Antitranspirants putrescine and abscisic acid improve acclimatization of micropropagated spathiphyllum 'lima' regel

A crucial phase for successful plant micropropagation is the transfer from lab to greenhouse. This acclimatization coincides often with plant losses. The possibility to improve acclimatization of Spathiphyllum plantlets were evaluated by the application of antitranspirants putrescine and abscisic acid (ABA) 3 days before transfer to ex vitro conditions. Different concentrations of putrescine (0, 0.882, 2.645, 4.408 and 8.815 g.l-1) and ABA (0, 0.5, 5 and 50 mg.l-1) were screened. For putrescine only 2.645 g.l-1 resulted in higher acclimatization rates. Overall ABA improved acclimatization significantly compared to the control treatment. No significant difference in the relative water content (RWC) was observed between control and the antitranspirants treatments. The impact at the physiological level of the best treatments (putrescine 2.645 g.l-1 and ABA 0.5 mg.l-1) were studied more into depth. Transpiration rate and stomatal conductance revealed that the most stressful days are the first days of the acclimatization phase. Antitranspirants had little significant impact on photosynthetic parameters, nevertheless ABA-treated plantlets showed less stress according to chlorophyll a fluorescence parameters. The endogenous ABA content increased during the first day of the acclimatization process. This research shows that antitranspirants can enhance acclimatization but the causality of their effectiveness is not unambiguous.