BACKGROUND AND AIMS: Plant defence metabolites are considered costly due to diversion of energy and nutrients away from growth. These costs combined with changes in resource availability and herbivory throughout plant ontogeny are likely to promote changes in defence metabolites. A comprehensive understanding of plant defence strategy requires measurement of lifetime ontogenetic trajectories--a dynamic component largely overlooked in plant defence theories. This study aimed to compare ontogenetic trajectories of foliar phenolics and terpenoids. Phenolics are predicted to be inexpensive to biosynthesize, whereas expensive terpenoids also require specialized, non-photosynthetic secretory structures to avoid autotoxicity. Based on these predicted costs, it is hypothesized that phenolics would be maximally deployed early in ontogeny, whereas terpenoids would be maximally deployed later, once the costs of biosynthesis and foregone photosynthesis could be overcome by enhanced resource acquisition. METHODS: Leaves were harvested from a family of glasshouse-grown Eucalyptus froggattii seedlings, field-grown saplings and the maternal parent tree, and analysed for total terpenoids and phenolics. KEY RESULTS: Foliar phenolics were highest in young seedlings and lowest in the adult tree. Indeed the ratio of total phenolics to total terpenoids decreased in a significantly exponential manner with plant ontogeny. Most individual terpene constituents increased with plant ontogeny, but some mono- and sesquiterpenes remained relatively constant or even decreased in concentration as plants aged. CONCLUSIONS: Plant ontogeny can influence different foliar defence metabolites in directionally opposite ways, and the contrasting trajectories support our hypothesis that phenolics would be maximally deployed earlier than terpenoids. The results highlight the importance of examining ontogenetic trajectories of defence traits when developing and testing theories of plant defence, and illustrate an advantage of concurrently studying multiple defences.
BACKGROUND AND AIMS: Plant defence metabolites are considered costly due to diversion of energy and nutrients away from growth. These costs combined with changes in resource availability and herbivory throughout plant ontogeny are likely to promote changes in defence metabolites. A comprehensive understanding of plant defence strategy requires measurement of lifetime ontogenetic trajectories--a dynamic component largely overlooked in plant defence theories. This study aimed to compare ontogenetic trajectories of foliar phenolics and terpenoids. Phenolics are predicted to be inexpensive to biosynthesize, whereas expensive terpenoids also require specialized, non-photosynthetic secretory structures to avoid autotoxicity. Based on these predicted costs, it is hypothesized that phenolics would be maximally deployed early in ontogeny, whereas terpenoids would be maximally deployed later, once the costs of biosynthesis and foregone photosynthesis could be overcome by enhanced resource acquisition. METHODS: Leaves were harvested from a family of glasshouse-grown Eucalyptus froggattii seedlings, field-grown saplings and the maternal parent tree, and analysed for total terpenoids and phenolics. KEY RESULTS: Foliar phenolics were highest in young seedlings and lowest in the adult tree. Indeed the ratio of total phenolics to total terpenoids decreased in a significantly exponential manner with plant ontogeny. Most individual terpene constituents increased with plant ontogeny, but some mono- and sesquiterpenes remained relatively constant or even decreased in concentration as plants aged. CONCLUSIONS: Plant ontogeny can influence different foliar defence metabolites in directionally opposite ways, and the contrasting trajectories support our hypothesis that phenolics would be maximally deployed earlier than terpenoids. The results highlight the importance of examining ontogenetic trajectories of defence traits when developing and testing theories of plant defence, and illustrate an advantage of concurrently studying multiple defences.
Authors: Sotirios C Kampranis; Daphne Ioannidis; Alan Purvis; Walid Mahrez; Ederina Ninga; Nikolaos A Katerelos; Samir Anssour; Jim M Dunwell; Jörg Degenhardt; Antonios M Makris; Peter W Goodenough; Christopher B Johnson Journal: Plant Cell Date: 2007-06-08 Impact factor: 11.277
Authors: Zalihe Hakki; Benjamin Cao; Allison M Heskes; Jason Q D Goodger; Ian E Woodrow; Spencer J Williams Journal: Carbohydr Res Date: 2010-07-21 Impact factor: 2.104
Authors: Mick E Hanley; Roger W R Shannon; Damien G Lemoine; Bethan Sandey; Philip L Newland; Guy M Poppy Journal: Ann Bot Date: 2018-11-30 Impact factor: 4.357
Authors: Jakob B Butler; Jules S Freeman; Brad M Potts; René E Vaillancourt; Dario Grattapaglia; Orzenil B Silva-Junior; Blake A Simmons; Adam L Healey; Jeremy Schmutz; Kerrie W Barry; David J Lee; Robert J Henry; Graham J King; Abdul Baten; Mervyn Shepherd Journal: Heredity (Edinb) Date: 2018-03-10 Impact factor: 3.821