2.4
Silicon and Abiotic Stresses
As per the literature, the important roles attributed to Si in plants include elevation in
growth, crop yield, and quality, photosynthesis, nitrogen (N 2 ) fixation as well as
protection against abiotic and biotic stresses (Balakhnina and Borkowska 2013;
Steiner et al. 2018; Malhotra and Kapoor 2019; Zargar et al. 2019; Ahanger et al.
2020; Singh et al. 2020). Interestingly, the abiotic stresses are the first and foremost
reason that besets the annual productivity rate. Abiotic stresses include salinity,
extreme temperature, UV-B radiation, heavy metal/metalloid toxicity, mechanical
injury, nutrient deficit, nutrient toxicity, and drought (Sharma et al. 2020). All these
stresses result in oxidative, osmotic as well as an ionic inconvenience in plants that
ultimately culminate into reactive oxygen species (ROS) accumulation, altered
metabolic and physiological processes (Sharma et al. 2020). This ultimately results
in hampered growth and net productivity which affect the farmer fields, farmer
pockets, and overall economy (Sharma et al. 2020).
A plethora of lab-scale, greenhouse-level, and field experiments have been
conducted that endorses the numerous benefits of silicon on the plants growing
under adverse conditions (Soundararajan et al. 2014; Manivannan et al. 2016;
Luyckx et al. 2017; Liu et al. 2019; Malhotra and Kapoor 2019; Zargar et al.
2019; Ahanger et al. 2020). It has also been deduced that it is not single but an
amalgamation of key mechanisms that alleviate stresses which include: (1) attunement of antioxidant systems and osmolytes for harmful ROS detoxification,
(2) immobilization or complex formation/co-precipitation or compartmentation of
noxious metal ions and enhanced uptake of nutrients, (3) modifying water as well as
nutrients uptake processes, (4) regulating expression of various genes, phytohormone biosynthesis, maintenance of osmotic potential, photosynthetic apparatus, and
gaseous exchange, and (5) formation of Si–cuticle double layer (Tripathi et al. 2016;
Etesami and Jeong 2018; Etesami and Jeong 2020; Souri et al. 2020) (Fig. 2.2).
2.4.1 Drought
Drought imposes a grave threat to plant population on earth as the morphological as
well as physiological functions of a plant get affected (Kusaka et al. 2005; Shao et al.
2008). Drought stress can be injurious to physiological and metabolic events such as
turf quality, growth rate, root/shoot ratio, leaf carbon/nitrogen content, photosynthesis, transpiration, and stomatal conductance (Saud et al. 2014). Application of Si
ameliorates stressful drought conditions by elevating photosynthesis, total leaf water
content, chlorophyll content, and turf rate by 44%, 33%, 42%, and 44%, respectively
(Saud et al. 2014). It often results in disrupted water supply via the xylem, which
consequently results in lost turgor pressure and reduced stomatal closure (Taiz and
Zeiger 2006). It also convulses the photosynthetic framework via its association with
UV or visible rays (Garcia-Plazaola and Becerril 2000). The effectiveness of Si in
combating drought stress has been noted in many plants; for example, exogenous
2 Silicon: A Plant Nutritional “Non-Entity” for Mitigating Abiotic
23
Silicon and Abiotic Stresses
As per the literature, the important roles attributed to Si in plants include elevation in
growth, crop yield, and quality, photosynthesis, nitrogen (N 2 ) fixation as well as
protection against abiotic and biotic stresses (Balakhnina and Borkowska 2013;
Steiner et al. 2018; Malhotra and Kapoor 2019; Zargar et al. 2019; Ahanger et al.
2020; Singh et al. 2020). Interestingly, the abiotic stresses are the first and foremost
reason that besets the annual productivity rate. Abiotic stresses include salinity,
extreme temperature, UV-B radiation, heavy metal/metalloid toxicity, mechanical
injury, nutrient deficit, nutrient toxicity, and drought (Sharma et al. 2020). All these
stresses result in oxidative, osmotic as well as an ionic inconvenience in plants that
ultimately culminate into reactive oxygen species (ROS) accumulation, altered
metabolic and physiological processes (Sharma et al. 2020). This ultimately results
in hampered growth and net productivity which affect the farmer fields, farmer
pockets, and overall economy (Sharma et al. 2020).
A plethora of lab-scale, greenhouse-level, and field experiments have been
conducted that endorses the numerous benefits of silicon on the plants growing
under adverse conditions (Soundararajan et al. 2014; Manivannan et al. 2016;
Luyckx et al. 2017; Liu et al. 2019; Malhotra and Kapoor 2019; Zargar et al.
2019; Ahanger et al. 2020). It has also been deduced that it is not single but an
amalgamation of key mechanisms that alleviate stresses which include: (1) attunement of antioxidant systems and osmolytes for harmful ROS detoxification,
(2) immobilization or complex formation/co-precipitation or compartmentation of
noxious metal ions and enhanced uptake of nutrients, (3) modifying water as well as
nutrients uptake processes, (4) regulating expression of various genes, phytohormone biosynthesis, maintenance of osmotic potential, photosynthetic apparatus, and
gaseous exchange, and (5) formation of Si–cuticle double layer (Tripathi et al. 2016;
Etesami and Jeong 2018; Etesami and Jeong 2020; Souri et al. 2020) (Fig. 2.2).
2.4.1 Drought
Drought imposes a grave threat to plant population on earth as the morphological as
well as physiological functions of a plant get affected (Kusaka et al. 2005; Shao et al.
2008). Drought stress can be injurious to physiological and metabolic events such as
turf quality, growth rate, root/shoot ratio, leaf carbon/nitrogen content, photosynthesis, transpiration, and stomatal conductance (Saud et al. 2014). Application of Si
ameliorates stressful drought conditions by elevating photosynthesis, total leaf water
content, chlorophyll content, and turf rate by 44%, 33%, 42%, and 44%, respectively
(Saud et al. 2014). It often results in disrupted water supply via the xylem, which
consequently results in lost turgor pressure and reduced stomatal closure (Taiz and
Zeiger 2006). It also convulses the photosynthetic framework via its association with
UV or visible rays (Garcia-Plazaola and Becerril 2000). The effectiveness of Si in
combating drought stress has been noted in many plants; for example, exogenous
2 Silicon: A Plant Nutritional “Non-Entity” for Mitigating Abiotic
23