Callus and adventitious shoot formation in excised embryos of white pine (Pinus strobus)

Abstract

Excised embryos from 2- to 3-yr-old seeds of white pine (P. strobus) were grown on Murashige and Skoog medium supplemented with several concentrations of different plant hormones. In the basal medium the embryos developed into normal seedlings. At 1-2% sucrose concentration in the medium, the primary root of the embryo did not grow well, while at 3-6% sucrose concentration normal growth of the primary root was observed in most of the embryos. GA at a wide range of concentrations (0.01-20.0 mg/l) had little effect on the growth of the seedling shoot while growth of the primary root was generally suppressed. In the presence of 0.01-2 mg/l of NAA [naphthaleneacetic acid], 2,4-D or IBA, the embryos proliferated to form friable green callus. Callus formation was further enhanced by a cytokinin (0.1-5 mg/l). IBA (1-5 mg/l) in some embryos induced the formation of adventitious shoots from the hypocotyl region. Similarly, TIBA [triiodobenzoic acid] (0.5-1.0 mg/l) induced the formation of adventitious shoots but they were formed at the tips of embryonic cotyledons. The number of adventitious shoots per embryo was increased by zeatin or benzyladenine. The callus obtained on 2,4-D or IBA could be easily subcultured. In spite of several treatments with different auxins, cytokinins and their combination, no differentiation of roots or shoots was observed in callus cultures.