The role of abscisic acid and plant growth regulators in tissue culture-induced rejuvenation of strawberry ex vitro

Plant growth regulators applied in vitro affected strawberry plant performance ex vitro for a period of up to 4 months. Benzyl-adenine and gibberellin enhanced juvenile characteristics; in general, more runners and monofoliolate leaves were produced, net photosynthesis was reduced, leaf diffusive resistance was increased and, on occasion, flowering was delayed. In contrast, abscisic acid and a gibberellin biosynthesis inhibitor, paclobutrazol, resulted in a more adult phenotype; specifically, flowering was earlier, net photosynthesis and leaf diffusive resistance rates were equal to those of adult plants, and fewer leaves were monofoliolate. Tissue culture-produced plants reacquire the adult phenotype earlier than seedlings mature. Abscisic acid application to seedlings also resulted in earlier and increased flowering.Endogenous abscisic acid concentrations were greater in adult plants and less in tissue culture and seedling plants at 3 and 7 weeks ex vitro, after germination or after adult runner propagation. No flowering occurred at 3 weeks in any propagation type and only runner-produced plants flowered at 7 weeks. At 15 weeks, no statistical difference in abscisic acid concentrations existed among propagation treatments and all propagation types flowered. The endogenous concentrations of abscisic acid in plants propagated by all three methods were much higher at three weeks compared to concentrations at 7 or 15 weeks.Abbreviations ABA +cis, trans-abscisic acid - BA benzyl-adenine - GC-SIM-MS combined gas chromatography-selected ion monitoring mass spectrometry - GA gibberellin A₃ - RS leaf diffusive resistance in sec cm^-1 - MS Murashige & Skoog medium devoid of plant growth regulators - Pn net photosynthesis in mol CO₂ fixed m^-2 sec^-1 - paclo paclobutrazol as 50WP - TC-plants plants produced from tissue culture - Tween20 polyoxyethylene-sorbitan monolaurate - RP runner plants - SDLG selfed seedlings