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Tibor Tischner
Fluorescent Lamps Have Been Replaced by Metal Halide Lamps in the Martonvásár Phytotron Agricultural Research Institute of the Hungarian Academy of Sciences Martonvasar, Hungary Summary Twenty years ago, the light sources in the Martonvásár phytotron units consisted almost exclusively of fluorescent lamps. Developments in light sources are almost always aimed at improving conditions for human vision. It is now a well-known fact, however, that the requirements raised by plants as regards both the spectrum and intensity of the light are quite different from those required by the human eye. This means that lighting developments can rarely be applied in plant growth chambers, and then only by a lucky chance. The development of metal halide lamps for colour television purposes can be regarded as one such lucky chance. The fact that these light sources have a spectrum very similar to that of natural light and can be used to achieve high levels of illumination means that, in addition to their original purpose, they are also well able to satisfy the criteria to be met in plant raising. In the late seventies, extremely encouraging results were obtained when metal halide lamps with rare earth additives (dysprosium, holmium, etc.) were tested in the Martonvasár phytotron. Similarly favourable results were also reported from other phytotrons and green houses where plants were grown under metal halide lamps. As a consequence of this, when the Martonvásár phytotron was renovated in 1990, the fluorescent lamps were replaced by metal halide lamps in the vast majority of the plant growth units.
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