EFFECTS OF ABSCISIC-ACID ON THE INDUCTION OF DESICCATION TOLERANCE IN CARROT SOMATIC EMBRYOS

Effects of abscisic acid (ABA) on the induction of desiccation tolerance in carrot somatic embryos were investigated. The somatic embryos formed in hormone-free Murashige and Skoog's (MS) liquid medium were treated with ABA. After ABA treatment, the embryos were rapidly dehydrated with silica gels, and then the dried embryos were rehydrated on hormone-free solid MS medium. In this system, embryos treated with ABA showed regrowth after rehydration without any coating treatment and developed into plantlets. In contrast, almost all the embryos not treated with ABA did not survive after desiccation. The developmental stage of the embryos was critical for response to ABA, and 15-day-old torpedo-embryos (2.0 mm in length) showed the highest viability. The ABA treatment at concentrations higher than 10(-5) M induced high viability of the embryos after desiccation, whereas the embryos treated with 10(-3) M ABA formed secondary embryos but did not develop into plantlets. The viability of somatic embryos after desiccation increased gradually with longer duration of ABA treatment. The maximal viability of the somatic embryos was about 77 %, obtained by treatment with 10(-5) M ABA for 8 days.