While the mechanisms under pinning this persistent responsiveness have yet to be resolved, transcript me analysis has suggested that a moderate response to the stress associated with the SE induction treatment could play an important role. Indeed, it has been well established that stress response is a key element for SE induction in a wide variety of plant species, although the underlying molecular pathways remain largely unknown. Developing more effective SE induction protocols is further exacerbated by a general lack of understanding of even the most fundamental molecular mechanisms associated with the formation and proliferation of tissues in culture, although advances in genomic technologies are beginning to generate important clues. The aim of this study was to investigate how shoot explants of adult radiata pines would respond to SE induction on media with varying quantities of 2,4-dichlorophenoxyacetic acid, naphthaleneacetic acid or picloram. Comparing tissues induced from primordial shoots with those induced from axillary shoots was another major aspect. In order to provide additional insights into the developmental character of the induced tissues, gene expression profiling was conducted using real-time qPCR. Specifically, transcriptional factors whose expression is reflective of tissue identity were targeted, along with genes linked to cellular metabolism, mitoticand meristematic Pramoxine hydrochloride activity. In order to provide a foundation upon which to compare the primordial and axillary shoot-derived tissues, three EM lines induced from immature zygotic embryos were also analyzed. The T0070907 primary objective of this study was to determine whether SE induction could be achieved within shoot explants collected from adult radiata pine trees, based on three central parameters: genotype, explant type, and auxin composition. This also included shoot explants taken from two somatic embryo-derived trees, based on the premise that they could have greater propensity to undergo SE induction than shoot explants of seed-derived trees.For example, young needles collected from 1-year-old somatic embryo-derived Norway spruce trees displayed a higher SE induction response as compared with explants taken from seed-derived trees of similar age.