Abstract
1. Blue light treatment using blue film over the plants in the nursery stage increased both the number of tillers and the top dry weight 37 days after transplanting, while red light slightly stimulated the formation of tillers. 2. Under solar radiation of 403 cal·cm-2·day-1 during the nursery stage, the highest increase in growth during the early stage after transplanting was obtained when the transmission rate in the visible region was 60% and B/R ratio, as expressed by the relative value of transmission energy in the 400-500 nm region to that in the 600-700 nm region, was 2.33. Because in some years solar radiation becomes lower, it is desirable to have films to cover plants whose transmission rates are as high as 70% and to make the B/R ratio as high as possible in the range from 1.78 to 2.33. 3. For the purpose of promoting growth during the early stage after transplanting, nitrogen content of the tops needs to remain balanced with the ratio of top dry weight to plant height. The seedlings grown under blue light were seen to have such a desirable balance. 4. Not only in the standard raising system (germinating-greening-hardening), but also in the omission system with germinating and hardening only, blue light had a good effect on the growth after transplanting. In the omission system, the effect of blue light was much enhanced when the period of promoting germination was prolonged to 3 or 4 days.
