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Booster LEDs Take Plant Steering to a Whole New Level

(An abridged version is found in the January 2011 issue of Maximum Yield.)

LEDs have made significant progress in the past few years, and their impact on the horticulture lighting industry has been huge. Not only are they energy saving and long lasting, their innate ability to produce wavelength specific light makes them perfect for growing plants, which respond to certain parts of the light spectrum. Low heat emission from LEDs also gives growers the opportunity to place more lights over their plants to help boost performance.

The advancement of Dense Matrix LED technology is allowing growers to do more with their plants than ever before. This platform provides the intensity plants need for photosynthesis, penetrating deep into the leaves of the plants. With its highly focused beam, growers can also direct light to specific dark areas. From isolating and mixing select wavelengths to increasing light intensity by closing the proximity of the light to plants, these spectrum specific, low heat emitting LED lights are becoming versatile in their uses. Growers that have made the move to LEDs have been very successful in their growing ventures.

Booster LEDs

Even growers who haven't had the opportunity to transition to LEDs can experience their benefits. Because these lights are so small and versatile, growers can use LEDs to control their plants as a booster or supplement to their already existing light systems. During the various phases of growth, plants vary in response to different spectrums. Studies have shown that more blue light can enhance vegetation, while red light boosts flowering and fruiting. Traditional broadband sources only come in limited spectrums that cannot be optimized for all stages of growth. By increasing the quantity of a specific wavelength or spectra the grower can manipulate crops to express improved growth and yield. Specifically, by adding the amount of blue light the grower can prolong vegetation or increase the rate of vegetative growth. Increasing the amount of red light can promote flowering in plants and increase fruit production.

Dense Matrix LED technology offers promising results when used in conjunction with conventional lighting. By packing LED chips closely together, it not only creates a bright, point source, it shrinks the size of the actual unit. This compact form factor adds the desired spectrums without blocking light from traditional sources. Multiple mounting options add to its versatility—individual LED lights can hang directly from the ceiling, or be directed to a specific area by a gooseneck arm. Growers also don't have to worry about added heat in their grow tents; the traditional grow light systems are hot enough! With its expertly designed heat management system, lights using Dense Matrix LED technology run cool. Delivering intense light while radiating very little heat makes these grow lights ideal as a booster, as no further venting systems are needed. This platform is providing a whole new dimension to plant steering.

Traditional lighting systems usually implement broadband sources such as metal halide, high pressure sodium, and T5 fluorescent lamps. Often used for seeding, T5's need the added blue spectrum to enhance performance in the vegetative phase and red to boost fruiting and flowering. Other growers use metal halides during the vegetative phase of a plant's growth because of its higher blue spectrum emission. However, during the flowering phase, they have to swap out the metal halide, or suffer poor results during fruiting.

With LED boosters, growers no longer have to buy another system—they can just supplement the missing but favored red spectrum for flowering with a red LED light. The same is true for high pressure sodium lamps, which are high in red spectrum production. A blue LED booster can be supplemented to help the vegetative performance of the plant. The benefit of implementing LED boosters is that instead of moving plants from tent to tent or swapping out lights, growers can keep their existing broadband lighting but generate the same great results.

Experiment #1: Red Booster for Flower and Fruit Promotion

We conducted a couple of experiments to see how well LED booster lights would perform and see the effect of different spectrums.

For the first experiment, we wanted to see the behavior of tomato plants under different boosters. We started twelve Juliet Hybrid tomatoes from seed and grown to seedlings beneath an eight bulb, T5, fluorescent hood. At this point, three LED booster lights of different wavelengths and spectra were introduced. We selected three LED units, red, blue, and magenta, that were then placed directly above three separate tomatoes at one side of the grow area. This enabled us to concentrate the alteration of the fluorescent light spectrum. (No partitions were imposed upon the samples, allowing potential for influence upon the growth of adjacent nine plants.) The initial vegetative growth of these seedlings into full size tomatoes and proceeding reproductive growth were analyzed and compared to those tomatoes farthest from the influence of the LED boosters, which served as the control group for this experiment.

The results from this initial LED booster experiment demonstrate that the addition of a red LED booster to an eight bulb T5 fluorescent hood encourages fruit production and fruit ripening. During initial vegetative stages, three to five weeks after transplant we observed a noteworthy increase in growth occurring in the tomato plants under the red and magenta LED boosters. However, as the experiment advanced, the other tomato plants grew to be larger in size but produced few flowers and no fruit. Ultimately fruit production and maturation was limited exclusively to the quadrant of the treatment that included to the red booster.

Experiment #2: Blue Booster for Vegetative Growth Improvement

Where red LED boosters shift full spectrum lighting treatments toward a flower and fruit-promoting spectrum, blue LED boosters serve to improve the spectrum for vegetative growth under unequal color emitting lighting systems. When a blue spectrum is used in combination with a high pressure sodium bulb, improve vegetative growth by decreasing internode stretching, eliminating the yellow chlorotic appearance of leaves, and increasing stem width and branching. To test this, we conducted a separate experiment with only a blue booster over tomato plants.

Two separate treatment groups of Gardener's Delight tomatoes were grown beneath an eight-bulb T5 fluorescent hood. One included tomatoes beneath two suspended blue units and the overhead HPS hood. The other group as the control for this experiment, grew exclusively under the HPS bulb. The tomatoes under the blue LED unit expressed darker color leaves, thicker stems, and increased branching. Internode length was shorter and leaf number was higher among these tomatoes. Flowering occurred in these tomatoes more rapidly and flower number was greater. Results were exaggerated by week three to four of growth, demonstrating that the tomatoes grown under an HPS hood with blue LED boosters clearly outperformed tomatoes grown exclusively under an HPS treatment during the vegetative stage.

Not Just Any LED

From these experiments, the effectiveness of using supplemental LEDs to manipulate plant growth is evident. However, not just any red or blue LED booster can produce the same effects. We picked out specific combinations of wavelengths that we had tested against others with varying effects. In one of these experiments, there was a commonly used blend of red wavelengths that had adverse effects to crop yield and fruit ripening. With our tailored mix of red wavelengths, the tomato plants were able to responded favorably during the flowering and fruiting period in the experiment with the T5 fluorescent lamp. In the same way, our formula of blue wavelengths strengthened the plants' vegetative growth by supplementing the high pressure sodium light. Without the added spectrum from these LEDs, the broadband sources could not have produced such results.

The convenience and ease of installing LED booster lights gives growers more flexibility to grow in ways they couldn't before. Indoor gardeners can now steer their plants by implementing optimized blue wavelengths for stronger plants and red wavelengths for higher yields. Compact, low heat, and powerfully bright, Dense Matrix LED technology has paved the way for a spectral revolution!