Japan: Study finds cherry tomatoes more robust when grown under blue-hued LEDs

Scientists evaluated cherry tomato seedlings grown under dysprosium lamps and six light-emitting diode light treatments. Compared to the control, net leaf photosynthesis was increased significantly under blue, red and blue, and red, blue, green light and reduced under red, orange, and green treatments. Leaf thickness and length of palisade tissue cells significantly increased under blue, red and blue, and red, blue, green lights. Results suggested blue light is essential for growth of cherry tomato plants.

To meet worldwide consumer demand, tomatoes and other crops are often grown in greenhouses under electric lights. A move toward the use of light-emitting diode (LED) lights in greenhouses has led horticulturists to study the effects of these artificial light sources on a variety of greenhouse crops, including tomatoes. Understanding how light quality influences plant cell and tissue growth, photosynthetic characteristics, yield, and a range of other important characteristics is critical to high-production greenhouse operations.

Researchers from China and Japan offer new research that clarifies tomato plants' light preferences. The team investigated the effects of using dysprosium lamps (white light) compared to six LED light treatments. The study, published in HortScience, contains important details for growers.

The experiments used six LED treatments: red (R), blue (B), orange (O), green (G), red and blue (RB), and red, blue and green (RBG). All treatments were compared to the control, lighting from high-intensity gas dysprosium lamps, which the authors describe as a new type of metal halide lamp with a spectrum similar to the solar spectrum. Cherry tomato plants were subjected to the different light treatments for 30 days.

Compared with the control, net photosynthesis of cherry tomato leaves was increased significantly under the blue light treatments and reduced under red, orange, and green lights. Chloroplasts under R, O, and G showed obvious dysplasia, particularly those exposed to orange light.

"Palisade tissue cells in leaves under RB were especially well-developed and spongy tissue cells under the same treatment were localized in an orderly fashion. However, palisade and spongy tissue cells in leaves under R, O, and G were dysplastic. Stomatal numbers per square millimeter were significantly increased under B, RB, and RBG," the scientists said.

The team said their results show that blue light is essential for growing healthy

The complete study and abstract are available on the ASHS HortScience electronic journal web site: http://hortsci.ashspublications.org/cgi/content/abstract/46/2/217