Ascorbic acid improves conversion of white spruce somatic embryos

The effects of exogenous applications of ascorbic acid on white spruce somatic embryogenesis were examined. Increasing concentrations of ascorbate (1 μM to 100 μM) in the germination medium enhanced somatic embryo conversion in a linear fashion. At the optimal ascorbate level (100 μM) the number of embryos able to undergo normal conversion, i.e., emergence of both root and shoot, increased from 34% (control) to 58%. The effect of ascorbate had a more pronounced effect on shoot growth than on root emergence; and at 100 μM ascorbate, the percentage of embryos able to produce new leaf primordia increased from 47% (control) to 79%. Root emergence increased slightly from 64% in the control embryos to 74% in the presence of ascorbic acid. The ascorbate-treated embryos were characterized by an enlarged apical region, presumably due to a larger number of leaf primordia produced, and by dark green leaves. When allowed to grow further, these embryos were able to develop into normal plantlets.