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IntroductionProline is a proteinogenic amino acid, highly essential for various vital metabolic processes within the plant tissues. It is naturally present in plants, microbes, and animals (

IntroductionAbiotic stresses drastically affect crops by minimizing yield. Plants face many distinctive abiotic stresses at different stages of plant growth and development. Among these stresses, salinity is prejudicious, limiting plant growth and productivity. Salt stress causes various deleterious effects on morphological, physiological, biochemical, and nutritional attributes. The formation of reactive oxygen species (ROS) is the significant consequence of salt stress. The major ROS comprise hydroxyl ( . OH), superoxide (O 2 .-), and hydrogen peroxide (H 2 O 2 ). The high ratios of ROS are responsible for lipid peroxidation (LPO) of tissues and cause deterioration of proteins, green pigments, and DNA (Schutzendubel and Polle, 2002). However, nature has equipped all vegetations with a defensive antioxidant system to counter the oxidative damage caused by ROS (Apel and Hirt, 2004). Plant growth under saline conditions is highly associated with its antioxidant activities, i.e. superoxide peroxidase (SOD), peroxidase (POD), catalase (CAT), ascorbate peroxidase (APX), guaiacol peroxidase (GPX), and glutathione reductase (GTR) activities. High antioxidant activities will inhibit LPO by eliminating the ROS.Silicon (Si) is an excellent growth promoting agent. Silicon is reported to increase plant growth and stimulate productivity in various crop plants. Si application strengthened the plant biomass, height, and productivity under different stressed conditions (Ahmad et al., 2007). It also triggers growth by providing strength and extensibility to plant cells. It strengthens the endoderm of the mature basal cells and improves the extensibility of apical cells of the roots; thus Si contributes to a strong, extensive, and deep root system. However, it is also a vital element that has an excellent tolerance enhancing potential against abiotic Abstract: A pot culture study was conducted to assess the ameliorative effect of silicon, Melia azadirachta leaf extract, and sugar beet root extract, each applied individually or in different combinations, on salinity-induced detrimental effects in pea (Pisum sativum L.). Salinity markedly inhibited the growth, various gas exchange attributes, total phenol contents, membrane stability index, and productivity. On the other hand, lipid peroxidation, electrolyte leakage, H 2 O 2 content, antioxidant activities, and leaf free proline and glycinebetaine contents were significantly enhanced by salinity. However, exogenously applied Si and phyto-extracts markedly alleviated the salinity-induced drastic effects on growth, gas exchange attributes, and productivity. Both phyto-extracts supplemented with silicon gave highly salinity mitigating effects by markedly improving growth, gas exchange attributes, enzymatic activities, osmolytes, and yield. The phyto-extracts and Si suppressed lipid peroxidation, electrolyte leakage, and H 2 O 2 content by strengthening the enzymatic and nonenzymatic (proline and glycinebetaine) antioxidant defense system. The phyto-extracts and Si application also che...

A pot culture study was performed to evaluate the differences between salt-stressed pea (Pisum sativum L.) plants of tolerant (Climax and Samarina Zard) and sensitive (Ambassidar and PF-400) genotypes, and to determine whether treatment with 24-epibrassinolide (EBL) could enhance the accumulation of osmolytes and antioxidant activity and thereby induce tolerance in saltstressed plants. Three-week-old seedlings were subjected to +NaCl (5 dS m -1 ) and -NaCl conditions (0 dS m -1 ). After 4 days of salt stress, the plants were sprayed with Milli-Q water or EBL (0.125 mg L -1 ). The plants were sampled at 32 days after sowing and at the final maturity stage. Half-strength Hoagland solution was used as the nutrient medium. Both the tolerant and sensitive plants subjected to saline condition showed decreases in germination percentage, embryo axis length, plant fresh/dry biomass, leaf area, chlorophyll content, relative water content (RWC), photosynthesis, rubisco content, rubisco activity, stomatal conductance, number of stomata, stomatal size, number of epidermal cells, and yield attributes and increases in lipid peroxidation, total phenolics content, proline content, glycine betaine content, total amino acids content, total soluble sugars content, sucrose content, sucrose phosphate synthase activity, sucrose synthase activity, and activities of antioxidant enzymes (superoxide dismutase, peroxidase, catalase, ascorbate peroxidase, and guaiacol peroxidase). Salt stress had a less deleterious effect on Climax and Samarina Zard than on Ambassidar and PF-400. The foliar application of EBL mitigated the deleterious effects of NaCl by improving growth, productivity, and gas exchange attributes and by further enhancing the concentrations of the above osmolytes and antioxidants, particularly in the tolerant genotypes. The enhanced concentrations of osmolytes and antioxidants may have induced salt tolerance in the plants subjected to saline conditions, resulting in improved growth, gas exchange attributes, and yield.

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