In Vitro Protocol Development for Alexandrian Laurel

Alexandrian laurel (Danae racemosa L.) is a commercially popular broadleaf, dark evergreen shrub with arching branches that range up to three feet in height and four feet wide. Normal propagation is by seeds and division. When grown from seeds, however, germination often takes up to one and a half years and successful germination is only about 20%. Moreover, because of its slow-growth rate, it typically takes up to six years to produce a saleable one-gallon size plant. Because of the time it takes to reach maturity, a growth protocol that could greatly expedite the plant development is highly desirable. This study focused on developing protocols for efficient germination, seedling quality enhancement, and multiple seedling production. We were able to develop an efficient in vitro germination protocol using a GA₃ treatment that took only 2 to 3 months for seeds to germinate and achieved a germination rate 80 to100%. The vigor and growth of micro-propagated plantlets also were characterized by healthier looking and more abundant roots than conventionally seed propagated plants. We also tested the cytokinins BA and TDZ as a means of increasing in vitro shoot multiplication and seedling quality enhancement. We found that BA balanced seedling development by simultaneously accelerating shoot growth and slowing down root growth, whereas TDZ significantly promoted shoot multiplication and proliferation by producing 5-20 shoots per seed.