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Question:

advantages of having accessory pigments?

what the book says is that they 'harvest additional wavelengths.' i don't know what this means to how its an advantage.. can somone explain?

Answer:

in leaves accesory pigments are important because chlorophyll the main plants pigment are easilly broken down by low temperature. if chlorophyll, the green pigmnet is broken down accesory pigments give the leaves its color, usually orange, yellow
Each photon has a particular wavelength, determined by the photon's energy. A pigment such as chlorophyll can only absorb photons in particular wavelength bands, matching the energies of available electron transitions to excited states. For chlorophyll, these bands are in blue and red -- the green color of most leaves is due to the waste light that is not absorbed by chlorophyll, while red and blue photons can be absorbed and used to power photosynthesis. An accessory pigment can absorb a photon that has a wavelength (color) outside of the bands that chlorophyll is able to absorb and can pass some of the absorbed energy on to chlorophyll, getting rid of the excess energy in another form, such as heat. A pigment might be tuned to absorb a photon of yellow light; the absorbed energy, stored in the excited state of an electron, is called an exciton (the photon becomes an exciton, so energy is not created or destroyed). The exciton can be passed to a chlorophyll, but only with the same energy as the red photon that the chlorophyll could normally absorb directly. The excess energy, the difference in energy between the yellow and red photon, must be dissipated in another form. This process allows a plant to harvest photons that would otherwise be unavailable to its photosystems. Consider how this would be an advantage to a plant living on a shaded forest floor, or to a planktonic cyanobacteria floating in the water below other photosynthetic algae, in regions where photosynthetically useful photons are scarce.

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