Improvement of nutrient medium for growth and embryogenesis of megagametophyte and embryo callus lines of <i>Picea abies</i>

Abstract

New macro and microelement solutions were formulated for stimulation of growth and embryogenesis in white and chlorophyllous megagametophyte and embryo callus lines of Picea abies (L.) Karst. Macroelement media with different NH 4 + and NO 3 − ratios (1:2 and 1:4), the increased level of several microelements and the effect of organic nitrogen (100 mg 1 −1 casein hydrolysate, 0.25 m M arginine and 0.5 m M glutamine) were tested with 4 combinations of growth regulators (2,4‐dichlorophe‐noxyacefic acid or indole‐3‐butyric acid, kinetin). Green chlorophyll‐containing, in contrast to white callus lines, grew quite well without exogeneously added organic nitrogen. The ratio between NH 4 + and NO 3 − was not significant. The increased levels (μ M ) of several microelements: B (200), Zn (50), I (25), Cu (1), Co (0.5) and in addition Ni (0.1) improved callus growth in some lines more than 50% (DW) compared to cultures grown on the micronutrients of Murashige and Skoog. The response of different callus lines varied with the combinations of growth regulators. Embryogenesis did not occur in chlorophyllous callus lines in any of the 24 media combinations tested, but some very good media could be found for white megagametophyte and embryo callus lines. Microelements, favourable combination of growth regulators and organic nitrogen were especially important. A megagametophyte callus subcultured for 4 years was also able to form numerous proembryos.