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Root growth of somatic plants of hybrid Pinus strobus (L.) and P. wallichiana (A. B. Jacks.) is affected by the nitrogen composition of the somatic embryo germination medium


Key message

This paper describes improvement in root growth of hybrid white pine somatic plants on a somatic embryo germination medium containing solely organic nitrogen sources.


Mature somatic embryos of F2 hybrid Pinus strobus × Pinus wallichiana backcrossed with P. strobus converted to plants but survival of the somatic plants was not satisfactory prompting the present study on somatic seedling root growth on germination media varying in nitrogen (N) composition. The media were modifications of Litvay’s (Litvay et al. in Plant Cell Rep 4:325–328, 1985) which included two main groups: G1, G2, G3, G4 all contained inorganic N with or without glutamine (Gln) or casein hydrolysate (CH) and G5, G6, G7 contained solely glutamine and/or CH. In addition, G8 was half-strength G1 (with organic N) and G9 was half-strength CD (Campbell and Durzan in Can J Bot 53:1652–1657, 1975) without organic N. The roots of plants growing on media containing solely organic N grew about 2.55 times longer than on those containing solely inorganic N or both inorganic and organic N. The longest roots grew on G7 supplemented with CH and on G5 with both CH and Gln. Microarray analysis of somatic plants germinated on G1 versus G7 revealed that depending on the N source the somatic plants displayed changes in the transcriptome resulting in the differential expression of a range of genes involved in essential processes for plant growth and development. Roots grown in the absence of inorganic N were capable of rapid uptake of labelled inorganic 15N during the 2 h incubation in the nutrient solution. The somatic plants from G5 medium acclimatized at the rate twice as high as those from G1 (with both inorganic and organic N) and G2 (solely inorganic N) under standard fertilization regime.

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Fig. 1
Fig. 2



Somatic embryogenesis




Modified Litvay’s medium


and Durzan medium


Casein hydrolysate




White pine blister rust


Uridine diphosphate


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This work was supported by Grants from the Spanish Ministerio de Economía y Competitividad (BIO2015-69285-R) and Junta de Andalucía (BIO-474) to M.T.L.L. We gratefully acknowledge the assistance of Dr. Javier Canales (University of Malaga) with microarray analysis, Mrs. Cathy Overton with the production of mature somatic embryos and acclimatization of somatic plants and Mrs. Michèle Bernier-Cardou for the statistical analyses (Natural Resources Canada, Canadian Forest Service).

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Correspondence to K. Klimaszewska.

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Communicated by K. Noguchi.

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Fig. S1 Comparison between microarray and qPCR expression data to validate the microarray hybridizations. Closed bars correspond to Log2FC from microarray data and open bars to Log2FC from qPCR ones. Selected genes from P. pinaster (SustainPineDB) were: PpChS (chalcone synthase), PpEAP (embryo-abundant protein), Pp40sRP (40s ribosomal protein s19), Pp24kdP (24 kDa seed maturation protein), PpNADH (nadh:ubiquinone oxidoreductase family protein), PpPSII (photosystem ii 10 kDa chloroplast), PpChl (chlorophyll a b-binding protein), PpEF1β (elongation factor 1-beta), PpGS1a (glutamine synthetase 1a) and PpGS1b (glutamine synthetase 1b) (PPTX 48 KB)

Supplementary material 2 (DOCX 39 KB)

Table S6 Results of microarray analysis (XLSX 1518 KB)

Table S7 List of primer sequences used for microarray validation (XLSX 1518 KB)

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Llebrés, M.T., Avila, C., Cánovas, F.M. et al. Root growth of somatic plants of hybrid Pinus strobus (L.) and P. wallichiana (A. B. Jacks.) is affected by the nitrogen composition of the somatic embryo germination medium. Trees 32, 371–381 (2018).

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  • Eastern white pine
  • Himalayan pine
  • 15N uptake
  • Root length
  • Somatic embryogenesis
  • Microarrays