ناصر عسکری

During in vitro culture, lily plantlets were treated with various mild stresses. The effects on (1) bulb growth and (2) resistance to severe stress were monitored. Short periods of abiotic stresses (a few hours) increased the growth of lily bulblets in vitro during a 6w period of growth following the stress. After a brief (1 h) hot air treatment (HAT) applied to 12 week-old plantlets, e.g., the bulblets responded with increased growth. The most effective temperature for HAT was 44 ± 0.4°C which increased bulblet growth by 30%. The most effective durations of HAT and hot water treatment (HWT) were 2 h and 3 h, respectively. In Stargazer, 6 h drought stress increased the growth of bulblets by maximally 40%. In Santander, though, drought stress decreased the growth of lily bulblets by 30%. Anaerobiosis (8h treatment) led to an increase of the growth of lily bulblets by 65% and 32% in Santander and Stargazer, respectively. Apart from this advantageous effect on the long run (weeks), a moderate HAT pre-treatment (1 h or 2 h 38 ± 0.4°C) protected lily bulblets against a severe, lethal HAT (2 h 51 ± 0.5°C) applied shortly (a few hours) later. In non-pretreated bulblets, the percentage survival was 13% and 27% in ῾Stargazer᾽ and ῾Santander᾽, respectively, and after the 2 h pretreatment 70% and 100%, respectively