PLANT PRODUCTION IN THE ARTIFICIAL ENVIRONMENT
The growth response of butterhead lettuce to HPS and MH has been compared. Comparisons were made at equal photosynthetic photon flux (PPF) of 350 μmol m-2 s-1 under a 12 h light and 12 h dark photoperiod.
Preliminary results indicate that the growth of lettuce was fairly good under both HPS and MH. The required growth period from sowing for a 100 g fresh head weight plant was reduced to 27 days. There were no significant differences in fresh weight, dry weight and leaf area between the lettuce plants grown under HPS and MH. However, the leaf number of the plants grown under HPS was greater than that under MH, and slightly longer and wider leaves were obtained under MH than under HPS. The results indicate that the spectral power distribution of radiation from lamps has a morphological influence on the growth of lettuce, but has no influence on fresh or dry production at the range of PPF applied in this investigation.