In vitro regeneration of Psoralea corylifolia Linn.: influence of polyamines during in vitro shoot development

A reliable and economically feasible in vitro plant regeneration protocol has been standardized for the Psoralea corylifolia Linn. using internodal segment explants. Optimized combination of 2 mg L-1 6-benzylaminopurine (BAP) with 0.2 mg L-1 alpha-napthaleneacetic acid (NAA) induced multiple shoots and also triggered endogenous accumulation of polyamine putrescine in the explants. Endogenous putrescine induced multiple shoots in the explants functioning synergistically with optimized 6-BAP-NAA combination. Rooting in the in vitro regenerated shoots was induced on half-strength MS medium supplemented with IBA (2 mg L-1). Regenerated plantlets were successfully acclimatized under greenhouse conditions with 95% survivability. In vitro shoot regeneration was achieved in the internodal segments cultured on MS medium supplemented with polyamines such as putrescine, spermine, and spermidine replacing conventional plant growth regulators (cytokinins or auxins). Putrescine (50 mu M) induced higher number of shoots than optimized cytokinin-auxin combination, promoted subsequent elongation of shoots, and induced spontaneous rooting in the regenerated shoots on the same medium. Exogenous putrescine (50 mu M) also triggered the accumulation of endogenous putrescine. Putrescine supplementation in the MS medium has been found to be more economical and reliable for in vitro plant regeneration that reduced the total time required for the complete plant regeneration.