Plants produce an immense array of metabolites oering a remarkable metabolic plasticity enablingplants to endure a life full of challenges and facilitate survival and reproductive tness.Plant metabolites are divided into general and specialized metabolites (bioactive natural productsor phytochemicals). General metabolites are common to all plants and are essential togrowth and reproduction. Specialized metabolites typically occur in specic plant lineages andare essential for how plants respond to their environment. Lately, it is becoming more evidentthat these two classes of metabolites are closely intertwined functionally.In the work presented in this thesis, I have used a number of highly diverse plant species tostudy the role and plasticity of plant metabolism using ferns (Phlebodium aureum and Pteridiumaquilium), a grass (Sorghum bicolor ) and owering trees (Eucalyptus and Corymbia sp.). Asa model compound class, I have investigated cyanogenic glucosides in many aspects from thebiosynthetic amino acid precursor, to the nal product stored in the plant. Cytochrome P450monooxygenases (CYPs) play a key role in mediating the metabolic complexity seen in plants,including the biosynthesis of cyanogenic glucosides. In particular, CYPs from the CYP79 familywith their unique ability produce oximes, compounds placed at metabolic bifurcation pointsbetween general and specialized metabolism.This thesis has revealed new knowledge regarding the multiplicity of roles oximes have in plants.For example, this thesis demonstrates that the oxime-metabolizing step and specic oxime geometricisoform (E- or Z-oxime) determines the downstream product. In S. bicolor, the CYP79A1specically catalyzes the conversion of L-tyrosine to (E)-p-hydroxyphenylacetaldoxime, the rststep in cyanogenic glucoside biosynthesis. CYP79s are present in gymnosperms and angiospermsbut are noticeably absent in monilophytes (ferns). In the cyanogenic fern, Pteridium aquilium,the biosynthesis of cyanogenic glucosides has thus been a mystery. Here it is demonstrated thata avin monooxygenase (FMO) called FOS1 catalyzes the conversion of the amino acid phenylalanineto its corresponding oxime and show that oxime formation has convergently evolved inseed and non-seed plants.The long-lived non-model plant, Eucalyptus, contains a plethora of specialized volatile andnon-volatile metabolites, including cyanogenic glucosides. The production of the cyanogenicglucoside prunasin is especially high in E. cladocalyx apical tips. The biosynthetic pathwayof cyanogenic glucosides in eucalypts had remained unresolved. This thesis presents the rstcharacterization of prunasin biosynthesis in Eucalyptus. It is demonstrated that the conversionof the oxime to its corresponding cyanohydrin in eucalypts requires an additional enzymatic stepcatalyzed by a CYP706 in addition to the single multifunctional CYP enzyme known from otherplant species. As in other higher plants, the initial step in prunasin syntesis in E. cladocalyx iscatalyzed by a CYP79. Intriguingly, acyanogenic Eucalyptus species possess an unprecedentedlarge number of CYP79s in their genomes. This nding lead to the hypothesis that EucalyptusCYP79s may function to produce volatile oximes from leaves and owers. An exhaustive studyof the leaf and ower branch volatiles emitted by eucalypt trees in the eld was conductedusing nine dierent Eucalyptus and Corymbia species. A complex volatile prole was observedemitted in all species investigated, including isoprene, mono- and sesquiterpenoids, benzenoidsand other volatile organic compounds, however no oximes were detected. Factors such as tissuetype, environmental conditions and diurnal regulation had a qualitative and quantitative eecton the emission proles.This thesis highlights some of the complex mechanisms behind plant plasticity and illustratethe intricate network regulating plant metabolism from gene to nal product. The dynamicmetabolic solutions invented by plants to adapt to a sessile life are truly fascinating.