부산대학교 도서관

The effect of additional far-red (FR) irradiation produced by FR fluorescent lamps on the growth of lettuce (Lactuca sativa L. cv. Okayama) was examined. The main lighting source was 3-band fluorescent lamps. The photosynthetic photon flux density (PPFD) (400-700 nm) was kept at 200μmol⋅m-2⋅sec-1 in all treatments and each additional photon flux density (PFD) of FR (700-800 nm) irradiation in four treatments was kept at 107.1, 50.1, 25.6, and 9.3μmol⋅m-2⋅sec-1, respectively. The experiment was performed in a controlled environment at 25°C and at 70% relative humidity.According to the level of additional FR irradiation, the fresh weight, dry weight, leaf area, stem length and internode length of the lettuce was increased. Although the PPFD remained constant, additional FR irradiation was useful in accelerating plant growth. It was believed that plant photomorphogenesis was changed by FR irradiation, resulting in the increase in the internode length and leaf area and cosequently the plants were able to absorb more photons.Comparing the two methods of accelerating plant growth, adding FR irradiation and increasing the level of the PPFD, the former was more efficient than the latter as far as electrical consumption.