Effect of light intensity during extended photoperiod on growth of amabilis fir, mountain hemlock, and white and Engelmann spruce seedlings

Abstract

Abiesamabilis (Dougl.) Forbes, Tsugamertensiana (Bong.) Carr., Piceaglauca (Moench) Voss, and Piceaengelmannii Parry seedlings were grown in an outdoor container nursery using one high-pressure sodium vapor lamp to provide a 24-h photoperiod. Eight intensities of lighting were arranged, viz., 220, 80, 40, 20, 12, 8, 5, and 0 lx.Extending the photoperiod and increasing the light intensity had a significant positive effect on the length and weight of seedling shoots and delayed terminal bud set. Root growth response to these treatments was negative, although the differences were rarely significant. Seedlings grown under a light intensity of 220 lx were the largest. The minimum intensity required to produce seedling shoot lengths which were significantly larger than the controls was in the range 20–80 lx.