which sequence of colours would give an increasing photosynthetic response? Smallest `rarr` Largest response

Options

A. Blue Green Yellow Orange Red
B. Green Yellow Orange Red Blue
C. Red Orange Yellow Green Blue
D. Yellow Green Orange Blue Red

Answer

To determine the sequence of colors that would give an increasing photosynthetic response in a freshwater plant, we need to consider the absorption spectrum of chlorophyll, which is the pigment primarily responsible for photosynthesis. Here’s a step-by-step solution:

### Step 1: Understand the Wavelengths of Light
- The visible light spectrum ranges from approximately 400 to 700 nanometers (nm).
- Different colors correspond to different wavelengths:
- Violet (400-450 nm)
- Blue (450-495 nm)
- Green (495-570 nm)
- Yellow (570-590 nm)
- Orange (590-620 nm)
- Red (620-700 nm)

### Step 2: Identify the Absorption Peaks of Chlorophyll
- Chlorophyll absorbs light most effectively in the blue (around 430 nm) and red (around 680 nm) regions of the spectrum.
- Chlorophyll has lower absorption in the green region (around 500-550 nm), which is why plants appear green.

### Step 3: Rank the Colors Based on Photosynthetic Response
- Based on the absorption characteristics:
1. **Red** light has the highest absorption and thus the largest photosynthetic response.
2. **Blue** light also has a significant absorption but less than red.
3. **Orange** light has moderate absorption.
4. **Yellow** light has lower absorption than orange.
5. **Green** light has the least absorption, resulting in the smallest photosynthetic response.

### Step 4: Sequence the Colors
- Therefore, the sequence from smallest to largest photosynthetic response is:
- Green < Yellow < Orange < Blue < Red

### Final Answer
The correct sequence of colors giving an increasing photosynthetic response is:
**Green < Yellow < Orange < Blue < Red**

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