Abscisic acid concentration in Douglas-fir needles in relation to lifting date, cold storage, and postplanting vigor of seedlings

Spring-lifted seedlings were grown in pots in the field and, after a natural fall photoperiod, exposed to three 25-day cold (+4 °C) storage treatments and two lifting times, mid-November and mid-January. The storage treatments were light storage in pots, dark storage in pots, and bareroot storage in polyethylene bags in the dark. In a second experiment, an extended fall photoperiod treatment was applied to seedlings that were then stored in pots and subjected to the same light and dark treatments above. In both experiments, needle samples were taken four times during and after the treatments for abscisic acid assay. Abscisic acid concentrations were determined using gas liquid chromatography after purification with high performance liquid chromatography. Lifting times and storage treatments did not result in statistically significant differences in abscisic acid concentrations. However, there were treatment differences in characteristics of postplanting performance. Mid-November lifting resulted in reduced survival and a greater number of days to bud flush compared with the mid-January lifting results. The extended fall photoperiod material produced similar results to the natural fall photoperiod material. The failure to detect a relationship between needle abscisic acid concentration and seedling vigor may have been due to a transitory role of abscisic acid in the storage conditions studied. The quantification method for abscisic acid is insensitive and laborious for practical seedling testing.