Lycopene
Zeaxanthin
B-carotene
400
500
Lutein
Chloryphyll b
Chlorophyll A
600
700
Wavelength (nm)
Fig. 1
The photosynthetic pigments absorb much of the spectrum.
It is important at this point to distinguish flux and energy. Light sources
generate so many micromoles of photons per second, which is a measure of
the flow (flux) of radiation. Each photon has a small amount of energy, and we
can measure this instantaneous flux in watts. If we accumulate this energy for
one second, we are measuring the energy in watt-seconds, or joules.
500-570 NM: GREEN
Even though chlorophyll A, chlorophyll B, and beta-carotene are not efficient
at absorbing green light, plants do still respond to it. In fact, there are
accessory pigments that harvest the light energy in this range
and transfer that energy to chlorophyll, though not to the same
degree of chlorophyll A, chlorophyll B, or beta-carotene (Fig.1).
46
Maximum Yield