Plants are sessile organisms susceptible to the interaction between various types
of stress, which has resulted in an evolved defense system that increases the synthesis of secondary metabolites (Ghorbanpour et al. 2014). The variety of stress
factors together can affect the plant physiology, plant-plant interaction, defense
type, reproductivity, among others. For example, salinity and low/high-temperature
are conditions which restrict plant growth and productivity (Akula and Ravishankar
2011). In the signaling response to pathogens or herbivorous insects, several
response pathways are invoked, some of these are induced by infection and some
are performed regardless of the antimicrobial nature (Zaynab et al. 2018). Another
example is the interaction between plants and herbivory insects that causes the plant
to emit volatile organic compounds which influence the plant-to-plant communication, pollinators, and other insects, and increase fluidity of cell membranes for
thermo-tolerance and leaf tissue protection from atmospheric oxidants within and
around leaves (Faiola and Taipale 2020).
The foregoing indicates that plants can react in various ways in the presence of
one or more stress factors and that, in the same way, the response to the stimulus
may be the activation of a synthesis pathway of only one metabolite or a series of
secondary metabolites. For this reason, this work will focus on stress factors and the
production of secondary metabolites in plants.
5.2 Abiotic Stress
“Any unfavorable condition or substance that affects or blocks a plant's metabolism, growth or development” is the definition of plant stress suggested by
Lichtenthaler (1996). Currently, this definition has been modified depending on the
stimulus origin, defining as stress factors those stimuli that are external to the plant,
biotic (fungi, insects, etc.) or abiotic (temperature, luminosity, nanoparticles, metals
and polluting salts, water, etc.) (Kranner et al. 2002; Thakur et al. 2019). Abiotic
stress origin is not biological and can be divided into chemical or physical
(Vázquez-Hernández et al. 2019). For example, the adaptation to cold environments
in some plants is the result of an increase in the synthesis of flavonoids due to
acclimatization processes at low temperatures or by the application of UV radiation
(Samanta et al. 2011; Nakabayashi et al. 2014). In Vitis vinifera, it has been
observed that stimulation with heavy metals such as Cadmium (Cd
2+ ), Cobalt
(Co
2+ ) and Silver (Ag
+
), can increase the synthesis of Resveratrol (Cai et al. 2013),
while the application of UV-C irradiation induces the synthesis of stilbene (Wang
et al. 2010; Liu et al. 2010). This indicates that the synthesis of secondary
metabolites will depend on various factors such as the type of stimulus, the concentration, and the form of application. These same observations are appreciated by
Feregrino-Perez et al. (2018), where the effect of nanomaterials on germination,
development of plants, and synthesis of secondary metabolites is reviewed, concluding that the stress level will depend on the used nanomaterial, the dose and the
time of exposition. Low/high-temperature, relative humidity in air, drought,
5 Role of Stress and Defense in Plant Secondary Metabolites …
153
of stress, which has resulted in an evolved defense system that increases the synthesis of secondary metabolites (Ghorbanpour et al. 2014). The variety of stress
factors together can affect the plant physiology, plant-plant interaction, defense
type, reproductivity, among others. For example, salinity and low/high-temperature
are conditions which restrict plant growth and productivity (Akula and Ravishankar
2011). In the signaling response to pathogens or herbivorous insects, several
response pathways are invoked, some of these are induced by infection and some
are performed regardless of the antimicrobial nature (Zaynab et al. 2018). Another
example is the interaction between plants and herbivory insects that causes the plant
to emit volatile organic compounds which influence the plant-to-plant communication, pollinators, and other insects, and increase fluidity of cell membranes for
thermo-tolerance and leaf tissue protection from atmospheric oxidants within and
around leaves (Faiola and Taipale 2020).
The foregoing indicates that plants can react in various ways in the presence of
one or more stress factors and that, in the same way, the response to the stimulus
may be the activation of a synthesis pathway of only one metabolite or a series of
secondary metabolites. For this reason, this work will focus on stress factors and the
production of secondary metabolites in plants.
5.2 Abiotic Stress
“Any unfavorable condition or substance that affects or blocks a plant's metabolism, growth or development” is the definition of plant stress suggested by
Lichtenthaler (1996). Currently, this definition has been modified depending on the
stimulus origin, defining as stress factors those stimuli that are external to the plant,
biotic (fungi, insects, etc.) or abiotic (temperature, luminosity, nanoparticles, metals
and polluting salts, water, etc.) (Kranner et al. 2002; Thakur et al. 2019). Abiotic
stress origin is not biological and can be divided into chemical or physical
(Vázquez-Hernández et al. 2019). For example, the adaptation to cold environments
in some plants is the result of an increase in the synthesis of flavonoids due to
acclimatization processes at low temperatures or by the application of UV radiation
(Samanta et al. 2011; Nakabayashi et al. 2014). In Vitis vinifera, it has been
observed that stimulation with heavy metals such as Cadmium (Cd
2+ ), Cobalt
(Co
2+ ) and Silver (Ag
+
), can increase the synthesis of Resveratrol (Cai et al. 2013),
while the application of UV-C irradiation induces the synthesis of stilbene (Wang
et al. 2010; Liu et al. 2010). This indicates that the synthesis of secondary
metabolites will depend on various factors such as the type of stimulus, the concentration, and the form of application. These same observations are appreciated by
Feregrino-Perez et al. (2018), where the effect of nanomaterials on germination,
development of plants, and synthesis of secondary metabolites is reviewed, concluding that the stress level will depend on the used nanomaterial, the dose and the
time of exposition. Low/high-temperature, relative humidity in air, drought,
5 Role of Stress and Defense in Plant Secondary Metabolites …
153