Background and Aims: The development of plant secondary metabolites during early life stages can have significant ecological and evolutionary implications for plant–herbivore interactions. Foliar terpenes influence a broad range of ecological interactions, including plant defence, and their expression may be influenced by ontogenetic and genetic factors. This study investigates the role of these factors in the expression of foliar terpene compounds in Eucalyptus globulus seedlings.

Methods: Seedlings were sourced from ten families each from three genetically distinct populations, representing relatively high and low chemical resistance to mammalian herbivory. Cotyledon-stage seedlings and consecutive leaf pairs of true leaves were harvested separately across an 8-month period, and analysed for eight monoterpene compounds and six sesquiterpene compounds.

Key Results: Foliar terpenes showed a series of dynamic changes with ontogenetic trajectories differing between populations and families, as well as between and within the two major terpene classes. Sesquiterpenes changed rapidly through ontogeny and expressed opposing trajectories between compounds, but showed consistency in pattern between populations. Conversely, changed expression in monoterpene trajectories was population- and compound-specific.

Conclusions: The results suggest that adaptive opportunities exist for changing levels of terpene content through ontogeny, and evolution may exploit the ontogenetic patterns of change in these compounds to create a diverse ontogenetic chemical mosaic with which to defend the plant. It is hypothesized that the observed genetically based patterns in terpene ontogenetic trajectories reflect multiple changes in the regulation of genes throughout different terpene biosynthetic pathways.

Item Type:	Refereed Article
Keywords:	chemical defence, Eucalyptus globulus, seedlings, foliar terpenes, genetic variation, herbivory, monoterpene, ontogenetic trajectory, plant ontogeny, population divergence, secondary metabolite, sesquiterpene
Research Division:	Biological Sciences
Research Group:	Ecology
Research Field:	Terrestrial ecology
Objective Division:	Plant Production and Plant Primary Products
Objective Group:	Forestry
Objective Field:	Hardwood plantations
UTAS Author:	Borzak, CL (Ms Christina Borzak)
UTAS Author:	Potts, BM (Professor Brad Potts)
UTAS Author:	Davies, NW (Associate Professor Noel Davies)
UTAS Author:	O'Reilly-Wapstra, JM (Professor Julianne O'Reilly-Wapstra)
ID Code:	97658
Year Published:	2015 (online first 2014)
Funding Support:	Australian Research Council (DP120102889)
Web of Science® Times Cited:	14
Deposited By:	Plant Science
Deposited On:	2015-01-07
Last Modified:	2017-11-03
Downloads:	0