Effects of silver nitrate and polyethylene glycol on white spruce (Picea glauca) somatic embryo development: enhancing cotyledonary embryo formation and endogenous ABA content

Abstract

In vitro cultures and endogenous abscisic acid (ABA) analyses with gas chromatography‐selected ion monitoring‐mass spectrometry (GC‐SIM‐MS) were used to study the effects of AgNO3 and polyethylene glycol (PEG) on white spruce (Picea glauca) somatic embryo maturation and endogenous ABA contents, Normally, in the absence of ABA, white spruce somatic embryos cannot mature. However, AgNO3 and PEG stimulated somatic embryo maturation by increasing the number of cotyledonary embryos. A combination of 100 μM AgNO3 and 40 g l−1 PEG was the treatment that was most effective in enhancing cotyledonary embryo formation without exogenous ABA. Either AgNO3 or PEG was able to increase endogenous ABA levels of the embryogenic culture but a combination of AgNO3 and PEG was the most effective treatment. Stimulation of cotyledonary embryo formation by AgNO3 occurred only at low ABA levels, while PEG promoted embryo formation at all exogenous ABA concentrations. Germination tests indicated that AgNO3 had no negative effects on embryo germination and conversion while the PEG‐treated embryos failed to germinate.