SODIUM LAMPS FOR GROWING ROOMS

Low-pressure sodium (LPS) lamps are the most efficient commercially-available sources for the production of light but their use in growing rooms for raising young plants in the absence of daylight is restricted because the more important crop plants – tomato and lettuce-develop abnormally in LPS light alone.
Earlier work has shown that this abnormality can be prevented by substituting radiation from blue tubular fluorescent lamps for a proportion of the LPS radiation.

This paper gives the results of experiments with young lettuce plants to determine the effectiveness of other sources of blue light, in the form of warm white tubular fluorescent lamps and two types of metal halide lamps, for achieving the same purpose.
These indicated that a considerably higher proportion of warm white radiation is needed compared with blue, that the normal metal halide lamp is less effective but that between 10 and 20 per cent of the total irradiance in the form of light from an Indium halide lamp produced favourable results.
Higher proportions were less effective.

The dependence of the response on irradiance was also demonstrated.

II International Symposium on Artificial Light in Horticulture

A.E. Canham

https://doi.org/10.17660/ActaHortic.1982.128.19