Secrets of Photosynthesis!

Home / About Grows / Secrets of Photosynthesis!

Secrets of Photosynthesis!

If we want to measure the amount of effective light an LED, HID or fluorescent light fixture emits for a plant to use, there are things we have to examine.


If we want to measure the amount of effective light an LED, HID or fluorescent light fixture emits for a plant to use, there are things we have to examine.

One of these is PAR, or Photosynthetic Active Radiation. PAR is essentially a measurement of light emission within the photosynthetic range of 400-700 nm. This represents the area of light that plants use for photosynthesis, or to grow. PAR is measured by the amount of micro moles of light per square meter per second. Although PAR is a key instrument, it only tells one part of the story. There are many areas within the PAR scale which plants absorb only in small quantities, such as in the green range (560 nm). Thus, a reading of a light’s spectrum must be used in conjunction with the PAR reading to determine from what bandwidths those micromoles are being generated, and in what amounts. A spectrum reading is obtained by using a piece of equipment called a spectrometer. These two readings together will give a complete picture of a light’s effectiveness; PAR showing strength, and spectrum showing that this strength is in the proper wavelength proportion for what the plant can actually utilize, and not just wasted energy. These two measurement tools produce a reading that shows not only what wavelength or color is being emitted, but also the absorption value of that particular wavelength. By looking at this graph, one can determine if the light is emitting the proper wavelengths used by the plant for photosynthesis and at the correct absorption peaks required for robust and quality plant growth. HID lights are a classic example for why considering both of these readings is so important. These traditional lights have decent PAR readings, but when their spectrum is revealed, it becomes evident that they emit most of their energy in the wrong areas, making then an inefficient lighting option. Our LED lights, on the other hand, compared to HID lights, as well as to other LED lighting options, show extremely high PAR readings with an efficient and accurate distribution of strength across your plants’ desired spectrum.

PAR Reading Comparison at Various Footprint Intervals


Measurement taken at height of 60 cm.

LED Light Spectrum at 60 cm

with Plant Absorption Percentage by Nanometer Overlay

What is the situation in the case of the white LED lights?

Our LEDs have been designed to have full yet targeted spectrum for growth and/or flowering, and don’t waste any energy emitting large amounts of spectral ranges that plants don’t use high amounts of. We specifically target the areas with the highest absorption rates in order to deliver exactly what the plant needs for photosynthesis, and not a bunch of light the plant otherwise sees as useless.

A lot of manufacturers use all white LEDs in their design. These lights follow the more familiar color temperate range that we commonly know from HID and T-5 bulbs, 2700K-6500K. Although this makes a light that is closer to what we are all used to seeing as far as color, it negates one of the most important benefits of LED lights, not wasting energy on light the plant can’t really absorb and use.

A few manufacturers are touting that they have replicated the spectrum of the sun. That’s great and all, but the big difference between the sun and your grow light is that the sun is an endless supply of nuclear energy, so it’s not that concerned with expelling energy in those lesser used spectral ranges, plus those colors mixed together make the world a beautiful place. Your grow light and wallet on the other hand, would rather not waste unusable energy and your plants could care less if they aren’t seeing the world in real color. In fact, they’ll thank you for the purple world they grow in because they know that you’re doing your part to conserve for the planet, while giving them what they need to succeed.

(HPS lamps use various gases, like sodium, mercury and xenon. Sodium by itself produces a mostly yellow spectrum range, which is why HPS are extremely heavy in this range of wasted light. HPS bulbs also have a limited blue range, for which mercury is responsible)

No posts were found