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Science And Plant Lighting


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#1 KnuckleDragger

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Posted 18 September 2011 - 11:41 AM

I'm putting this here for the people who are interested in the science of plant lighting.

http://www.controlle...nf/Contents.htm

Yes, it will make your brain hurt a bit but it's good for you. :)

And something a bit cannabis specific.

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#2 teddys head

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Posted 19 September 2011 - 02:46 AM

thanks KD :)

mind boggling or what :D :)


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#3 JackBeNimble

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Posted 19 September 2011 - 03:43 AM

Interesting stuff indeed KD, even more interesting due to the fact that the LED's that I recently started using, use a 525nm green LED as opposed to white. Something to do with Quantam Efficiency?
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#4 KnuckleDragger

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Posted 19 September 2011 - 09:32 AM

Interesting stuff indeed KD, even more interesting due to the fact that the LED's that I recently started using, use a 525nm green LED as opposed to white. Something to do with Quantam Efficiency?


Yeah, how we look at plant growth has changed over the last few years. The old way of looking at plant light usage was to take leaf sample and examine them. Using new technologies we can study the plants while they are actually growing. A few plants light usage curves do look like the old classic examples but most plants have been discovered to make use of green light and plants like corn and cannabis make a lot of secondary compounds in the green range and even a fair bit of the photosynthetic reactions. If your LED's are using some green it indicates that someone has read the technical ag science literature from the last few years.
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#5 FlowerBurner

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Posted 28 December 2011 - 12:35 AM

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thanks KD
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#6 froggymountain

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Posted 29 December 2011 - 11:53 PM

Fascinating article KD. Especially the part about gradual illumination and darkness. It appears that plants are more productive when light is gradually increased and decreased. "Under the gradually increasing light of a diurnal light regime, the midday level of Rubisco activation state was nearly 100% and the RuBP level was about twice Rubisco binding site level. By contrast, when light increased to a maximum rapidly, as often occurs under growth room conditions, the midday level of Rubisco activation state was maintained at only 60% throughout the day." Consequences of Rapidly Initiated or Gradually Changing Irradiance http://www.controlle...Geiger text.htm Does anyone have any experience with Dimmable ballasts and lights? Were/Are the results significantly better? Geiger points out that although plant growth may appear "stimulated" under some lighting conditions, compounds produced by the plants are not the same quality, quantity or both. Perhaps a full-spectrum bulb with a dimmable ballast and programmable controller is ideal. Experiences anyone? Perhaps ramping light to full output and ramping down can be a key to more natural and better medicinal compound quality of plants - not to mention healthier plants.
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#7 froggymountain

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Posted 30 December 2011 - 12:28 AM

hefty reading. OK, I read through the list as far down as LED lighting. NASA early results (1994) indicated that RED and BLUE are the key colors for plant development (full spectrum not required): http://www.controlle...a/Bula text.htm "Flowering and seed development of several species of plants grown under a combination of red light emitting LEDs supplemented with 30 ╬╝mol.m-2.s-1 of blue light were similar to plants grown under light from cool-white fluorescent lamps. Thus, normal plant growth and development can be expected with most , if not all, plant species when grown under red light emitting LEDs as the source of photons for photosynthesis and supplemented with a small quantity of blue photons to meet the photomorphogenic requirements involved in normal growth, development, and maturation." "Stomatal Response" "The classical observation that stomates open in light and close in the dark is an over simplification of stomatal response as it relates to stomatal conductance of CO2 into the leaf. A number of internal and environmental conditions are involved in this critical plant response. From the standpoint of using red light emitting LEDs, Sharkey and Raschke, (1981), reported that stomatal opening was most responsive to light in the blue region of the spectrum, with a peak response being at approximately 450 to 460 nm (Figure 10). However, red photons provide sufficient signal for stomata to open so that the effects of low stomatal conductance under red light can only be overcome by increasing the concentration of CO2 to higher than ambient levels (Tennessen, et al., 1994). We have recently determined that providing a low level of blue photons from blue light emitting LEDs increases stomatal conductance and has the same effect on photosynthetic rates as was the reported effect of high CO2 concentrations (unpublished data)." Apparently, less power of illumination is required to get similar results in an "artificial environment".
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#8 tikidood

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Posted 30 December 2011 - 11:11 AM

Okay , this is probably gonna "Blow back" at me...lol I have actually been using twin 600 hps . I "over lap" the 2 lights by 3 hours ( ie : first light on for 6 hours while light second light comes on 3 hours prior to the first going off). While i know i dont need that much light in my 5'x5' garden ( flower room) the simple act of lights coming on and off "seems" to have a significant growth factor i have not seen before. Same strains, lights etc. BUT i seem to get more "foxtails" and hash tips in this current method. Once the current run is done i will be able to crunch the numbers to see if i finally get the 1 gram per watt goal of DANKNESS !! Mahalo ~"
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#9 froggymountain

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Posted 30 December 2011 - 09:00 PM

tikidood: that is "kinda" gradual, or at least graduated lighting. There is likely something to it. I checked around and Quantum and Lumatek sell "dimmable" ballast (there are others). Quantum employs a stepped switch (all of them do) on the end that takes it from 400 to 600 to 1000W - dimmable in a certain sense but not truly gradual. The intent of the switch is to facilitate a one-bulb option and in some cases several bulb wattages in one unit. The NASA experiment was done with a shutter and filters. No one I could find has a programmable system that mimics a sunrise or sunset - where a true ramp up and down is possible. If you don't mind manual switching during the cycle, there are options. Anyone know of a programmable unit?

Edited by froggymountain, 30 December 2011 - 09:32 PM.

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#10 mediuseA

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Posted 31 December 2011 - 12:31 AM

They make them for reef tanks and pet enclosures. Will do a lil research and post the results. muA
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#11 KnuckleDragger

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Posted 01 January 2012 - 12:12 AM

I've been trying to find time to put up some answers but reality keeps whacking me up side the head, maybe in the morning...maybe. xmassmiley40.gif

#12 KnuckleDragger

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Posted 30 September 2015 - 01:05 PM

bump


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