Somatic embryogenesis (SE) in conifers has proven to be an useful biotechnological tool for
species conservation and mass propagation, but to make it commercially viable, adaptive
research is required to convert laboratory protocols into plantation reality. Hybrid white pines
are of interest to forest industry in North America due to the potential resistance to white pine
blister rust (Cronartium ribicola). Somatic embryos of many pine species are typically
germinated on the same nutrient medium as used for earlier stages of SE. For most of the
genotypes of white and hybrid white pine, the time required for the plantlets to grow a 2 cm
root takes approximately five to six months at which time the plantlets can be potted and
transferred to a greenhouse. The survival of plants is however sketchy and not always reliable.
In order to accelerate and improve the root growth and survival of the plants in a greenhouse a
study was initiated on the manipulation of the nitrogen composition of the germination
medium. We were interested in learning whether the pine somatic seedlings had a preference
for organic or inorganic forms of N during the germination step and root growth. Experiments
have been conducted to determine the uptake and content of 15N in those roots by submerging
them in a hydroponic solution for two hours. The somatic seedlings’ root growth was
dramatically affected by the N composition of the medium as well as it did affect the uptake of
15N. To follow up the nitrogen metabolism in somatic seedlings, we have performed
microarray and qPCR analysis for nitrogen or nitrogen-related metabolism genes. The results
of the analysis will be discussed.
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