I need a botanist. Question about Pr, Pfr, and the need for red light

• Fact ,also ....
  
  
  Photosynthesis ( PS ,from now on .. ) is made on a basis of photon / quanta absolute numbers
  and not by energy contained/carried ....
  Excess energy is transformed to heat ,by both physical(molecule level ) and chemical(electron/atom level )reactions ...
  (water molecule vibration & long wl emission ,respectively .. and as simply ...)​

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heckler73 said:

Just to add some colour to this claim...

This is an HPS seen through a spectral diffraction grating at different levels of exposure:
View attachment 2601134

And here are some comparisons of different lights with their relative visible spectra
View attachment 2601132

I wonder what a light made from Hydrogen and Helium would look like? Hmmm



Really? I just punched in "Red Light effects on fruit production" into the university search engine and found this amongst many recent papers:

Response of Tomato and Pepper Transplants to Light Spectra Provided by Light Emitting Diodes


Abstract

Growing conditions during transplant production influence seedling quality and performance, transplant establishment, and subsequent yield. The effects of spectra combinations of blue, red, and white light, generated by monochromic light-emitting diodes (LEDs), on physiological and morphological characteristics of tomato (Solanum lycopersicum L.), cv. Kingston, and pepper (Capsicum annuum L.), cv. California Wonder, seedlings were investigated. Tomato and pepper transplants treated with monochromic red, or combinations of red with blue light, produced greater stem diameter, whereas blue light alone, or in combination with red, reduced transplant height. In tomato the most lateral branches were produced on seedlings under blue light, but pepper transplants were not affected. The most leaf area in tomato and pepper transplants was obtained under monochromatic blue or red light, respectively. Proline, an important compound related to plant stress tolerance, was produced at the highest level under blue light in both plants. For tomato, red light alone or in combination with blue or white light reduced the number of leaves required before the first cluster. This occurred in pepper transplants when higher ratios of red light (up to 100%) were applied. For both plants rates of first cluster formation and first yield were higher when combinations of blue and red lights (regardless of their ratio) were used. The most vitamin C was in fruit produced on plants developed from transplants grown under blue light. Fruit total soluble solids were also higher in tomato plants developed from blue light–treated tomato seedlings. There appear to be beneficial effects due to exposure of plants during seedling development to light spectra that extends beyond transplanting. The effects of light spectra appear to be genus or species specific. The LED technology did not differ from other technologies and has merit for production of some vegetable seedlings.


Now, one nagging question I have is WHAT WAVELENGTHS WERE THEY USING?
You think they would have measured that
Damn scientists!
But I don't know if that answers any of your questions...

Probably not...



Do you really need a PhD to answer that for you?
But as someone else noted, you're more likely to find God on here than a PhD...

Doesn't Govindjee cover this topic in his book on Photosynthesis?

View attachment 2601131
That's just something I dug up while looking at chapter 9... it doesn't answer the question of 60:40 ratios...



I don't know if you're confused,
but I sure am

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heckler73 said:

I just thought these two tables might be of use in deliberating the matter. I clipped them from that study I referenced earlier
It gives some insight into whether 60:40 even matters...

Actually, where did this 60:40 idea come from, anyway?

View attachment 2601348View attachment 2601349

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Induction87 said:

http://www.nvcc.edu/home/rgorham/Sites/courses/110/110_Powerpoint/a17bot_BW_(Responses_Hormones_Phytochrome_06)/tsld101.htm

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Induction87 said:

I don't have access to a university search engine. Universities, as you know, subscribe to hundreds of scientific journals and periodicals and have their articles electronically available. An AWESOME resource, if you're still in college.

Thanks for looking it up though. Like I said, I am just starting to study this stuff and was confused about the limited info I could find on google.

I appreciate all the input.

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Induction87 said:

At equal ppfd, it should not matter if the light is more red or blue, as long as there is enough red to maintain the 60:40
Prfr ratio.

Thanks!

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PurpleBuz said:

It does matter. Light in wavelengths from 300+nm all the way to 730 nm have a role in plant growth and behavior. Blue lights are the other half to day length setting patterns. Many species of plants are able to "sense" dawn, dusk and daylength with a combination of blue light daily patterns and red\far red. Pfr\Pr ratios has only been shown to effect the trigering of flowering in plants that require long dark periods. Overall productividty of a plant involves much more than just supplying a balanced 660nm\730nm ratio.

Another assumption that you are making is not quite right. The energy in bluelight is higher than in red light. A small amount of light around the 450 nm range packs a much bigger punch than the same amount of light in the 610 nm range. Using a balanced blue:red range one can saturate BOTH chlorophyll peaks, providing more total energy conversion.

I have also seen a number of serious scientifically based growers on RIU thinking that a balanced spectrum produces better than a primarily Yellow\Orange\red spectrum. Testing is ongoing with adding deep red (660) and Blue (420-450) to hps.
https://www.rollitup.org/led-other-lighting/638146-ultimate-flowering-spectrum.html

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