Par Readings

chazbolin said:

When a plant has absorbed the energy it needs, as we measure by PPFD which values intensity and spectrums, when all of the chlorophyll absorption takes place the plant has reached 'saturation'. It does not need any more energy to complete what its particular RNA structure has programmed it to absorb at that level of growth its currently at.

When we look at the PAR curve for a terrestrial plant you want to spend as wide as energy as possible to more closely mimic solar energy which allows the plant to complete it's naturally programmed photomorphogenesis. We cannot recreate the sun but we can provide the plant the extended lighting integrals to meet its daily mole saturation count. With cannabis daily mole saturation is around 18 moles. Which with the proper wide spectrum lamps these PPFD values can be found in a 12-13 hr daily on cycle.

If the lamp is on longer then that or much of the energy it produces is well above PAR (look at the lamps spectral distribution graph) so as to 'fall' within red spectrums then the efficiency of the lamp should be questioned relative to entire analysis of cost/m2

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chazbolin said:

Good post but I might add that this is a complex topic and micromole readings alone represent a value in intensities calibrated for plant spectra. Of course this is better the lux, lumen or footcandle measurements but even those measurements are adjusted based on the meter being used for the kelvin temperature it's reading. So saying one fixture or lamp is better then another based on strictly PAR readings is not taking into consideration the plants entire photosynthetic absorption requirements.

Micromoles or uMoles represents intensity within the PAR region of 400-700 nanometers. Before dropping big coin on the latest and greatest you'll also need to know the spectrums being emitted within this wide range and that is measured in Photosynthetic Photon Flux Density. In other words I can have quantum meter or PAR meter, displaying PAR intensity @ 890 uMole reading in UV (veg) ranges that does in fact fall within the PAR spectrum but is missing or has lower intenities within the Red-Far Red regions that the plant needs for flower.

That is why PAR values are best defined in relative intensities, PPFD, over the entire PAR region. This can be seen by the mfg data usually on their home page for the light they are offering as a Spectral Distribution Graph that shows the entire PAR spectrum and the Relative Intensities that their lamp emits within PAR regions. As you look at the various manufacturers Specatral Distribution Graphs (if they even post them) keep in mind that energy consumed above the PAR values is wasted energy to the plant and results in excess heat to the indoor environment.

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brahbrahbinks said:

So basically all you're saying is that Par represents the INTENSITY and not the spectrum, so yes it would be unwise to purchase based solely on par measurements. I am making it a point that par should be an integral part in making a purchase and that companies need to make there numbers well known such as true wattage or actual draw. Most sites have caught on and now display actual wattage draw and even spectrum used, that is no longer such an issue. Penetration is really the only obstacle that leds really face as of now. We need to start demanding companies to release their numbers so customers can make an informed decision. Par meters dont measure values above par cause they would be above 700 and in the far red and infared which is heat.

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chazbolin said:

While there is little chlorophyll absorption above 700nm flowering and germination are still positively influenced by the presence of FR/IR wavelengths. The presence of a 730nm wavelength increases trichome layering. While there are those that don't feel quantum PAR meters don't need to measure these ranges north of 700nm and I would tend to agree since the meters are calibrated anyway (I have an algorithm that takes a standard lux meter and converts the measurements to PAR) and this would just be a widening of the calibration I would still refer anyone interested in knowing what the Relative Intensities of the lamps emitted spectrums refer to the manufacturers Spectral Distribution Graph, chart or Spectrum Analysis (whatever they're calling it). None of the LED mfg's tend to offer this data as an overlay of PAR values and their particular LED lamp spectra. Point me to any LED company that does and I'll stand corrected (to a point).

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chazbolin said:

The LED wavelengths shown on the AT120RB show peaks @ 470 & 630nm and are very narrow bandwidths.
The LED wavelengths shown on the AT120WR show a Veg level listed as 6,100K which is odd since we're dealing in quantum values but self corrects to 630nm for flower.

Take a look at any chlorophyll absorption chart and you'll see the missing spectrums that must be present at some levels to allow the plant to transition thru the entire growth cycle as veg-coratenoid-flowering/bud. A successful transition allows the plant to achieve what is known as the Emerson Effect. That is when the plant does not stress from missing wavelengths and grows to it's largest genetic capacity bearing the greatest abundance and quality of fruit. Narrow spectrums as you see here require the plant to delay growth and result in lowered Net Photosynthetic Action Spectra. That is lost energy that the plant should use for growing but instead try's to fully develop within the narrow LED bandwidths +/- 10 nm of half peak bandwidth that are available to it.

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parseeker said:

Very enlightened conversation. I am researching for my new LED light now. Would you mind recommending an acceptable solution from either Apache Tech, Lumigrow, Stealth Grow or another company. These appear to be good options based on my research (basically literature and videos) however, since I am not knowledgeable in this discipline I am hoping to obtain some suggestions from folks who are. Can you throw a bone over the fence? Cheers...

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PetFlora said:

Puff, www.ledgrowlightsreview.org reviewed the apache

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puffenuff said:

yeah ive read that but dude didn't even get his hands on one nor did he review the white+red and I don't think he put in much effort to taking to apachetech because I got ahold of them first try. How are you going to review a panel without even testing it? I don't share any of the same concerns as that reviewer. My review of the light will be much more reliable.

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