Microshoot culture of Persian violet: Plant regeneration and in vitro flowering

The response of the microshoot explants (1 mm long) from Persian violet (Exacum affine Balf. f. ex Regel) to various in vitro manipulations was investigated. The best multiple shoot induction (about 100 shoots per explant) was observed after the microshoot explants were cultured on semi-solid Murashige and Skoog (MS) medium supplemented with 2.0 mg l−1 BAP for 6 weeks. Transfer of the new shoots (2 cm long) to MS medium containing 2.0 mg l−1 IBA for 6 weeks resulted in the best rooting response (18 roots per shoot). Subsequently, 82% of the rooted shoots (plantlets) were successfully hardened after ex-flasking and grown in soil. The shoots induced from microshoot explants were also found to form flowers under in vitro conditions on MS medium without addition of any plant growth regulator. Cutting off the shoot tip led to the development of more branches and in vitro flowers. A comparative study of the in vitro flowers and those formed in plants grown in soil (in vivo flowers) showed that the floral structures were mostly similar, except that the ovary and style of the in vitro flowers were slightly smaller than the in vivo ones. The viability of the pollen grains from in vitro flowers seemed to be higher than the pollen of in vivo flowers, but the highest pollen germination response (about 33%, in darkness at room temperature for 24 h) was exhibited by the pollen grains from both sources on an in vitro germination medium containing 5% sucrose was not different.