Im sorry for all these threads but Im finding some good information I thought you guys would enjoy:

From this website http://www.iupac.org/publications/pa.../6301x0123.pdf

Carotenoids are involved in several aspects of photosynthesis, notably light absorption and energy transfer to the reaction center (RC) complex and protection of the photosynthetic apparatus from damage by strong illumination.

LIGHT ABSORPTION BY CAROTENOIDS IN THE COMPLEXES
The location of the absorption maximum of carotenoids depends on the number of conjugated double bonds; in the case of 9 double bonds (p-carotene), it is located around 4 5 0 ~ min non-polar organic solvents. In the photosynthetic apparatus, the maxima are usually shifted to the red by ca. 30 nm (-1500 cm-l) (ref. 3). One possible explanation of this red shift is the presence of a point charge on _the_ po lypeptide (ref. 3)

There are several clear pieces of evidence for a protective effect of carotenoid against damage due to high photon density.

So having the additional 450nm(450-490nm) wavelength for the carotenoids would help plant growth in many ways.