Antenna Pigments and short wavelength light

[pingrybioguy]

I know that the reaction center chlorophylls absorb maximally at 700 and 680 nm, and that antenna pigments absorb light of other wavelengths. I know that the antenna pigments pass this energy by inductive resonance to the reaction centers. Here is the question:

700 nm light (red) has E = 1.77 eV
400 nm light (violet) has E = 3.1 eV

If we use only 1.77 eV of a violet photon, the remaining 1.33 eV is not enough to funnel into P700. So, is it lost as heat? 1.33 eV is 932 nm which is in the infra-red.

Thanks.

[JackBean]

yes, it is of course emited as heat

[pingrybioguy]

Thanks Jack. The textbooks do not explicitly state this and some students, knowing that blue light has extra energy, might think that the antenna complex can split the light into two 'useful' packets of energy.

As a follow-up, here is an experiment I intend to have my students do next year. I'd like your input on pitfalls and any tweaks.

I will give them breadboards with red, green, blue and white diodes (the r, g & b have relatively tight emission spectra). I expect them to control intensity by measuring photon flux density by adjusting the number of LED's to get comprable outputs. Then we will grow fast plants under each different light treatment and measure height and dry mass. I assume that this will show similar growth in red and blue, but less in green.

Any input would be greatly appreciated.

[JackBean]

yeah, I think that should work. With the green light you should probably get etiolated plants, like grown in dark...