Equipment for Growing Plants in Nitrogen Fixation Studies

Abstract

1. Two types of equipment used in symbiotic nitrogen fixation and related studies are described. One of these consists of a shallow water bath, an overhead bank of lights, and the necessary accessory equipment for operation. The main features in which it differs from installations previously described are in discarding light filters and air conditioning devices for control of spectral balance and air temperatures, and in substituting mercury vapor lamps and a water bath. It was found that most plants will grow well at the highest air temperatures reached if the spectral balance is fairly good and the roots do not become too warm. The intensity of illumination secured is usually about 1500 to 2200 foot candles (16,100 to 21,500 lux). With 1000 watt lamps over 4000 foot candles (43,000 lux) has been attained. Most plants grow in a practically normal manner in the apparatus. 2. The second apparatus consists of a unit composed of a water jacketed glass culture chamber mounted by means of a rubber stopper in a wide mouthed Erlenmeyer flask which contains the material in which the roots grow. A number of such units are assembled in a tin plate housing to conserve the light. Good growth of small leaved plants under biologically controlled conditions is easy to secure with the apparatus.