GROWTH AND HARDENING OF 4 PROVENANCES OF CONTAINERIZED WHITE SPRUCE (PICEA-GLAUCA (MOENCH) VOSS) SEEDLINGS IN RESPONSE TO THE DURATION OF 16 H LONG-NIGHT TREATMENTS

Long-night treatments of 16 h were applied to four provenances of 10-w eek-old Picea glauca (Moench) Voss seedlings for durations of 0 (contr ol), 4, 8, 12 and 16 d. Their effects on growth and on the development of frost hardiness were determined during the fall. Height growth ces sation was hastened by long-night treatments, with 4, 8, 12 and 16 d t reatment seedlings ceasing growth approximately 5, 10, 13 and 15 d ear lier than control seedlings. The rate of hardening was affected by the duration of the long-night treatment while the level of hardening was affected by both treatment duration and the latitude of origin of the seedlings. Specifically, seedlings receiving the 8, 12 and 16 d treat ments had achieved approximately the same level of hardiness by mid-Oc tober, which was greater than the 0 and 4 d treatments. However, hardi ness levels of the 12 and 16 d treatments were higher in late Septembe r than with the 8 d treatment. The level of frost hardiness in late No vember increased with both increasing duration of long-night treatment s (0 to 8 d) and increasing latitude of origin.