MATERIALS AND METHODS
Explant preparation for callus induction: For callus induction, three types of explants including hypocotyl, cotyledon and leaf explants were chosen. Hypocotyl and cotyledon explants were excised from 12-14 day-old seedlings. The exact site of hypocotyl and cotyledon explants was shown in Fig. 1. The explants were cut into 3-4 mm in length for both cotyledon and hypocotyls. The leaf explants were taken from 30-35 day-old seedlings cultured in vitro while they had 4-5 true leaves. For excision of leaf explants into 5-6 mm in length, the main vein surrounded tissues shown in Fig. 2 were used as explant because this section has more meristematicsimilar cells than others sites.