In most green plants, which color (wavelength range) of visible light will maximize the rate of photosynthesis?

• A. Red light (approximately 650–700 nm)
• B. Yellow light (approximately 570–590 nm)
• C. Infrared light (greater than 700 nm)
• D. Green light (approximately 500–550 nm)

Answer: (A)

Verified step by step guidance

1. Understand that photosynthesis primarily depends on the absorption of light by pigments in the chloroplasts, mainly chlorophyll a and b.
2. Recall that chlorophyll pigments absorb light most efficiently in the blue (around 430–450 nm) and red (around 650–700 nm) regions of the visible spectrum, while they reflect green light (around 500–550 nm), which is why plants appear green.
3. Recognize that light in the red wavelength range (approximately 650–700 nm) is highly effective in driving photosynthesis because chlorophyll absorbs it well, leading to a higher rate of photosynthesis.
4. Note that yellow light (570–590 nm) is less effective because it is not absorbed as strongly by chlorophyll, and infrared light (greater than 700 nm) has too low energy to drive photosynthesis efficiently.
5. Conclude that red light maximizes the rate of photosynthesis in most green plants due to its optimal absorption by chlorophyll pigments.