ناصر عسکری

Lilium (Liliaceae) is a considerable floricultural production and the third main bulbous plant in the floral market. Due to the advantages of lily bulbs such as compactness, robustness, easy transportation, more propagation, saving time and cost, and increased efficiency, its use is recommended. In lily, bulblet micropropagation is a successful method for solving acclimatization problems and also increasing plant growth in the sowing phase. The present study was conducted to investigate the effect of thermal stress on growth parameters (number of bulblets per explants, fresh weight of bulblet, scales, leaf, and root) in lily under in vitro circumstances. Three thermal stress [12 weeks 20 ºC (T1), 6 weeks 5 ºC+12 weeks 20 ºC (T2), and 6 weeks 20 ºC+6 weeks 5 ºC+6 weeks 20 ºC (T3)] were used in this experiment. The medium (MS) was composed of supplemented with 3% sucrose (w/v), 0.27 μM naphthalene acetic acid (NAA), and 0.7% (w/v) agar. The pH was adjusted at 5.8. Following to surface sterilization of lilyʼs scales, the explants were cultured and were placed at 24˚C of 8/16 h light photoperiod. The results illustrated that explants grown under cold pretreatment (T2) had the highest bulblet number (16.2) compared to the rest. Furthermore, in this treatment, the maximum fresh weight of bulblet (111.5 mg) and scales (152.7 mg) was found. Although the leaf's fresh weight (448.6 mg) was the highest in treatment T2, the fresh weight of the root (155 mg) was the lowest in this treatment. The uttermost root fresh weight was observed in T3 with 665 mg. Overall, Cold pretreatment at 5 ºC for 6 weeks and then putting explants at 20 ºC for 12 weeks improves the quantity and quality of lily bulbs.