Improving the germination of somatic embryos of Picea morrisonicola Hayata: effects of cold storage and partial drying

Abstract

Mature somatic embryos (SEs) of Taiwan spruce (Picea morrisonicola Hay.) were harvested from embryogenic tissues incubated on a filter paper laid on an abscisic acid (ABA)-containing medium. The effects of cold storage and partial drying on embryo germination and on reduction of embryo ABA content were determined. Percentage germination was low (<10 %) and hyperhydricity was high (>86.8 %) for mature SEs (control). Both cold storage and partial drying significantly reduced this physiological abnormality. Germination increased to 49.1 % for SEs that received cold-storage treatment, and their ABA content was reduced to a trace amount (2.4 ± 1.1 μg/g dw). Germination increased to 58.1 % for SEs partially dried for 7 days, and the ABA content was relatively high (62.8 ± 21.7 μg/g dw). Hyperhydricity-induced failure to germinate among SEs containing low levels of ABA is discussed. Histological study revealed vigorous differentiation in the root apical meristem of SE during partial drying. This advanced development also accounted for the enhanced germination performance compared with other treatments. A combination treatment (partial drying and cold storage) increased percentage germination even further (69.9 %) and more effectively reduced hyperhydricity (18.7 %) during SE germination.