Light sources fluorescent bulbs

Sherer Environmental Chambers models CEL-512-37 and CEL-34-14 were freshly outfitted with incandescent (93W) and cool white VHO fluorescent bulbs. Eleven plants from each of the three sources were divided between the two chambers. Plant-top light-intensity varied from 2,800-3,300 ft-c, depending on plant height and the chamber involved. Controls were set for maximum relative humidity (measurements varied between 50 and 100%). Temperature was set at 22°C day (16H) and 17°C night (8 H). Plants were grown under these conditions for 12 wk. Beginning 24 Jan 1980, daylength was decreased from 16 to 11 h over a 4 wk period. 

Weatherabilities of flexible PVC sheets were compared by exposing samples in a fluorescent light apparatus for UV exposure (ASTM G 154) for up to 5000 hours. Light source was either a UVB (nominal peak irradiance at 313 nm) bulb or a UVA bulb (nominal peak irradiance at 340 nm). Light source irradiance at 313 nm was 0.7 watts/m /nm and at 340 nm was 1.55 watts/m /nm. Operating cycle was 6 hours dry at 70°C and 6 hours wet at 50°C. 

---