LED PAR SPECTRUMS

If you still wish to consider LED lights because the manufacturer claims they make lights which are better tailored for plant growth. They'll claim their LED lights are 20 times better than conventional grow lights. Or that LED will deliver the narrow and exact spectrums for maximum PAR for plant lighting. No wasted spectral energy. Then we really need you to understand about how an LED interacts with your plants both photosynthetically and during Photomorphogenesis.

Let's take a look at some of the LED manufacturers claim that the advanced technological advantages of using LED over a traditional HPS for flowering and bud is a result of the LED lamp arrays delivering the narrow maximum PAR absorption spikes for chlorophyll A (430-670 nanometers) and chlorophyll B (450-640 nanometers) that the traditional HPS does not.

If you were to just take the LED manufacturers spectral analysis at face value you would see that the LED lamp they designed for this stage growth does fall within the ranges of the CHLOROPHYLL ABSORPTION CHARTS. So while it is true that LED lamps can provide the specific concentration wavelengths (650-670 nm) of that of a traditional HPS grow light, the manufacturers use of this as evidence that it is this narrow spectrum which the LED emits as critical for plant growth is at best sporadic and tends to be mentioned only when it's in the commercial advantage of the proponent.

But there is a problem with the claimed advantages of narrow spectral emissions during the plants later stages and those of you who have experimented with LED lamps have encountered them. It's actually a result of the narrow LED spectral properties that plants experience Photo-inhibition which contradicts the specific concentration wavelength advantages of the LED grow lamp.

Studies such as the Emerson Effect have shown that a wider spectrum lamp for this growth stage, such as an HPS lamp, does emit a broader spectrum and the plants will take full photochemical advantage of the photosynthetic and Photomorphogenesis processes from the traditional HPS source that are not available to them under the narrow spectrum LED grow light.

The other problem for the LED manufacturers when only relying solely on the chlorophyll absorption charts are that they are levels set for isolated chlorophyll molecules suspended in a solvent and do not reflect total photosynthetic activity. Even within the Chlorophyll Absorption Charts different solvents will give slightly different numbers.

So what the grower would really want to know would be the NET PHOTOSYNTHESIS or Action Spectra of the plant receptors by the light source. When you refer to LAND PLANT ACTION SPECTRA (Algae Action Spectra charts are different) you'll see the relative results and not absolute absorption values. These values are considered normalized so that the lighting spectrum that is most efficient in photosynthesis is at 100% for that plant species. This does not mean that 100% of that lighting spectrum is used in photosynthesis. It is only 100% compared to other lighting spectrum.

LED manufacturers who rely solely on Chlorophyll Absorption Chart and don't reference Net Photosynthesis Action Spectra data or accept the Emerson Effect do so because it's not in their best commercial interest to do so.

LED DISTRIBUTION VS INDUCTION

LED lamps are highly directional with vertical beam spreads between15 – 50°. To illustrate the intensity of the LED one need only look directly into an LED or as you see LED sign on the side of a freeway at night, how long did it take you to recover your full vision once you looked away from the LED source?

LED grow lamp plants also suffer from their narrow vertical beam spreads with lack of CANOPY PENETRATION. The angle of light at the plants is an important consideration since the rays of sunlight nearly parallel by the time they reach an outdoor plant due to the distance between earth and sun. This means that a 6 ft plant will be illuminated equally from top to bottom outdoors insuring dense growth and high yields. While not accomplished by nature of the LED design it is normal for an INDA-GRO Induction Grow Lamp to achieve canopy penetration of 30” and more.

PHOTOMETRICS is then how we refer the light distribution levels of any fixture/lamp combination. This is an important relationship because it will determine how much of an area a given fixture will light as it correlates to either visible distribution levels or plant lighting (PPF, YPF, PAR lp/w) values and the efficiency of the light source.

Proper lamp selection itself would be the first thing that determines the quantity of light energy reaching the plant but it's important that the levels being considered have been taken with the selected lamp and the fixture combined for what's referred to the IN SITU levels. In situ is a Latin phrase used in the lighting industry that stands for ‘in place'. In situ measurements are the only way to accurately measure in a surface point by point value how efficient the total lamp/fixture package will be to the customer.

In situ measurements will also depend on such factors as the housing materials and design, color, reflective materials and shape within the fixture, and lens design will all come together to perform in meeting your plants large area coverage needs. It's not unusual for identical lamp/ballast combinations to measure widely different In situ photometric values dependent upon how the manufacturer dealt with the design and materials quality of the fixture they developed.

Now let's look at how much PLANT LIGHTING will be needed and how that measurement is different than how we measure light for human vision.

One of the ways we measure the quantity of light reaching the plant is in the PHOTOSYNTHETIC PHOTON FLUX values. Let's take a look at a 100 watt LED lamp putting out lighting levels of roughly 100 umol/sec (mol is pronounced micro mole and describes the amount of photon packs striking a square meter every second). So just how far will that 100 umol/sec of light get you? Well, to put it into perspective, full sunlight is 2000 umol/meter^2/sec (2000 umol per square meter per second), the photo saturation point for many food crops is around 1000 umol/meter^2/sec and most food crops thrive at 500 umol/meter^2/sec especially in flowering. The answer for the 100 watt LED light at an intensity of 500 umol/meter^2/sec is roughly two square feet. So while the 100 watt LED lamp can definitely grow in a larger area the rate of photosynthesis will proportionally go down.

As the cost of electrical energy costs continue to rise, the commercial grower needs to have considered how the efficiencies of his grow lights when considering photometric In situ values, high power factor, low total harmonic distortion, and daylight harvesting control features can significantly reduce those monthly operational costs. Induction grow lights score well in all of these areas.

And while you might take from all this that we're entirely down on using LED lighting that is not entirely the case. We've found it worked well for clone and vegetive stages but for the customer to make a fully informed decision to use LED you need to know the lifetime operational and economic benefits of selecting LED for these processes. However we believe that once you remove the hype surrounding LED grow lights you'll choose our Inda-Gro Induction Grow Lights.

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