Meta-topolin applied in proliferation increas the yield of Norway spruce somatic embryos

In four unrelated embryogenic lines of Norway spruce, the application of meta -topolin ( m T) instead of the commonly used 6-benzyladenine (BAP) during proliferation led to a positive effect on the subsequent maturation phase, when cytokinin is no longer applied. Although, both, BAP and m T are aromatic cytokinins, and differ only in the presence of a hydroxyl group in m T, the application of m T resulted in an increased yield of good-quality mature embryos. Furthermore, in selected line C (derived in our laboratory) we have examined the consequences of BAP vs. m T use that underlay the modified culture behaviour, persisting until late maturation. Our results showed modifications of hormonal balance in BAP, resp. m T variants including not only members of the cytokinin group (including metabolites), but also other phytohormones (abscisic acid, indole acetic acid, salicylic acid) and compounds with prominent protective and signalling roles (ascorbate, glutathione, sugars). This indicates the creation of a memory imprint of m T in the proliferation phase that is preserved and passed onto subsequent phases, directing further development. We assume that the m T could allow for better realization of the embryonic potential of a given line, that the BAP is unable to accomplish.