Abstract
Hormonal control of flower induction and inflorescence development in vitro was investigated in Spathiphyllum. The effects of gibberellic acid (GA(3)) and sucrose on inflorescence development were studied in plantlets regenerated in tissue culture. GA(3) was mandatory for the shift from the vegetative to the reproductive stage. The effect of sucrose concentration on inflorescence bud development was studied in plantlets cultured in MS medium supplemented with 10 mg l(-1) GA(3). Sucrose concentration at 3 or 6% induced inflorescence development in, respectively, 83-85% of the plantlets. The effect of GA(3) and sucrose on inflorescence differentiation and development were also recorded in liquid culture using air-lift bioreactor. The best response was found in the same medium which was standardized as an optimum for solid culture, but the results were better than solid culture. In order to study the relationship between glutathione (GSH) and flowering, we also measured the oxidized and reduced GSH content in leaves throughout the culture period on 2 weeks interval. The GSH accumulation was more after 4 weeks until 6 weeks in GA(3) treated plantlets. Similarly, glutathione reductase which is involved in the recycling of reduced GSH providing a constant intracellular level of GSH, was also higher in GA(3) treated plantlets. The transient increase in GSH contents also correlated with the changes in measured gamma-glutamylcysteine synthetase (gamma-ECS) activity over the same period. The antioxidant enzyme activity in GA(3) treated plantlets also suggests that the plants suffered increased oxidative stress during the period of GA(3) treatment which subsequently increases GSH synthesis through activation of gamma-ECS and this promotes flowering by increasing endogenous GSH.