Ascorbic acid improves conversion of white spruce somatic embryos

The effects of exogenous applications of ascorbic acid on white spruce soma tic embryogenesis were examined. Increasing concentrations of ascorbate (1 mu M to 100 mu M) in the germination medium enhanced somatic embryo convers ion in a linear fashion. At the optimal ascorbate level (100 mu M) the numb er of embryos able to undergo normal conversion, i.e., emergence of both ro ot 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 mu M ascorbate, the percentage of embryos able to produce new leaf pri mordia increased from 47% (control) to 79%. Root emergence increased slight ly from 64% in the control embryos to 74% in the presence of ascorbic acid. The ascorbate-treated embryos were characterized by an enlarged apical reg ion, presumably due to a larger number of leaf primordia produced, and by d ark green leaves. When allowed to grow further, these embryos were able to develop into normal plantlets.