Abstract
Seedlings of a few tree species were grown under lights of different spectral compositions, using both natural and artificial light sources. The growth response of pine (Pinus thunbergii) seedlings to light quality was nearly the same for different tem-perature conditions or daylengths. In the blue box, where red light was reduced, their growth in height was greatly promoted, but dry matter production was greatly limited. Therefore, dry weight per unit axis length was remarkably less than under other filtered lights. Birch (Betula ermani var. communis) seedlings responded differently to light quality according to daylength. Under a longer daylength, their height growth was promoted under the light filtered through blue box. Under short daylength, however, it was pro-moted in the yellow box. The promotion was emphasized under a certain temperature condition. Todo-fir (Abies sachalinensis) seedlings seem to behave nearly in the same way as pine seedlings, but no primary needles or epicotyl growth were observed in most of them under 8 hour daylength. There is a possibility that terminal bud formation varies with light quality under longer daylength. In Cryptomeria, 1-0 seedlings were grown in different boxes. Their height growth was the largest in the blue box, but number of buds was greater in the yellow or red box.
