In the designation P 680, the subscript represents what characteristic of the pigment?

The designation P680 refers to a specific pigment found in photosystem II, which is crucial for the process of photosynthesis. The subscript 680 indicates the wavelength, measured in nanometers, of light that this pigment absorbs most effectively. Specifically, P680 absorbs light at around 680 nm, which is in the red region of the light spectrum. This absorption is critical for the pigment's role in capturing light energy to drive the photosynthetic process.

In the context of photosynthesis, different pigments absorb light at different wavelengths, making this characteristic vital for the efficiency of energy capture in plants. By knowing that P680 signifies the specific wavelength of light absorbed, one can understand how plants are adapted to utilize available light for photosynthesis effectively.