Improved Adventitious Shoot Production in White Ash
To increase adventitious shoot formation, we investigated the effects of the number of weeks on medium with high levels of plant growth regulators and seedcoat removal. Dissected white ash seeds were placed on a solidified MS medium containing 10 μM TDZ and 1 μM 2,4-D (shoot initiation medium). After 2, 3, or 4 weeks in vitro, explants were transferred to shoot elongation medium (3 μM TDZ, 1 μM BA, and 1 μM IBA). After 12 weeks, the greatest number (1.8) and longest shoots (18.7 mm) were in cultures incubated on the shoot formation medium for 3 weeks. In a separate experiment, dissected seeds were placed on shoot formation medium. Seedcoats were removed after 10 days in vitro. Explants were transferred to shoot elongation medium after 4 weeks in vitro. There were more shoots (2.5) on 12-week-old explants without seedcoats than on explants with seedcoats (0.9). This result may be related to inhibitors in the testa.