Growth and nutrient absorption by tomato seedlings in a growth chamber with prism light guides and electrodeless discharge lamps

• Published in: Acta horticulturae no. 580; pp. 203 - 206
• Main Authors: Higashide, T, Shimaji, H, Hamamoto, H, Shimazu, T, Honda, J, Hashimoto, M, Nakamura, K
• Format: Journal Article
• Language: English
• Published: International Society for Horticultural Science 01.01.2002
• Subjects: absorption; air; greenhouses; heat; lamps; seedling growth; seedlings; thermal radiation; tomatoes
• ISSN: 0567-7572
• DOI: 10.17660/ActaHortic.2002.580.26

We developed a lighting system that uses prism light guides and electrodeless discharge lamps and trialed this system in a plant growth chamber. A prism light guide is a type of hollow light guide shaped like a cylinder. The average light ray propagates mainly through air within the structure, guided by numerous optical interactions before leaving the structure. Because the luminous part of the lighting system is kept separate from the light source, less thermal radiation is received from the luminous part than would be received from the lamp directly. We investigated the growth of and nutrient absorption by tomato seedlings in a growth chamber fitted with the prism light-guide. We raised tomato seedlings hydroponically in the growth chamber, and compared them with those grown in another growth chamber under the currently favored metal halide lamps. In the latter chamber, the growth of plants receiving high photosynthetic photon flux was restricted by excessive heat. In the chamber with prism light guides, growth was not restricted, and growth rates were high. Moreover, the nutrient absorption levels of the plants that received high PPF in the chamber with prism light guides were not strikingly different from those of plants under metal halide lamps or in the greenhouse.