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

Abstract

Silicon (Si) is a beneficial nutrient for crop plants, and is gaining increased attention because of its involvement in regulation of abiotic stress tolerance. The present study was carried out to explore the underlying physiological and biochemical mechanisms of foliar Si-induced enhancement in wheat tolerance against cadmium (Cd) stress. Surface sterilized seeds of two wheat cultivars, viz., Inqalab-91 (sensitive) and Sahar-2006 (tolerant), were sown in plastic pots. Foliar application of Si (3 mM) was done at 20 days after sowing under control (−Cd) and Cd stress (25 mg kg −1 soil) conditions. Plants were harvested after 3 weeks of foliar spray, and data regarding morphological growth, oxidative metabolism, photosynthetic pigments, gas exchange attributes, metabolite accumulation, and ion homeostasis were recorded. The experimental treatments were arranged in completely randomized design with four replicates per treatment. Cadmium stress was found to significantly decrease the morphological growth, photosynthesis, and photosynthetic pigments in both wheat cultivars, while significantly increased malondialdehyde (MDA) content, hydrogen peroxide (H 2 O 2) content, and electrolyte leakage (EL) that triggered oxidative stress. The Cdinduced changes in superoxide dismutase (SOD), peroxidase (POD), catalase (CAT), ascorbate peroxidase (APX), glutathione S-transferase (GST), and glutathione reductase (GR) activities varied with cultivar and Si application. Plants treated with Si revealed better growth, higher accumulation of total soluble proteins, anthocyanins, total soluble sugar, flavonoids, and phenolics contents, and efficient antioxidant defense system as indicated by increased ascorbic acid and glutathione pools, and higher activities of SOD, POD, CAT, and APX particularly under Cd stress. Application of Si reduced Cd-mediated oxidative stress and increased photosynthetic pigments and net photosynthetic rate in both wheat cultivars. Further, Si application enhanced mineral ions in normal (−Cd) and Cd-stressed plants, and significantly decreased the Cd uptake. The Si-induced effects were more prominent in Sahar-2006 than that in Inqalab-91 for most of the studied traits, particularly under stress conditions. In short, foliar application of Si alleviates the adverse effects of Cd on wheat growth by strengthening antioxidant defense system, enhancing metabolite accumulation, improving plant nutrient status, and decreasing the Cd uptake.

Silicon Application Modulates Growth, Physio-Chemicals, and Antioxidants in Wheat (Triticum aestivum L.) Exposed to Different Cadmium Regimes

“…82 Silicon improved the photosynthetic pigments and protect them from oxidative injury by increasing the synthesis and accumulation of chlorophyll and carotenoid contents. 83,84 In the present study, Si application lessens the oxidative injury in wheat caused by Cd, which might have provoked the chlorophyll and carotenoid contents accumulation in wheat seedling (Table 4).…”

“…In addition, more Cd contents were accumulated in root of both cultivars than those in the shoot ( Figure 4 ). Thind et al (2020) 84 described that Si inhibited the uptake of Cd and decreased its transport in different plant tissues by chelating mechanism. Si being a non-essential nutrient for crop plants can affect plant growth and development in stressed 110 or normal conditions.…”

Role of exogenous-applied salicylic acid, zinc and glycine betaine to improve drought-tolerance in wheat during reproductive growth stages

“…Universally, the wheat crop is the primary vegetable protein source in the diet of humans, containing a higher protein content than other main grain crops such as maize and rice. The increasing population and food demands further necessitate the increase in wheat production to ensure social stability and future food security [ 2 , 3 ]. In China, wheat is the second-most important food crop after rice and the third-most important crop in total production overall, after maize and rice [ 4 ].…”

“…Drought causes various changes in crop plants through different morphological, physiological, and biochemical responses [ 11 – 13 ]. Many studies have reported that the defense system of antioxidant was increased through the synthesis of antioxidants such as ascorbate peroxidase (APX) and glutathione reductase (GR), and enzymatic antioxidants such as peroxidase (POD), catalase (CAT), and superoxide dismutase (SOD), which were stimulated to quench the ROS production in plants during drought stress [ 3 , 6 , 14 – 16 ]. Moreover, Datir et al [ 17 ] have reported that the antioxidant enzymes, free proline contents, GB accumulation, MDA, and H 2 O 2 contents were increased under drought induced by polyethylene glycol (PEG) in wheat cultivars.…”

Exogenous Oxalic Acid Protects Germinating Chickpea Seeds Against Cadmium Injury

“…The sources of environmental contamination by Cd are mainly anthropogenic, such as phosphate fertilizers, irrigation with wastewater, metal industries, and heating systems (Sohail et al 2019). Reduced growth, chlorosis, necrosis, phosphorus and nitrogen deficiency, and disturbance of photosynthetic metabolism are the prevalent Cd poisoning-related symptoms (El Rasafi et al 2020;Thind et al 2020). These signs are dependent on the species, the concentration of the metal in the culture medium, and the stage of plant development (Hussain et al 2015).…”