Externí autoři: Václav Motyka

Somatic embryogenesis is a useful method for propagating selected plant material. However, before using this technique for forest tree deployment, it is important to ensure high-quality somatic embryos (SEs). This quality depends on how closely SEs resemble zygotic embryos (ZEs). At the end of their maturation, SEs usually resemble ZEs from fresh seeds due to their high water content and biochemical composition.

It is assumed that the production of somatic embryos (SEs), which closely resemble fully mature zygotic embryos (ZEs), increases the chance of producing somatic plants equivalent to seedlings. Desiccation is crucial to reduce the water content of SEs and to initiate biochemical changes that support germination and conversion into plants. We investigated the biological, histological, biochemical and molecular changes in the SEs of hybrid larch Larix eurolepis exposed to desiccation at high relative humidity (RH; 98 %), reduced RH (59 %), or a combination of both.

Somatic embryogenesis of conifers yields somatic embryos (SEs) that closely resemble non-mature cotyledonary zygotic embryos (ZEs). The most common method to improve the biochemical composition of SEs and reduce their water content to bring SEs closer to fully mature ZEs is cold treatment or desiccation at different relative humidity (RH). Both treatments can not only lead to successful SE germination but can also induce a stress response.

In Norway spruce, as in many other conifers, the germination capacity of somatic embryos is strongly influenced by the desiccation phase inserted after maturation. The intensity of drying during desiccation eminently affected the formation of emblings (i.e., seedlings developed from somatic embryos). Compared to non-desiccated embryos, the germination capacity of embryos desiccated at 100% relative humidity was about three times higher, but the reduction of relative humidity to 95% and 90% had a negative effect on the subsequent embryo development.

Exposure of Norway spruce (Picea abies) somatic embryos and those of many other conifers to post-maturation desiccation treatment significantly improves their germination. An integration analysis was conducted to understand the underlying processes induced during the desiccation phase at the molecular level. Carbohydrate, protein and phytohormone assays associated with histological and proteomic studies were performed for the evaluation of markers and actors in this phase.

Somatic embryogenesis techniques have been developed for most coniferous species, but only using very juvenile material. To extend the techniques’ scope, better integrated understanding of the key biological, physiological and molecular characteristics of embryogenic state is required. Therefore, embryonal masses (EMs) and non-embryogenic calli (NECs) have been compared during proliferation at multiple levels.

Conifer somatic embryogenesis (SE) is a process driven by exogenously supplied plant growth regulators (PGRs). Exogenous PGRs and endogenous phytohormones trigger particular ontogenetic events. Complex mechanisms involving a number of endogenous phytohormones control the differentiation of cells and tissues, as well as the establishment of structures and organs. Most of the mechanisms and hormonal functions in the SE of conifers have not yet been described.