The highest intensity of the Sun's radiation at the Earth surface is in the visible light wavelength ranges of between ~400 to 700 nm

Question

Questions:
a) Explain how plants maximize the uptake of sunlight energy. In your answer, consider chlorophyll and antenna pigment structures and functions.
b) Why does the photosynthetic part of plants appear green?
c) The leaves of some plants lose their green color in the fall, often appearing red or yellow. Use your knowledge of plant pigments to propose a possible reason for these color changes.
What will be an ideal response?

Answer 1

Answer:
a) Plants expand the energy wavelengths they can absorb by expressing several chlorophylls that have different absorption spectra. Chlorophyll a, which has a methyl (-CH3) group on the porphyrin ring, has a broad absorption spectrum, with maxima at about 420 and 660 nm, whereas chlorophyll b, which has a formyl (-CHO) group instead of the methyl group, absorbs more toward the center of the visible spectrum. Antenna pigments are arranged in the photosystem to collect light energy much like a radio antenna collects radio waves. The antenna pigments absorb photons and pass the energy to a neighboring chlorophyll molecule or accessory pigment by resonance energy transfer until it eventually reaches the reaction center chlorophyll.
b) Chlorophylls absorb mainly blue and red light, so plants appear green.
c) Some plants stop synthesizing chlorophylls as they become more dormant in the fall. Losing chlorophyll can expose the colors of other plant pigment molecules that are present longer.