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Chapter Eleven - Plant secondary metabolites and the interactions between plants and other organisms
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- By Sue E. Hartley, Department of Biology, University of York, René Eschen, CABI, Julia M. Horwood, School of Life Sciences, University of Sussex, Lynne Robinson, School of Life Sciences, University of Sussex, Elizabeth M. Hill, School of Life Sciences, University of Sussex
- Edited by Glenn R. Iason, Marcel Dicke, Wageningen Universiteit, The Netherlands, Susan E. Hartley, University of York
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- Book:
- The Ecology of Plant Secondary Metabolites
- Published online:
- 05 August 2012
- Print publication:
- 19 April 2012, pp 204-225
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Summary
Introduction
The central role of plant secondary metabolites (PSMs) in mediating the ecological interactions between plants and other organisms is both well known and well studied, particularly in the case of the defensive responses of plants against attack by herbivores or pathogens (Dangl & Jones, 2001; Kessler & Baldwin, 2002). Furthermore, because plants face many simultaneous threats (Maleck & Dietrich, 1999; Paul et al., 2000), the chemical changes within plants in response to one attacking organism can influence the behaviour and performance of many others (Thaler et al., 2002; Biere et al., 2004). Thus, chemically mediated plant-based interactions have significant consequences for individual species, ecological communities and ecosystem function, so gaining an in-depth understanding of the chemical basis of these interactions is vital for ecologists (van der Putten, 2003; Dicke, 2006; Schuman & Baldwin, Chapter 15; Dicke et al., Chapter 16).
Recent advances in ecological genomics have demonstrated the complexity of plant responses to biotic challenges at the molecular level: hundreds of genes are now known to be up- or down-regulated in response to herbivore or pathogen attack (Zheng & Dicke, 2008). This has been of great benefit in understanding the molecular basis of plant defence, but microarray data alone cannot unravel the complexity and variability in plant responses, many of which are specific to particular types of natural enemy, and/or vary according to environmental conditions (Kant & Baldwin, 2007). Genomic analysis needs to be supported by manipulative experiments which assess all the metabolic responses of plants to environmental challenges as well as the molecular ones – so-called metabolomic approaches. Metabolomics is the systematic analysis of the set of metabolites synthesised by an organism at a particular ‘snapshot’ in time and can be described as providing the link between genotypes and phenotypes (Fiehn, 2002; Macel et al., 2010). Assuming that this set of metabolites reflects the interactions the plant is having with its abiotic and biotic environment, chemical ecologists can use this technique to study the mechanisms underpinning these interactions (Bundy et al., 2009), including those between plants and other organisms such as herbivores and pathogens (Allwood et al., 2008).
Chapter Nine - The soil microbial community and plant foliar defences against insects
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- By Alan C. Gange, School of Biological Sciences, Royal Holloway, University of London, René Eschen, CABI, Viviane Schroeder, School of Biological Sciences, Royal Holloway, University of London
- Edited by Glenn R. Iason, Marcel Dicke, Wageningen Universiteit, The Netherlands, Susan E. Hartley, University of York
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- Book:
- The Ecology of Plant Secondary Metabolites
- Published online:
- 05 August 2012
- Print publication:
- 19 April 2012, pp 170-189
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- Chapter
- Export citation
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Summary
Soil microbial communities
No plant in nature grows in a soil devoid of microorganisms. Plant roots are surrounded by a rich microbial community, which reaches greatest levels of abundance and diversity in the zone immediately surrounding the root, a micro-habitat known as the rhizosphere. It has been claimed that the rhizosphere is where most biodiversity on Earth exists (Hinsinger et al., 2009) and it is certainly one of the most dynamic and important ecosystems, through effects on plant growth and thus crop production and the structure and function of natural communities (Barrios, 2007).
The microbial community associated with plant roots contains a diverse array of bacteria, protozoa and fungi, some of which can be antagonistic to plant growth (pathogens), while others may appear to be benign or to have a range of beneficial effects. These latter effects include improved nutrient uptake by roots, chiefly through fixation and cycling of nitrogen, and mineralisation and uptake of phosphorus. Furthermore, soil microbes may increase plant growth by the synthesis of phytohormones (Costacurta & Vanderleyden, 1995), antagonism of deleterious soil bacteria and fungi by antibiotic production or depriving them of iron (Kloepper et al., 1980), alleviation of salt and drought stress (Evelin et al., 2009), enhancement of photosynthesis, and increasing resistance to foliar pathogens and insect predators (van der Ent et al., 2009). The fact that root-associated microorganisms can alter the resistance of foliar tissues to insect herbivores is a relatively recent discovery, and the aim of this review is to document these interactions and to explore their mechanisms.
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