Green light is often considered "bad" for photosynthesis because it is poorly absorbed by chlorophyll, the primary pigment responsible for capturing light energy in plants.
Chlorophyll Absorption Spectrum
Chlorophyll, the pigment that gives plants their green color, primarily absorbs light in the blue and red regions of the electromagnetic spectrum. It reflects green light, which is why plants appear green to our eyes. Because chlorophyll doesn't absorb much green light, that portion of the spectrum contributes less to the overall photosynthetic process.
Impact on Photosynthesis
Since chlorophyll absorbs less green light, less light energy is available to drive the light-dependent reactions of photosynthesis. These reactions convert light energy into chemical energy (ATP and NADPH), which are then used to power the Calvin cycle and produce sugars. A lower absorption rate translates directly to lower photosynthetic efficiency compared to light in the blue and red wavelengths.
Why Not "Bad," Just Less Efficient
It's important to note that the term "bad" is somewhat misleading. Plants can still use green light for photosynthesis, just less efficiently. Other pigments, such as carotenoids and phycobilins, can absorb some green light and transfer the energy to chlorophyll. Additionally, some green light might still be absorbed directly by chlorophyll, albeit less effectively than blue or red light.
Summary
In essence, green light is "bad" for photosynthesis in the sense that it is significantly less efficient at driving the process compared to blue and red light due to the absorption characteristics of chlorophyll. Plants prioritize the absorption of blue and red light for maximum energy capture.
