Indirect somatic embryogenesis and plant regeneration from leaf and internode explants of Paulownia elongata

Several plant growth regulators BA, TDZ, 2,4- and Kn were tested alone or in combination for their capacity to induce indirect somatic embryogenesis from leaf and internode explants of Paulownia elongata. Calli were produced when leaf explants were cultured on Murashige and Skoog (MS) medium containing 3 % sucrose, 0.4 % phytagel, 4 mg l-1 TDZ and 0.1 mg l-1 Kn after 3 weeks and the initiation rate was 54.1%. After subculturing on the same medium, embryos at various developmental stages (globular, heart and torpedo shaped) were transferred for maturation onto MS medium supplemented with 3 % sucrose, 0.4 % phytagel, 0.1 mg l-1 TDZ, 1 mg l-1 Kn and 2 mM glutamine. An average of 50.7 somatic embryos were obtained from 100 mg of embryogenic callus after 4 weeks at high frequency (64.7 %). Afterward, mature somatic embryos were isolated and cultured on hormone-free MS medium for germination (80 %) and development into plantlets. Plantlets were transferred to pots with a mixture of peat and perlite in a 3:1 ratio and showed a survival rate of 70–80 %. Plantlets regenerated by this procedure were morphologically identical to the donor material and developed normally in the greenhouse.