One solution of NaOCl (10%) was used in combination with four immersion times together with one no treatment (5, 10, 20, 30 and 40 min). Twenty shoot tips (1.0 cm long) excised from 25-year-old field grown trees were surface sterilized in 10% NaOCl and rinsed three times in sterile distilled water. Explants were cultured on the SIM.