Embryogenic culture lines T4 and T2 were initiated from two mature zygotic embryos of Picea morrisonicola Hay. Mature somatic embryos (SEs) were produced in culture line T2 but not in line T4 after 8-week abscisic acid (ABA) treatment. High performance liquid chromatography (HPLC) analysis of the endogenous indole-3-acetic acid (IAA) content has shown 7.5 times higher IAA production in T4 line than in T2 line during the proliferation phase. However, after ABA incubation the line T4 produced much less IAA than line T2. The application of an anti-auxin, 2,3,5-triiodobenzoic acid (TIBA) or 2-(4-chlorophenoxy)-2-methylpropionic acid (PCIB) induced culture line T4 to produce mature SEs. Both 1 lM TIBA and 5 lM PCIB increased the production of stage 2 SEs in T4 culture line when cultures were treated during the proliferation stage for 8 weeks. Occasionally cotyledonary (stage 3) SEs were even produced from treated T4 culture line. Both chemicals have also been demonstrated to significantly decrease the amount of IAA in the treated T4 and T2 embryogenic lines. However the decrease of the IAA level was not beneficial for SE production in the T2 embryogenic line. These results indicated the importance of endogenous IAA level in manipulating the process of SE maturation in spruce embryogenic cultures.

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