Which color of visible light is most effective in driving the light reactions of photosynthesis in green plants?

• A. Red and blue light
• B. Green light
• C. Yellow light
• D. Infrared light

Answer: (A)

Verified step by step guidance

1. Understand the concept of photosynthesis: Photosynthesis is the process by which green plants convert light energy into chemical energy stored in glucose. The light reactions occur in the chloroplasts and depend on pigments like chlorophyll to absorb light.
2. Learn about chlorophyll's absorption spectrum: Chlorophyll, the main pigment in green plants, absorbs light most effectively in the red (around 650-700 nm) and blue (around 400-500 nm) regions of the visible spectrum. It reflects green light, which is why plants appear green.
3. Analyze the options: Green light is reflected rather than absorbed, making it less effective for photosynthesis. Yellow light is absorbed to some extent but not as efficiently as red and blue light. Infrared light is outside the visible spectrum and does not drive photosynthesis.
4. Connect the absorption spectrum to the light reactions: The light reactions rely on the energy absorbed by chlorophyll to excite electrons, which are then used to produce ATP and NADPH. Red and blue light provide the optimal wavelengths for this process.
5. Conclude that red and blue light are the most effective in driving the light reactions of photosynthesis in green plants, based on the absorption properties of chlorophyll.