Application. Terpenoid compounds of conifers offer some advantages over other molecular markers and should be considered for use in fingerprinting genetic materials, measuring genetic diversity, selecting for resistance to pests, and determining systematic relationships and adaptation of species and races.Abstract. Terpenoid substances in forest trees are versatile biochemical systems for use as genetic markers and for studying genetic regulation at the biochemical level. Univariate, multivariate and correlative data analyses from numerous studies on different coniferous species are presented. These data indicate that fitness values for most terpenes examined are probably so low as to be unmeasurable except in long evolutionary time spans. Variation patterns for monoterpenes often closely parallel racial differentiation for morphological traits and reflect the migratory history of species and species-complexes. Random drift and gene flow are likely the major influences on genetic organization of terpene variability. Mutation in regulatory genes may be responsible for quantitative variation within major gene systems for terpenes. The mono-, sesqui-and diterpene systems in conifers offer good opportunities for research on the nature of gene regulation in plants and its evolutionary significance.

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Of ten terpenes that comprise most of the volatiles of grand fir foliage only four were affected by addition of nitrogen. Levels of beta-phellandrene, camphene and bornyl acetate and terpinolene were significantly reduced with nitrogen added to the equivalent amount of 44.8 g/m. A quantity of 22.4 g/m did not affect terpene production. Several populations were examined and these did not respond consistently on a regional basis, yet a significant interaction effect was apparent between treatment and local population response. Overall, total yield of terpenes as a function of fertilization was not altered.