The effect of arginine on root system development in Norway spruce (Picea abies L. Karst) somatic embryos
The demands for higher production yields and better quality materials from the forests are increasing globally. Tree breeding programs are directed to meet the future demands on forests. In order to capture the full benefits from the breeding programs, clonal propagation is necessary. For most conifer species, somatic embryogenesis (SE) is the only available option for large scale clonal propagation of Elite clonal material. For Norway spruce (Picea abies L. Karst.), SE procedures suitable for laboratory scale propagation have been available since the mid-1980s. The SE technique has a great potential for mass propagation of conifer species; however the implementation in forestry for plant production has so far been hampered by the labor intensive procedures making the technique costly. SE involves a series of developmental processes, starting with induction of embryogenic cultures from an initial explant, multiplication of somatic embryos in the proliferation phase, early embryo differentiation, maturation and germination.
The aim of this study was to investigate and characterize how organic nitrogen affects the first emergence and formation of the root system in maturated and germinated Norway spruce somatic embryos and plants. The present study suggests that organic nitrogen (arginine) interacts with glutamine and positively affects embryo germination and root development. It was also observed that the amino acid D-serine inhibits embryo germination at the concentrations tested here, and had no visible positive effect on root development during germination. Image analysis of the development of root systems, in planted SE plants, showed no significant difference between plants treated with 5 mg ammonium nitrate or arginine 5 mg. However, analyses of the amino acid content revealed that plants treated with 10 and 5 mg arginine had higher amino acids content than plants treated with 10 and 5 mg ammonium nitrate, respectively, which might indicate that arginine was preferable to ammonium nitrate as nitrogen source.