Phosphorus (P) is a component of molecules such as nucleic acids, lipids and
nucleotides with an energy function (ATP and ADP). Plants uptake P in the form of
inorganic orthophosphate (Pi, HPO 4
2− , and H 2 PO 4− ) which deficiency promotes
anthocyanin synthesis (Jezek et al. 2016). Peng et al. (2019) proposed a model of
com-modulation (miR399d) and epigenetic modification as a regulatory mechanism
of anthocyanin synthesis that depends on the P availability. Sulfur is a structural
component of amino acid precursors of secondary metabolites. Therefore, its
deficiency negatively affects the biosynthesis of lycopenes and carotenoids
(Mohammed et al. 2015). Micronutrient deficiencies are shown to have a negative
impact on the synthesis of phenolic compounds and terpenes. Micronutrients such
as Cu, Fe, Mo, and Mn, act as factors for the synthesis of secondary metabolites.
5.3 Biotic Stress
Biological stressors are those considered within living organisms (plants or
pathogens) including bacteria, insect or herbivores, fungi, phytohormones, and
miRNA, among others, that results in biotic stress (Patel and Krishnamurthy 2013).
The action mechanism of this factor includes activation or inactivation of enzymes,
interaction with receptors, ion channels, stimulation of bioactive compounds, and so
forth (Joshi et al. 2019). Some biotic stress factors and their role in the synthesis of
secondary metabolites in plants are described below.
5.3.1 Bacteria and Viruses
Plants are exposed to interactions with other living things. The interaction between
microorganisms and plants can have positive effects. Microorganism colonization
(pathogens and non-pathogens) triggers the resistance mechanism of the plant,
conferring resistance against other stressors (Nejat and Mantri 2017; Choudhary
et al. 2016). Nonpathogenic microorganisms act as plant biostimulants. A plant
biostimulant is defined as any substance or microorganism applied to plants in order
to improve nutritional efficiency, tolerance to biotic and abiotic stress, and quality
(Van Oosten et al. 2017; Du Jardin 2015). Arbuscular mycorrhizal fungi,
Trichoderma, and plant growth-promoting rhizobacteria are biostimulant microorganisms used in crops.
Microorganisms can confer a certain degree of tolerance against abiotic stress
conditions. Colonized plants produce a wide range of enzymes and metabolites that
allow them to generate tolerance to stress (Miliute et al. 2015). Some genera of
bacteria like Rhizobium, Bacillus, Pseudomonas, Pantoea, Paenibacillus,
Burkholderia, Achromobacter, Azospirillum, Microbacterium, Methylobacterium,
variovorax, Enterobacter, have been shown to induce tolerance to abiotic stress
(Choudhary et al. 2016; Naveed et al. 2014; Gururani et al. 2013). Tolerance
176
H. Aguirre-Becerra et al.
nucleotides with an energy function (ATP and ADP). Plants uptake P in the form of
inorganic orthophosphate (Pi, HPO 4
2− , and H 2 PO 4− ) which deficiency promotes
anthocyanin synthesis (Jezek et al. 2016). Peng et al. (2019) proposed a model of
com-modulation (miR399d) and epigenetic modification as a regulatory mechanism
of anthocyanin synthesis that depends on the P availability. Sulfur is a structural
component of amino acid precursors of secondary metabolites. Therefore, its
deficiency negatively affects the biosynthesis of lycopenes and carotenoids
(Mohammed et al. 2015). Micronutrient deficiencies are shown to have a negative
impact on the synthesis of phenolic compounds and terpenes. Micronutrients such
as Cu, Fe, Mo, and Mn, act as factors for the synthesis of secondary metabolites.
5.3 Biotic Stress
Biological stressors are those considered within living organisms (plants or
pathogens) including bacteria, insect or herbivores, fungi, phytohormones, and
miRNA, among others, that results in biotic stress (Patel and Krishnamurthy 2013).
The action mechanism of this factor includes activation or inactivation of enzymes,
interaction with receptors, ion channels, stimulation of bioactive compounds, and so
forth (Joshi et al. 2019). Some biotic stress factors and their role in the synthesis of
secondary metabolites in plants are described below.
5.3.1 Bacteria and Viruses
Plants are exposed to interactions with other living things. The interaction between
microorganisms and plants can have positive effects. Microorganism colonization
(pathogens and non-pathogens) triggers the resistance mechanism of the plant,
conferring resistance against other stressors (Nejat and Mantri 2017; Choudhary
et al. 2016). Nonpathogenic microorganisms act as plant biostimulants. A plant
biostimulant is defined as any substance or microorganism applied to plants in order
to improve nutritional efficiency, tolerance to biotic and abiotic stress, and quality
(Van Oosten et al. 2017; Du Jardin 2015). Arbuscular mycorrhizal fungi,
Trichoderma, and plant growth-promoting rhizobacteria are biostimulant microorganisms used in crops.
Microorganisms can confer a certain degree of tolerance against abiotic stress
conditions. Colonized plants produce a wide range of enzymes and metabolites that
allow them to generate tolerance to stress (Miliute et al. 2015). Some genera of
bacteria like Rhizobium, Bacillus, Pseudomonas, Pantoea, Paenibacillus,
Burkholderia, Achromobacter, Azospirillum, Microbacterium, Methylobacterium,
variovorax, Enterobacter, have been shown to induce tolerance to abiotic stress
(Choudhary et al. 2016; Naveed et al. 2014; Gururani et al. 2013). Tolerance
176
H. Aguirre-Becerra et al.