Question

The red and green lines in the graph shown below indicate the action spectra for chlorophyll pigment molecules during photosynthesis. The black line in the graph below shows the absorption spectrum for green plants.
Which of the following best explains the difference between the action spectra and the absorption spectrum in photosynthetic tissues?

• A. Some wavelengths of light are absorbed by accessory pigment molecules not involved in the photosynthetic process
• B. In very bright conditions, chlorophyll molecules absorb more photons of light than can be used in photosynthesis
• C. At higher temperatures, chlorophyll pigment molecules become less efficient and must absorb more photons that normal to excite electrons
• D. The process of photorespiration causes a discrepancy between the wavelengths of light absorbed and the excitation of electrons

Answer 1

The correct option is A Some wavelengths of light are absorbed by accessory pigment molecules not involved in the photosynthetic process

The action spectrum includes the wavelength of light absorbed by the photosynthetic pigments that drive the process of photosynthesis which usually involves the red and the blue light. But white light or sunlight contain other wavelengths of light within the visible spectrum that are absorbed by other pigments.

For example pigment phytochrome absorbs far red wavelength of light responsible for photoperiodism. Similarly Cryptochromes, phototrophins etc absorb other wavelengths of the visible spectrum

The only wave length that is more reflected than absorbed is Green

So, the correct answer is 'Some wavelengths of light are absorbed by accessory pigment molecules not involved in the photosynthetic process'