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SUMMARY
An efficient plant regeneration protocol has been developed from root explants of Psoralea corylifolia L., an endangered medicinally important herbaceous plant species belonging to the family Fabaceae. Nodular embryogenic callus was initiated from young root segments cultured on Murashige and Skoog (MS) medium (1962) supplemented with ctnaphthaleneacetic acid (NAA; 2.68-13.42 (mu)M) or 2,4-dichlorophenoxyacetic acid (2,4-D; 2.25-11.25 (mu)M) in combination with 6-benzylaminopurine (BA; 2.2 (mu)M), thiamine HCI (2.9 (mu)M), L-glutamine (342.23 (mu)M) and sucrose (3.0%, w/v). The highest frequency (95.2%) of embryogenic calluses was obtained on MS medium supplemented with the growth regulators NAA (10.74 (mu)M) and BA (2.2 (mu)M). Development and maturation of somatic embryos was achieved after transfer of embryogenic calluses to MS medium supplemented with 1.34 (mu)M NAA or 1.12 (mu)M 2,4-D and 4.4-13.2 (mu)M BA. The maximum number (13.8 +/- 1.34) of cotyledonary-stage somatic embryos was obtained on MS medium containing 1.34 (mu)M NAA and 13.2 (mu)M BA. Germination of somatic embryos occurred on MS medium without any growth regulators and also on MS medium enriched with BA (1.1-8.8 pU), although the maximum germination frequency (76.1%) was obtained on 4.4 (mu)M BA plus 1.45 FYI gibberellic acid (GA^sub 3^). Plant regeneration without complete somatic embryo maturation was also achieved by transferring clumps of nodular embryogenic calluses onto MSO medium or MS medium supplemented with NAA (1.34 (mu)M) and BA (2.2-8.8 (mu)M). The highest frequency of plant regeneration (93.3%) and mean number of plantlets (15.4 +/- 0.88) were obtained on MS medium containing 1.34 (mu)L=M NAA and 4.4 (mu)M BA. Regenerated plants with welldeveloped root systems were transferred to pots where they grew vigorously, attained maturity and produced fertile seeds.
Key words: Psoralea corylifolia; medicinal plant; root segment; somatic embryogenesis; plant regeneration.
INTRODUCTION
Rapid industrialization and urbanization has led to overexploitation and loss of valuable natural resources, including medicinally important herbaceous plants. Medicinal plants are an important source of compounds for the pharmaceutical industry. There are many species of medicinal plants which are rare, endangered, or threatened with extinction, and their germplasm needs to be conserved, multiplied and improved. Psoralea corylifolia L. is a rare and endangered herbaceous medicinal plant, widely distributed in the tropical and subtropical regions of the world (Jain, 1994). It is used in the...