Somatic embryogenesis in saffron:: Optimisation through temporary immersion and polyamine metabolism

Saffron embryogenic calli increased fresh weight four times when cultured in a temporary immersion system compared to those cultured in solid medium. Paclobutrazol was effective reducing hyperhydricity in the explants; the best results were obtained with 1 mg/l. The development of somatic embryos on solid medium was significantly improved with the addition jasmonic acid (0,5 mg/l). Saffron somatic embryos contained more conjugated than free polyamines. This was true for all stages of embryogenesis except for initial stage. The establishment of polar embryos determined a significant increase in the level of polyamines mainly due to a drastic rise in the conjugation of the diamines diaminepropane and putrescine. This stage was also characterized by the depletion of free diaminepropane. In dipolar embryos a decrease in the concentration of conjugated polyamines was observed. The last stage of regeneration, in which corms are well formed at the base of each plantlet, coincided with further reduction in total polyamines; the almost complete depletion of most free polyamines (only traces of putrescine and spermine are detected), being conjugated spermidine the most predominant amine.