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Genetic stability of physiological responses to defoliation in a eucalypt and altered chemical defence in regrowth foliage

Citation

Borzak, CL and Potts, BM and Barry, KM and Pinkard, EA and O'Reilly-Wapstra, JM, Genetic stability of physiological responses to defoliation in a eucalypt and altered chemical defence in regrowth foliage, Tree Physiology pp. 1-16. ISSN 0829-318X (2016) [Refereed Article]


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DOI: doi:10.1093/treephys/tpw101

Abstract

Defoliation may initiate physiological recovery and chemical defence mechanisms that allow a plant to improve fitness after damage. Such responses may result in changes in plant resource allocation that influence growth and foliar chemistry. In this study, we investigated the nature and stability of the defoliation response of juvenile plants from three divergent populations of Eucalyptus globulus Labill. A partial defoliation treatment that removed all upper crown leaves and the apical buds was applied to plants sourced from eight families from each of three populations representing contrasting chemical resistance to mammalian herbivory. Growth, photosynthetic rate and chlorophyll content were assessed pre-defoliation and periodically up to 12 weeks post-defoliation. The content of key plant primary and secondary metabolites was assessed pre-defoliation, at 12 weeks post-defoliation in the old foliage (positioned below the point of defoliation) and in the new foliage of the control plants and regrowth (from axillary buds) on the defoliated plants. There were clear treatment impacts on physiological responses, growth and foliar chemical traits, but despite significant constitutive differences in physiology, growth and chemistry the three E. globulus populations did not vary in their response to foliage loss. Distinct physiological responses to defoliation were observed with treatment plants showing significant up-regulation of photosynthetic rate and increased chlorophyll content in the old foliage remaining in the lower crown. There was a significant increase in the concentrations of a number of foliar chemical compounds in the regrowth arising from previously dormant axillary buds compared with new growth derived from apical meristems. There were changes in biomass allocation; defoliated plants had increased branching and leaf biomass, with changes in regrowth morphology to increase light capture. This study argues for multiple responses of E. globulus juveniles to defoliation involving apical bud loss, including elevated chemical defences matched with increased growth. From a chemical defence perspective, these responses create an enhanced chemical mosaic to the herbivore, with leaves remaining after partial browsing potentially being more palatable than the regrowth. This study demonstrates the multiple independent strategies plants may use to respond to partial defoliation and emphasizes the dynamic interplay between growth and defence in the recovery response.

Item Details

Item Type:Refereed Article
Keywords:chemical defence, defoliation, Eucalyptus, photosynthesis, quantitative genetics, seedling recovery, browsing, genetic variation, physiology
Research Division:Agricultural and Veterinary Sciences
Research Group:Forestry Sciences
Research Field:Forestry Pests, Health and Diseases
Objective Division:Plant Production and Plant Primary Products
Objective Group:Forestry
Objective Field:Hardwood Plantations
Author:Borzak, CL (Ms Christina Borzak)
Author:Potts, BM (Professor Brad Potts)
Author:Barry, KM (Dr Karen Barry)
Author:O'Reilly-Wapstra, JM (Dr Julianne O'Reilly-Wapstra)
ID Code:114431
Year Published:2016
Deposited By:TIA - Research Institute
Deposited On:2017-02-15
Last Modified:2017-02-28
Downloads:0

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