Variation in constitutive and induced chemistry in the needles, bark and roots of young Pinus radiata trees

The capacity of trees to cope with pests and pathogens depends in part on the variation of constitutive and induced chemical defences within the plant. Here we examined the constitutive and induced variation of primary (sugars and fatty acids) and secondary (mono-, sesqui- and di- terpenoids as well as volatile phenolics) metabolites in the needles, bark and, for the first time, roots of 2-year old Pinus radiata. A total of 81 compounds were examined. The plant parts differed significantly in constitutive levels of individual sugars, fatty acids, mono-, sesqui- and di- terpenoids as well as volatile phenolics. Overall, the bark had more compounds and a higher amount of most secondary compounds and the levels of compounds in the roots differed from that of the needles and bark. For example, glucose was the dominant sugar in the needles and bark whereas fructose dominated in the roots. Of the fully identified secondary compounds, monoterpenoids dominated in all plant parts but with different qualitative patterns. Following methyl jasmonate and bark stripping treatments, a marked reduction in sugars but weaker changes in secondary compounds were detected in the needles and bark. Responses in the roots were minor but the few that were detected were mostly in response to the bark stripping treatment. Changes in correlations among chemicals within plant parts and between the same compound across the different plant parts were also detected after stress treatments. Overall, results showed that the constitutive composition in the roots differs from that of the bark and needles in P. radiata and inducibility is stronger in the primary than secondary metabolites and differs between plant parts. This detailed assessment of Pinus radiata chemistry in the needles, bark and roots, including the compounds that respond to simulated biotic stress will potentially facilitate the identification of related chemical defence traits.