Light for vegetative growth vs flowering?

[Magnus A]

Hello

This is a statement Ross made recently in another thread

"The higher the number - the more it is designed for growth of leaves. The yellower it is the more it is designed for flowering."

I would like to have some references for this, becouse:

Light is absorbed and converted to usefull energy in the plants Photosystem I and Photosystem II. In this processes there is NO differentiation in red and blue light. The light is absorbed in an ANTENNA system and the ENERGY is transfered to the reaction centre. As the energy needed to make the reaction center work is quantified and all excess enrergy is lost as heat the system does not care if the light is blue or red. The Photosystem creates the energy carriers (NADPH and ATP) that the plants use for living. There is NO other light driven reactions in the plants that create energy for the plants.

What is the explenetion for the above statement?

I think but I do not know!
That the light intensity and the heat radiation from the different colored lightsource was significant different. That is the reason that it has been observed an different under badly controled experiments. This IF an experiment ever was performed....

The blue and red light gave different temperature and different light intensities that the plants reacted on NOT the wavelenght......


Why do I bring this up? Just becouse my own interest in rupicolous laelias and Sophronitis seams to indicate that they only flower realy good when they are abused with very high light intensities OUTDOOR and it seems that it is the blue to Ultraviolet light that is needed to initiate good flowering not the light. I have an thought that the light protection mechanism, were the plants "take care of" high energy light (blue and particular UV) create some metabolites that initiate flowering.... (temperature could also play me a joke but I think I see a difference in lants that is in the shade and in full sun on the same balcony, to few observation to draw any conclusion)


It got some what long nad a little to scientific but what do you think about this???
Ross is the blue vs red light just something that comes from an old orchidgrower that everyone lissened to and that thsi persons statement was always taken as the truth?


/Magnus

Sorry for any spelling misstakes

[Ross]

How about:

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I think you get the idea. For most orchid growers it's not an issue. But for Pot growers it tends to be. I also would worry about raddish and lettuce, as well. For orchids we want both. I think most of us have settled on 5000-6000K as the sought after target. It represents high noon at the equator, as for color temperature, and as such must be good, right? No, the color spectrum as per plants is a demonstrtated fact. I tried to include some quick links, but wasn't able to lay my hands on the scientific stuff as quickly. It's not a folk-tale (to be sure.) It is true that warmer Kelvin promotes blossoms and cooler promotes leaf growth. If you need more proof I will be happy to research for you.

[Magnus A]

Ross

I realy admire your input on alot of things but

I do not need prof! I wanted an explenaition..... Totaly different thing...

The first and third link is to a seller of lights, I cant find ANY useful information other than sales Statement that has no explenations

Second link discuss light penetration on a physics forum nothing that explain the biochemistry on growt vs flowering.....

The last link is also to public forums that does not discuss any explenation! They just use the statement as facts!

I know that I have seen some interresting references of actually experiments and not just statements from "common people" that has no or smal understanding of what happens in the plants...

Do you understand what I imply? That the statement of red and blue light actually is wrong due to one or two badly formulated statement by some old "guru" or a missinterpret experiments.

It is very easy to find the statements but almost impossibly to find the source. I hope you see what I am after....

Magnus

[Ross]

I see what you are after and promise to research (as could you ) the sources. I trust the science because it has held true for me. But if you want the source I will try to find it.

[Ross]

Does this help? The Physiology of Flowering Plants ... - Google Book Search You have to scroll thru lots of pages.

[Magnus A]

I am also serching Ross

But I am scared that there is no science that stand scrutiny behind this statement


On one forum I found this

"for veg you want to simulate summer so use 6000k, and use the the lower kelvin for flowering to simulate flowering in the fall (season changes)"

That for me is a statement based on growing cycle in the nature and there the growing season proced the flowering, that natural comes after growth. Little hard to get flowering first and growth later...... And then we have the temperature change between summer and fall.

As I said above! I want a plant physiological explenation NOT proof of a convinced community that just belive......


I continue to search

[Magnus A]

Thanks Ross

But no,
This book Chapter 6.5 discuss growth and states that light is NOT a requrement IF you could supply the nutrients needed. The book has NOTHING on red vs blue light!

/Magnus

PS I can ask around at work next week.... We have one professor in biochemistry and one in plant physiology. I am almost certain on their answers but I will ask anyway....

[kavanaru]

Magnus, the problem here is that you are looking only at the Photosynthesis process, and are not paying attention to the other physiological processes regulated by Pyhtochrome (absorving mainly red/far red) and Crytochrome (absorving mainly blue and UVA - there is another photoreceptor for UVB, but I do not remember its name).

It was long long ago that I had my Plant Physiology lessons (and I must admit it was not my favorite field!), but I can remember something regarding photoperiodism, wich is actually activated by different light temperatures (more than per hour of light itself!) and being regulated by Phytochrome. There was a "very elegant" experiment from McAlister et al. which gave basis for the discovery of the Phytochrome some years later, in which they demonstrated that germination was controlled by red and blue light, and once inhibited it coud be desinhibited by exposing the seeds to the other light temperature (there was another guy who did something similar with flowering, but I do not remember his name, and McAlister's expermient was more important)

If I remember correctly, activated Phytochrome would stimulate germination and leaf production, but would inhibit flowering (and if I remember correctly, in some plants also internodal stem elongation)...

as I said, I am just trying to remember my Physiology lectures (that was back to the late 80s / early 90s ) I do not remember the details, but the story was more or less as described above

I hope this helps

P.S.- "Sometimes, the proofs given by popular experience are more important that the facts given by a scientist ion a lab! Keep your eyes open!" <-- That was a statement that my Biostatistic prof told us in the very first day of the Biostats Semester at the university.. Then he added: "Remember that many of the greatest experiments in history are based on observation of popular experience"

[Magnus A]

Hello

I have been looking around in the literature today.
As Ramón write McAlister et al. found in the 1935 that germination was inhibited by far-red light (700-800 nm) this was confirmed by Borthwick et al. 1952.

BUT, and now to flowering…..
Red light with lower wavelength than 700 nm has been shown to INHIBIT flowering, this was shown by Dows in 1956! But this inhibition was canceled if irradiation with far-red light was added (above 700nm).
If you take a look on the spectra distribution of a 2700 Kelvin T5 tube there is a peak at roughly 720nm (far-red) that should prevent flowering inhibition! This peak is also present in a 6500 K tube.....

Boss et al. reviewed “multiple pathways in the Decision to flower” in The Plant Cell 2004. They write “In contrast to red light, far-red and blue light promote flowering.”

The literature show that blue light promotes flower and red light below 700 nm inhibit flowering. This inhibiting effect can be canceled if simultaneous irradiation with far-red (above 700nm) is present.

I have not looked into factors of growth, but clearly, for artificial lightning, the discussion of yellow contra blue light in the region 3000-6500 K is of no value for flowering. The possibly inhibition of flowering by the red light is canceled by the portion of the far-red light present in all tubes. Spectral distribution diagrams can be found on Osrams homepage. You can see that the red part between 650-700 nm is a minor component for the color temperature.

[Magnus A]

The statement that you could select flowering vs growth condition by altering the ratio between color temperature in the range 2700-6500 does not seem to be supported in the literature.... You could say that if you inhibit growth you only promotes flowering but why do that? You want both growth and flowering.