Use of LEDs to promote flowering

Use of LEDs to promote flowering

This Christmas a local store had strings of “super bright” LED Christmas lights available. The cost was a string of 60 for $1.99 and a string of 120 for $3.99. The LEDs are removeable so one could buy a number of strings and set up a string of all blue.

Titles: Effects of LED and LD at different wavelengths on the growth and flowering of roses.

Authors: Mori, Yasuhiro; Takatsuji, Masamoto; Harada, Junji.

Authors affiliation: Department of Chemistry, Faculty of Science, Tokai University, Kita-Kaname 1117, Hiratsuka, Kanagawa, Japan. Reza Kenkyu (2005), 33(8), pages 537-541.

Abstract: "We cultured rose tissues under irradn. of LED and LD at different wavelengths, and examd. their effects on the growth and flowering of roses. As a result, flower-bud differentiation was rarely obsd. under irradn. of red (660 nm) and green (517 nm) LED, but it was enhanced by irradn. of blue (465 nm) and blue-green (502 nm) LED. In particular, flowering was obsd. in 76 % of the samples irradiated with blue-green LED, which was the highest flowering rate. However, flowering occurred earlier by irradn. of blue LED than by that of blue-green LED, and the flowering position (node position) was lower by the former irradn. than by the latter irradn. The irradn. of LD (445 nm) demonstrated a higher flowering rate and earlier flowering than the irradn. of LED, but the growth rate was lower by the former irradn. than by the latter irradn. This may be because there are photoreceptors that absorb blue to blue-green light and induce flower-bud formation. Since the wavelength width of LD is smaller than that of LED, energy for the increase in the growth rate may have been suppressed, and used for the reproductive growth, resulting in the enhancement of flowering. "

The peak absorbance spectrum for chlorophyll “b” is roughly around 480 nm with a smaller peak around 630. The blue and blue-green LED wavelengths are certainly within the upper slopes flanking the larger “aqua-blue” peak. (Chlorophyll “a” - the universal chlorophyll - has nearly equal absorbance peaks around 425 and 675.) From this experiment, it would seem to reason then that perhaps chlorophyll b plays a role in flower development in roses, that is to say, the “photoreceptors that absorb blue to blue-green light and induce flower-bud formation” to which the scientists allude.

I would have expected the same pigment that triggers photoperiodism in plants, but I think that pigment is a pigment called phytochrome with absorbances in the far red end of the spectrum… I don’t know what its chromophore is – Unbelievably, you’ve actually got me wanting to dig up and review some organic chem literature.

Interesting experiment towards understanding the mechanisms of flower production and I’m very intrigued, but I’m not sure the application is all that practical. I would imagine that one could achieve the desired results simply with bigger (cheaper) broad spectrum lights having plenty of blue light in their spectrum. I’ll be interested to hear of your results.

The good news is that blue is one color that will probably be spectrally true in the LEDs. Blue from gallium nitride is a very common LED formula. Many of the other colors may not be spectrally pure as many manufacturers often coat LEDs with phosphors to create simulated spectral colors.

Let us know if you feel the results of your in-home experiment warrant a run on blue LED lights!

Good luck

-Philip

Philip, I do not plan on doing any blue light experiments. I try to prevent flowering so that the plants are big enough to survive the first winter.

I purchased the Christmas LEDs sets to create all red sets which I use to enhance germination, see:

Http://home.neo.rr.com/kuska/redlight.htm

And

Http://home.neo.rr.com/kuska/redlighthints.htm

And

Http://home.neo.rr.com/kuska/led.htm

And

http://home.neo.rr.com/kuska/new%20germination%20method.htm

Link: home.neo.rr.com/kuska/new%20germination%20method.htm