Effects of natural chilling and cold storage on budbreak and root growth potential of loblolly pine (Pinustaeda L.)

Abstract

One-year-old loblolly pine (Pinustaeda L.) seedlings of 20 open-pollinated families were lifted from the nursery on November 23, 1981, and January 18, 1982, after the accumulation of 207 and 734 chilling hours (0 °C ≤ temperature ≤ 8 °C), respectively. Seedlings were tested for bud dormancy (rest) intensity and root growth potential after lifting and after 500 h in cold storage. There was a twofold range in dormancy intensity of 20 families at 207 chilling hours. Bud dormancy intensity was reduced as rapidly in cold storage as in nature. At 1234 chilling hours (500 h of which were in storage), families did not significantly differ in dormancy intensity. Root growth potential was severely reduced by storage (500 h at 2–4 °C) of seedlings lifted on November 23. In contrast, root growth potential of similarly stored seedlings lifted January 18 either was unaltered or had improved in storage.