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PAR (Photosynthetic Active Radiation) Meters and the Measurement of PPFD (Photosynthetic Photon Flux Density) to Grow Ant Plants


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There are quite a few posts on the forum where members describe their use of artificial lighting to grow ant plants.  The range of artificial lights mentioned include T5 HO fluorescent and metal halide. I did a search of the forum but did not discover any mention of LED lights.  I read some discussion about the efficacy of the lighting systems used and their effect on growth, vigor, and seed germination.  Artificial lighting is being used in greenhouses, terrariums, and plant stands by various growers on the forum.

Has anybody used a PAR meter to measure PPFD on their tables and used the information to adjust the amount of light that they are providing their plants to achieve better results?  Also, is anyone familiar with the technical literature to know if any field researcher has published any information regarding the measurement of temporal PPFD on ant plants in nature?

I use the 6500K Barrina LED lights on my plant stand for my ant plants, succulents, orchids, and a few tropicals.  I am pleased overall with the LED lights, but it is apparent that I need to make some adjustments where I place my plants and how much light they need to receive for optimal growth.  I tried using a lux meter without noticeable success and then I came upon a series of articles on PAR and PPFD that were published in Orchids Magazine in 2021. 

One of the biggest surprises in these articles is that amounts of light are now quoted in moles (mols) for horticultural purposes.  I'm used to the concept of moles in chemistry, but I had never encountered it in regards to lighting. The use of Avogadro's number (6.022 x 1023) to quantify photons was a new concept to me.  This advance coupled with the development of sensors that can quantify the photons in the photosynthetically active regions (PAR) of the electromagnetic spectrum and then give you a readout on a PAR meter in µmols per square meter appear to me to be a real advance in understanding.  These articles are written in such a way that a both technical specialists and a laymen can gain much useful knowledge about using some of these advanced techniques to better understand artificial lighting for plants. 

The author makes a convincing and evidence based case for using a PAR meter (Photosynthetic Active Radiation) to adjust the PPFD (Photosynthetic Photon Flux Density) for the type of plant you are growing.  Apparently, some LED fixtures available today are even dimmable.  PAR meters are pricey, but you get exact information that you can use and you don't have to guess how much red or blue light you need, what is the exact Kelvin rating of the lights you have, endlessly adjust the height of the shelves for your plants, or how much time your lights should be on.

I am researching PAR meters now and I hope to purchase one in the near future.  PAR meters with an actual full spectrum quantum sensor are expensive.  And many PAR meters on the market appear to have a lux sensor that takes a reading and then computes its output in PAR.  So it will take some time to sort through the various instruments on the market.  If anyone owns a PAR meter, would you please comment on the type you are using and whether or not you are satisfied with it?  Finally, I have a feeling that my plants might benefit from using full spectrum LED lights in the future, but I won’t know for certain until I try a PAR meter to see if I can replicate the results presented in the Orchids Magazine articles.

If you are interested in learning more about PAR and PPFD, you can obtain copies of these articles by asking your local public library to provide you with a pdf copy. After you obtain your copy, you can combine them into one file with a pdf editor.  Free pdf editors are available online. The final document will be about 12 pages long with a file size of approximately 18 MB.

2021/07 July ORCHIDS Magazine
·An Introduction to PAR and PPFD - Why You Should Forget Lumens: Part 1 of a Five Part Series on Light
2021/08 August ORCHIDS Magazine
·Let There Be Light! - Target PPFD for Orchids and Tropical Plants: Part 2
2021/09 September ORCHIDS Magazine
·Let There be Light - Part 3: Measuring Artificial Light Without a Quantum PAR Meter
2021/10 October ORCHIDS Magazine
·Let There Be Light - Part 4: Setting up Your LED Lights
2021/11 November ORCHIDS Magazine
·Let There be Light - Part 5: Spectrum and Photoperiod


Good luck and good growing.

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