Final answer:
Green light is least effective for photosynthesis because the chlorophyll pigments in plants, which absorb light, mostly reflect green light rather than absorb it.
Step-by-step explanation:
The color of light least effective in driving photosynthesis is green. This is because the pigments in plants, specifically chlorophyll a and chlorophyll b, which are primarily responsible for absorbing light during photosynthesis, do not readily absorb green light; rather, they reflect it, which is why plants appear green. On the absorption spectrum, blue and red lights are most effectively absorbed by these pigments. Green light, on the other hand, is mostly reflected, making it the least effective for photosynthesis.
An example that illustrates this concept is that if plants use only chlorophyll a and b for photosynthesis, and we have three plants grown under different colored lights (blue, green, and orange), the plant grown under green light would exhibit the least growth compared to blue and orange. This is due to the lower absorption of green light by the chlorophyll pigments. Therefore, blue and red light wavelengths contribute substantially more to the photosynthesis process.