Root and shoot growth of Pinus strobus x P. wallichiana somatic plants is influenced by the nitrogen composition of the germination medium

摘要

Somatic embryogenesis (SE) in conifers has proven to be an useful biotechnological tool forspecies conservation and mass propagation, but to make it commercially viable, adaptiveresearch is required to convert laboratory protocols into plantation reality. Hybrid white pinesare of interest to forest industry in North America due to the potential resistance to white pineblister rust (Cronartium ribicola). Somatic embryos of many pine species are typicallygerminated on the same nutrient medium as used for earlier stages of SE. For most of thegenotypes of white and hybrid white pine, the time required for the plantlets to grow a 2 cmroot takes approximately five to six months at which time the plantlets can be potted andtransferred 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 astudy was initiated on the manipulation of the nitrogen composition of the germinationmedium. We were interested in learning whether the pine somatic seedlings had a preferencefor organic or inorganic forms of N during the germination step and root growth. Experimentshave been conducted to determine the uptake and content of 15N in those roots by submergingthem in a hydroponic solution for two hours. The somatic seedlings’ root growth wasdramatically affected by the N composition of the medium as well as it did affect the uptake of15N. To follow up the nitrogen metabolism in somatic seedlings, we have performedmicroarray and qPCR analysis for nitrogen or nitrogen-related metabolism genes. The resultsof the analysis will be discussed.