Page 6 - LN-PHOTOSYNTHESIS IN PLANTS

nm).
Action Spectrum
It is the curve that depicts the relative rates of photosynthesis at different
wavelengths of light. Now another graph given below, shows the wavelength at
which maximum photosynthesis occurs at blue, violet and red wavelength in a plant
(which is shown by chlorophyll-a).

Hence, this concludes that chlorophyll-a is the chief pigment, which is majority
responsible for the photosynthesis.The another graph given below show the action
spectrum of photosynthesis, which coincide closely to the absorption spectrum of
chlorophyll.

Hence, all three graphs together shows that the major part of the photosynthesis
takes place in the blue and red regions, while some of the photosynthesis takes
place at other wavelengths also in the visible spectrum.
Apart from chlorophyll-a (the major pigment,) which is mainly responsible for
trapping of light, other thylakoid pigments such as chlorophyll-a, xanthophylls and
carotenoids also absorb light, transferring energy to chlorophyll-a. These pigments
are called accessory pigments.
These pigments enable a wider range of wavelength of incoming light to be utilised
for photosynthesis and also provide protection to chlorophyll-a from photooxidation.
Photosynthetically Active Radiation (PAR)
The region of wavelength in which photosynthesis takes place normally. It ranges