Experiment: Red Light vs Blue Light -How Spectrums Affect Plant Growth- LED vs CFL

Blue light vs Traffic signal. Which is much better for vegetative development??? Intuitively, the answer might appear apparent: Blue light is for vege! That fundamental mantra has been plastered all over the internet. But if the issue was so basic, then why is it that so many LED grow lights are sold utilizing such a large ratio of red to blue? Why don't we see many pure blue "vege" lights?

Wouldn't nurseries that are growing seedlings want all blue LEDs? Would not indoor lettuce farms choose all blue light given that they don't want their lettuce to blossom (bolt)? Are horticulture LEDs high in traffic signal due to the fact that the majority of the artificial lighting market is targeting weed growers who desire marijuana producing enormous buds?


I decided to stop making presumptions and to evaluate this for myself! Specifically, today's experiment evaluates the following HYPOTHESIS: Blue light fuels vegetative development. Hence lettuce plants grown in the lack of blue light will grow slowly and develop less plant mass than lettuce grown under blue light.

I established a number of grow chambers using 4 kinds of artificial lights: Full Spectrum 6500k CFL, Pure Blue 450-460nm LED, Red/Blue 460 +630 +660 nm LED and Pure Red 620-630nm LED. One hydroponic (Kratky's Approach) lettuce was positioned under each light.

1:44 – Lights Specifications for This Test
2:14 – Specs for Hydroponic Service
7:27 – Results of Lettuce Development
8:03 – Photosynthetic Absorption Spectrum
8:10 – Photosynthetically Active Radiation (PAR).
10:53 – Suggested Light Levels for Lettuce.
12:02 – PPFD Light Readings for the Lights.

My Apogee Instruments PPFD Meter (# CommissionsEarned):.


It ends up that red light had the ability to grow just as much plant mass as the blue light. An included advantage to the red LED light was that it created simply as much PAR light, while taking in 29% less electrical power.

The traffic signal might have produced a large plant, but the quality of the plant was not desirable. The stem and leaf growth was very extended. It resembled a lettuce plant that is bolting. The leaves were pale, showing low chlorophyll levels. They were really weak, easily separating from the stem.

The blue LED showed comparable dry weight as the red, but it had higher chlorophyll levels, showing a much greener color and more powerful tissues. Development was still unfavorable though, as the plant stretched vertically, instead of remaining compact. It might appear that light levels were too low, however the PPFD PAR numbers were in fact expensive. Also, the blue light did not create as much root mass.

Examine these sources for suitable PPFD levels for lettuce:.

The Red/ Blue LED resulted in a more natural, compact development pattern. It would appear that the lettuce plants require a mixed ratio of reds and blue in order trigger a compact development attribute.


Many growers will focus on chlorophyll A + B adsorption charts, presuming that other wavelengths of light are useless to plants. However, PAR (Photosynthetically Active Radiation) covers the entire range of light in between 400nm and 700nm. All of this light can fuel photosynthesis with varying degrees of efficiency. In addition, photosynthesis is not the only issue of a grower.


We likewise should account for photomorphogenesis, which deals with the way plants grow in response to various wavelengths of light. This can even include wavelengths beyond the world of PAR, such as UV light. Plants will display various morphologies or developmental qualities in reaction to mixes of light. A timeless example is the ratio of red to far traffic signal.

In this test, we saw that consisting of blue light at a ratio of 1:3 (blue to red) had the ability to prevent the plant from growing in a lengthened style. This photomorphogenic reaction discusses why we see the popular red/ blue mix of LEDs that are so common in grow lights.


Complete spectrum light is the very best way to make sure that plants are getting whatever they require. However producing such light in LEDs can decrease effectiveness. Red and blue LEDs are the colors that offer highest levels of efficacy. Their light is easily absorbable by chlorophyll and quickly drives photosynthesis. In a proper ratio of blue to red, many plants react with natural looking growth.

What about thumbs-up? Do plants use green light, or it squandered energy?
Find out at my website:.

#ScienceExperiments #LEDGrowLights #VegetativeGrowth #IndoorGrowing #ArtificialLightings #HydroponicLettuce #UrbanGardening.

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