Silicon and Its Application Methods Improve Physiological Traits and Antioxidants in Triticum aestivum (L.) Under Cadmium Stress

Abstract

Plants are exposed to various abiotic stressors in agricultural systems, especially cadmium (Cd) stress, which hinders plant growth and development. The current study was conducted to assess the protective role of silicon (Si) application in two methods and to identify the optimum method of Si application for wheat plants grown hydroponically under the same levels of Cd stress. For this purpose, we used two different silicon (Si; 1 mmol L −1 Na 2 SiO 3) application methods (i.e., root application and foliar spray) on growth, chlorophyll contents, cell membrane injury contents, enzymatic and non-enzymatic antioxidants, and membrane permeability contents of winter wheat (Triticum aestivum L.) against four levels of cadmium (Cd), normal, 50 μmol L −1 , 100 μmol L −1 , and 200 μmol L −1 , in 2-repeated greenhouse experiments. Results showed that Cd stress markedly affects growth, chlorophyll contents, and physiological traits and boosted up anti-oxidative defense system activity, osmoprotectants, and Cd contents. However, Si application as foliar or root induced reversibility of Cd toxic effects by significantly increasing growth, chlorophyll contents, membrane stability index, and Si contents and significantly reducing membrane injury contents measured as electrolytic leakage (EL) contents, lipid peroxidation measured as malondialdehyde (MDA) contents, and osmotic pressure measured as hydrogen peroxide (H 2 O 2) contents and increased in enzymatic and non-enzymatic anti-oxidative defense system's activity. Being an effective beneficial element, Si with the preference of root application improved leaf area, plant biomass, membrane characteristic, photosynthetic rate, and anti-oxidative defense system of wheat plants by alleviating Cd toxicity.

Physiological and Biochemical Bases of Foliar Silicon-Induced Alleviation of Cadmium Toxicity in Wheat

“…It has been reported that Cd stress decreased the value of C E because Rubisco C E is involved in the consumption of CO 2 in the Calvin cycle of photosynthesis (Bokhtiar et al 2012) and in this study; the values of C E were considerably decreased under Cd stress (Table 5). Previously, various researchers have documented the Cdinduced reduction in P n , T r , and g s in different field crops (Rahman et al 2020).…”

“…In the present study, the results of experiment showed that higher accumulation of ROS (e.g., H 2 O 2 ) significantly enhanced the lipid peroxidation rate (MDA content) and EL in wheat cultivars (Table 6). Previously, Cd stress-induced production of H 2 O 2 and MDA contents has been reported in many plant species including wheat (Rahman et al 2020), rapeseed (Hasanuzzaman et al 2017), and maize (Anjum et al 2016). Therefore, plants developed different enzymatic and non-enzymatic antioxidants to alleviate the adverse effects of Cd-induced oxidative damage.…”

“…Excessive Cd accumulation in plant tissues causes leaf rolling, growth decline, yield loss, and even plant death (Rahman et al 2020). From a physiological perspective, excessive Cd leads to plant oxidative stress, destroys cell membrane structure, disrupts absorption of water and mineral elements (Hussain et al 2020a), and reduces net photosynthetic rate (Fernández et al 2013;Rahman et al 2020).…”

“…Excessive Cd accumulation in plant tissues causes leaf rolling, growth decline, yield loss, and even plant death (Rahman et al 2020). From a physiological perspective, excessive Cd leads to plant oxidative stress, destroys cell membrane structure, disrupts absorption of water and mineral elements (Hussain et al 2020a), and reduces net photosynthetic rate (Fernández et al 2013;Rahman et al 2020). Excess amount of Cd influenced the plant growth and root morphology due to enhance production of reactive oxygen species (ROS), especially H 2 O 2 that damages cell membranes measured in the form of MDA, a byproduct of lipid peroxidation (Møller et al 2007).…”

“…Overproduction of ROS under stress conditions generates lipids peroxidation, increases membrane permeability, causes chlorophyll degradation, and damages the proteins, DNA, and RNA (Gratao et al 2015). To overcome the inhibitory effects of ROS, plants possess complex oxidative defense mechanism containing enzymatic antioxidants (APX, SOD, POD, and CAT) contents (Rahman et al 2020), and non-enzymatic antioxidant compounds (anthocyanins, ascorbic acid, carotenoids, α-tocopherols, reduced glutathione (GSH), flavonoids, and phenolics) to overcome Cd-induced oxidative injury (Gill and Tuteja 2010). The stress tolerance in plants strongly correlates with the enhanced activities/levels of antioxidants.…”