Comparative Growth of Birch Seedlings Grown in the Greenhouse and Growth Chamber1,4

Abstract

Abstract The growth of paper birch (Betula papyrifera Marsh.) seedlings was greatly accelerated by high light intensity applied in a growth chamber at the cotyledon stage and continued for the next 8 weeks. At the end of the 8-week period, seedlings grown in a growth chamber under 2500 ft-c (26.9 klx) of cool-white fluorescent and supplemental incandescent light, a 16-hour photoperiod, and 25/18°C day/night temperature weighed over 40 times more than those grown in the greenhouse under natural daylight supplemented by 200 ft-c (2.16 klx) of cool-white fluorescent light, a 16-hour photoperiod, and 24/18°C day/night temperature. Compared with plants grown under low light intensity, plants grown for 8 weeks under high light intensity were 6 times taller, had twice as many leaves, and produced lateral shoots containing 17 times as much dry matter. These findings indicate the feasibility of using high light intensity alone at the seedling stage in the commercial production of planting stock of this species.