INFLUENCE OF ABA ON STORAGE POSSIBILITIES IN VITRO OF LILACS

The collection of lilacs in the Plant Tissue Culture Laboratory of National Botanical Garden has 24 cultivars of Syringa vulgaris L. (including 5 ones originated in Latvia), one – S. vulgaris L. x S. oblata Lindl. and one – S. chinensis Willd. adopted for our climatic conditions. The aim of this present study was to find out a transition-term storage protocol for lilac leading to juvenilization and preconditioning for long storage. The effect of growth regulator abscisic acid (ABA) on morphological parameters and stress enzymes was tested. The role of ABA in concentrations 0; 0.3; 1; 4; 10 mg L^-1 or 0 + activated charcoal, 2 g L^-1 applied in the culture medium, was examined for optimisation of low growth of plantlets. The results demonstrate a positive influence of ABA in these concentrations both as in leaves and stems. Other variants had given a little better effect than control, 10 mg L^-1 ABA in stems except. The decreased activity of peroxidase and polyphenol oxidase in leaves under the effect of 10 mg L^-1 ABA could be interpreted with analogy of autumn conditions, what find expression in turning of biochemical processes to destruction of enzymatic system. We had concluded that the single initial dose of moderate concentration of ABA was sufficient for induction of dormancy-like conditions in lilac plantlets. Peroxidase activity in lilac stems was a good marker for plantlet physiological state after 6 months of cold storage. In contrast, polyphenol oxidase did not correlate with plantlet viability. The single dose of ABA in the culture medium in concentration from 0.3 to 1 mg L^-1 could be used in further experiments for long-term storage.