Abstract
Silicon (Si) is the second most abundant element in soil, where its availability to plants can exhilarate to 10% of total dry weight of the plant. Si accumulation/transport occurs in the upward direction, and has been identified in several crop plants. Si application has been known to ameliorate plant growth and development during normal and stressful conditions over past two-decades. During abiotic (salinity, drought, thermal, and heavy metal etc) stress, one of the immediate responses by plant is the generation of reactive oxygen species (ROS), such as singlet oxygen (1O2), superoxide (), hydrogen peroxide (H2O2), and hydroxyl radicals (OH), which cause severe damage to the cell structure, organelles, and functions. To alleviate and repair this damage, plants have developed a complex antioxidant system to maintain homeostasis through non-enzymatic (carotenoids, tocopherols, ascorbate, and glutathione) and enzymatic antioxidants [superoxide dismutase (SOD), catalase (CAT), and ascorbate peroxidase (APX)]. To this end, the exogenous application of Si has been found to induce stress tolerance by regulating the generation of ROS, reducing electrolytic leakage, and malondialdehyde (MDA) contents, and immobilizing and reducing the uptake of toxic ions like Na, under stressful conditions. However, the interaction of Si and plant antioxidant enzyme system remains poorly understood, and further in-depth analyses at the transcriptomic level are needed to understand the mechanisms responsible for the Si-mediated regulation of stress responses.
Highlights
Silicon (Si) has a strong affinity with oxygen; it usually exists as silica (SiO2) under natural conditions (Ma and Takahashi, 2002)
According to Kim et al (2014c), the application of Si in rice plants under salinity significantly decreased the activities of non-enzymatic MDA and enzymatic antioxidants POD, PPO, and CAT on the other hands, Torabi et al (2015) observed that when they applied Si to borage plant, superoxide dismutase (SOD) activity was significantly increased in Si treatment but activity of CAT and ascorbate peroxidase (APX) was slightly decreased in Si application (Table 1)
The Si application shows varying response to reactive oxygen species (ROS) scavenging by activating the defense system plants
Summary
Silicon (Si) has a strong affinity with oxygen; it usually exists as silica (SiO2) under natural conditions (Ma and Takahashi, 2002). Exogenously Si can improve the ability of ROS scavenging by regulation of antioxidants enzyme activity (Torabi et al, 2015; Kim et al, 2016; Tripathi et al, 2017).
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