The effect of low temperature and GA(3) treatments on dormancy breaking and activity of antioxidant enzymes in Fritillaria meleagris bulblets cultured in vitro

Abstract

We investigated the effect of low temperature and gibberellic acid (GA(3)) treatment on dormancy in Fritillaria meleagris L. bulbs. Also, we studied the effect of dormancy breaking on the antioxidant enzymes activity. To overcome dormancy, bulbs require a period (4-8 weeks) of exposure to low temperature. Bulbs regenerated in vitro were grown in the dark on medium without growth regulators at the standard (24 A degrees C) or at low temperatures (4 and 15 A degrees C) for 4, 6, 8 and 10 weeks. Bulbs were collected after 3, 4 and 5 weeks of cooling at 4 A degrees C. To investigate the influence of GA(3) on dormancy, bulbs were treated for 24 h with GA(3) solutions with 1, 2 and 3 mg l(-1) concentrations. During the period of growth of bulbs at 4 A degrees C, regeneration of bulbs was very weak, while at 15 A degrees C the number of regenerated bulbs increased significantly. Improved bulb sprouting was achieved by a short treatment with gibberellin. Low temperature also represents a kind of oxidative stress for the plant. The activity of superoxide dismutase, catalase (CAT) and peroxidase (POX) in bulbs of F. meleagris L. grown in vitro and ex vitro increased with decreasing temperature in contrast to glutathione reductase. POX showed generally lower activity than CAT which indicates that major role in the breaking dormancy and preparing bulbs for sprouting have catalases.