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Compact Fluorescent Light - Part Three By Jerry Meislik |
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Introduction In 2007 I did two experiments comparing a commercially available LED grow light bar to a fluorescent four tube light fixture. (Click here to read Article 1 and Article 2). In the previous tests the LED grow light performed poorly and did not result in healthy growth of either vegetable seedlings or of Ficus virens. Recently I was contacted by Roman Kolesnikov and Jon Faix to consider trying a unique LED array that they have specifically created to grow plants. In a note from Roman: “My name is Roman Kolesnikov. I am a developer mostly work on developing embedded electronics and communication systems. I spend part of my time on fun projects, and have a group of grad school friends working along. Our fun projects are mostly focused on things interested to us. For the past four or so years, we have been isolating the chlorophyll type I and II and III reactive response. We use filters and cold laser technology to excite tissue on a petri dish. The problem with commercial LED lights, is that the makers use commercially available LEDs. These are not very good for the organic growth. I am interested in providing you with a custom piece to use on bonsai trees. We know how to limit chlorophyll to dwarf the plant. The plant would be very healthy, but appear something of a tundra based size (smaller and not energetic in development). We have done similar tests mostly on fly traps and other plants. I work with a partner Jon Faix on this project, and we are interested in utilizing you as an independent tester. Our device would be focused on dwarf but very healthy growth. I am very interested in your tests, as we have some very interesting ideas specifically about the bonsai trees.”
Experiment
My experiment was started 5/18/09 and completed 7/1/2009 for about 6 weeks. The LED panel provided by Roman and Jon was tested against a single spiral compact fluorescent of 13 watts. The fluorescent bulb was just a normal bulb and not a special plant grow bulb. Both the LED and the fluorescent lights were suspended about 5" above the tops of two pots of Ficus virens - totaling about 3 or 4 plants under each light. I grew the plant material, Ficus virens, from seed meaning that their character can vary a bit. Ideally the experiment would use one clone of plants so their intrinsic genetic nature and responses would be identical. However, with several plants in each test group we should have a reasonably accurate idea of how this material responds to the lights. The plants were about two and a half years of age and growing in small plastic cups (with drain holes). The cups were filled with soil composed of red lava and some bark chips. Fertilization and watering was done as needed.* Particularly interesting is that watering is reduced due to lack of heat by the LED and fluorescent lights as compared to growing under metal halide lights. Watering generally was needed every 2-3 days at ambient room temperatures of 65-70F. When the test was started the plants were about 5-6“ tall. Prior to the test the plants had been cut back several times, creating typical bushy plants suitable for further bonsai training. Both lights were set on a clock timer to provide for an 18 hour day. The LED panel, is a plastic circuit board mounted on one side with LED’s, connected to a transformer that provides the proper voltage. The LED panel has an array of blue and red bulbs. There are 66 bulbs in total with 25 red and 41 blue LEDs. Some of the blue bulbs appear brighter to my eye than others. Each group of blue bulbs and red bulbs has a switch that allows either or both colors to be on. For this experiment I made the decision to leave both the red and blue bulbs on. Additional information from John and Roman: “The panel you have operates three different light sources operating at .375 watts each. Roughly you have about 1.2 watts total. The light systems are mostly designed to promote lush dense vibrant foliage and thick robust stems/branches. In other words it's more for promoting lateral growth and overall health and vibrancy of a plant, and while some vertical growth will occur it wasn't the primary goal that Roman and I had in mind. My opinion is to use them on relatively established plants, or those you want to 'flush out' a bit, but I should mention that even though the primary goal isn't for vertical growth, if you keep the red LEDs running the vertical growth should at least match that of any number or arrangement of fluorescent bulbs. If you find good results with this panel on a bonsai tree, we could have an existing company manufacture a specific configuration just for that purpose. In the past we had made such a run with germinating equipment. Neither Jon or I make any money on these trials, and we do it for pure fun (at least so far). I think that an individual section ( like yours) could be made available for $20 or so. Your panel is a bit overkill. The abundance of blue would not hurt, but I have a tangerine tree thriving just under 8 diodes. The power 1.2 Watts is the total power consumed by your lights in your test panel. There is some overhead in converting 110AC to 9V DC and some resistors may also add 5 to 10% overhead. However, that loss is also not stated on other bulbs. I don't recall the ratio between the two blue variations, as we used different blue sources to trigger different photosystems.”
Results At six weeks I inspected the plants in each group and also informally queried three others about their impressions. Plants were inspected for: 1. Stem: elongation, thickness, vertical and lateral growth/branching 2. Leaves: growth – number of new leaves, texture, thickness, color Conclusions The LED panel performed well with no evidence of light toxicity as was the case with the LED grow light that I used in the first two studies. Overall, the plants under the fluorescent light performed better than under the LED light panel. In general the fluorescent grown plants showed better leaf texture and leaf color as well as more growth apically and laterally. Stems were also a bit sturdier under the fluorescent bulb. These differences are not huge but I believe significant. The LED panel uses much less electric current and is likely to run for more years than the fluorescent bulb. On the downside it also probably would cost more to produce (if it were in commercial production). I think that LED illumination may well be the wave of the future for indoor plant growth; further work needs to be done to fine tune the power and spectrum of LED illumination to tailor it for optimum plant growth. In addition, selecting specific wavelengths of LED's may allow tailoring of the light spectrum to be especially useful with bonsai by keeping plants growing laterally rather than apically as well as increasing the branch density needed for the look of a mature bonsai. Thanks to Jon and Roman for providing the LED panel and for their background information on LED’s and chlorophyll.
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