stress signals lead to the production of a great amount of secondary metabolites
due to the activation of different defense pathways (Ncube et al. 2012).
Application of pre-postharvest elicitors can trigger distinct changes in the
secondary metabolism of plants. The effect of elicitors in plant’s metabolism is
reviewed in the next section.
In summary, since plants are sessile organisms, they cannot escape from extreme
environmental conditions, thus they have evolved complex mechanisms in order to
adapt to the conditions to which they are exposed (Ramakrishna and Ravishankar
2011). Secondary metabolites are an integral component of the plant adaptive
mechanisms. The relation between environment and agronomic practices on plant
secondary metabolites may be direct or indirect, cultivar and crop specific, and
short-lived or sustained. However, further knowledge of plant metabolism is still
needed, because currently, although possible, it is a difficult issue to achieve both
yield and phytochemical production (Martínez-Ballesta et al. 2008) (Table 1.2).
1.11.3.1 Elicitors Application in a Space–Time Manner in Plants
The first idea for the use of elicitors in agriculture was related to the increasing of
plant resistance to pathogens (Boughton et al. 2006), however, it was found that
they also increase the plant secondary metabolites because they mimic various
stresses encountered by a plant. Consequently, they are seen as an alternative for
obtaining plants with improved health properties (Ruiz-García and Gómez-Plaza
2013) and as a way to develop sustainable agriculture production; taking into
account not only a minimized use of pesticides but also their use in crops could
improve consumer’s health (Capanoglu 2010).
Plant defense mechanisms are based on prevention, tolerance, or resistance
(Thakur 2007). These mechanisms are activated in different ways, depending on
the type of pathogens attacking the plant (or biotrophs appearing necrotrophic)
(Jalali et al. 2006). Such mechanisms may be constitutive or induced. The first
provides protection of initial invasion of a pathogenic agent by physical barriers or
preformed biochemical. Whereas induced resistance is only activated as a response
to pathogen attack (Cruz-Borruel et al. 2006). Activation of an effective defense by
plant is based on speed with which it can recognize the pathogen (Fornoni et al.
2004). This is achieved through the activation signals induced by nonspecific
elicitors and specific compounds that are first recognized by the plant to activate
signaling cascade and therefore defense response (Ebel and Cosio 1994).
Table 1.2 Influence of some environmental factors on the production of secondary metabolite
Stress factor
Plant species Secondary metabolite References
Salinity
Pepper
Lycopene
Phenols
Navarro et al. (2006)
Radiation
Pepper
Flavonoids
Sarghein et al. (2008)
Electrical conductivity
Tomatoes
Lycopene
Wu and Kubota (2008)
Heat shock, chilling, radiation Lettuce
Phenolic compounds Oh et al. (2009)
34
L. Garcia-Mier et al.
due to the activation of different defense pathways (Ncube et al. 2012).
Application of pre-postharvest elicitors can trigger distinct changes in the
secondary metabolism of plants. The effect of elicitors in plant’s metabolism is
reviewed in the next section.
In summary, since plants are sessile organisms, they cannot escape from extreme
environmental conditions, thus they have evolved complex mechanisms in order to
adapt to the conditions to which they are exposed (Ramakrishna and Ravishankar
2011). Secondary metabolites are an integral component of the plant adaptive
mechanisms. The relation between environment and agronomic practices on plant
secondary metabolites may be direct or indirect, cultivar and crop specific, and
short-lived or sustained. However, further knowledge of plant metabolism is still
needed, because currently, although possible, it is a difficult issue to achieve both
yield and phytochemical production (Martínez-Ballesta et al. 2008) (Table 1.2).
1.11.3.1 Elicitors Application in a Space–Time Manner in Plants
The first idea for the use of elicitors in agriculture was related to the increasing of
plant resistance to pathogens (Boughton et al. 2006), however, it was found that
they also increase the plant secondary metabolites because they mimic various
stresses encountered by a plant. Consequently, they are seen as an alternative for
obtaining plants with improved health properties (Ruiz-García and Gómez-Plaza
2013) and as a way to develop sustainable agriculture production; taking into
account not only a minimized use of pesticides but also their use in crops could
improve consumer’s health (Capanoglu 2010).
Plant defense mechanisms are based on prevention, tolerance, or resistance
(Thakur 2007). These mechanisms are activated in different ways, depending on
the type of pathogens attacking the plant (or biotrophs appearing necrotrophic)
(Jalali et al. 2006). Such mechanisms may be constitutive or induced. The first
provides protection of initial invasion of a pathogenic agent by physical barriers or
preformed biochemical. Whereas induced resistance is only activated as a response
to pathogen attack (Cruz-Borruel et al. 2006). Activation of an effective defense by
plant is based on speed with which it can recognize the pathogen (Fornoni et al.
2004). This is achieved through the activation signals induced by nonspecific
elicitors and specific compounds that are first recognized by the plant to activate
signaling cascade and therefore defense response (Ebel and Cosio 1994).
Table 1.2 Influence of some environmental factors on the production of secondary metabolite
Stress factor
Plant species Secondary metabolite References
Salinity
Pepper
Lycopene
Phenols
Navarro et al. (2006)
Radiation
Pepper
Flavonoids
Sarghein et al. (2008)
Electrical conductivity
Tomatoes
Lycopene
Wu and Kubota (2008)
Heat shock, chilling, radiation Lettuce
Phenolic compounds Oh et al. (2009)
34
L. Garcia-Mier et al.