Silicon Supplementation Induces Physiological and Biochemical Changes That Assist Lettuce Salinity Tolerance
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ORIGINAL PAPER
Silicon Supplementation Induces Physiological and Biochemical Changes That Assist Lettuce Salinity Tolerance Hozano de Souza Lemos Neto 1 & Marcelo de Almeida Guimarães 1 & Rosilene Oliveira Mesquita 1 & Wallace Edelky Sousa Freitas 1 & Alexandre Bosco de Oliveira 1 & Nildo da Silva Dias 2 & Enéas Gomes-Filho 3 Received: 21 May 2020 / Accepted: 15 September 2020 # Springer Nature B.V. 2020
Abstract Little is known abou the effects of silicon on the physiological and biochemical characteristics of vegetables under salt stress. Our aim was to evaluate Silicon’s role as attenuator of negative effects of saline stress in lettuce plants. The experiment was carried out in a completely randomized design with four replicates in a a 3 × 2 factorial arrangement, three salinity levels (1.65, 3.65, 7.65 dS m− 1) with and without silicon (0 and 2 mM). Gas exchange, chlorophyll ‘a’ fluorescence, photosynthetic pigments, lipid peroxidation, hydrogen peroxide (H2O2) levels, enzymatic and non-enzymatic mechanisms and accumulation of inorganic ions were evaluated. Salinity increased the total chlorophyll and maintained a high Fv/Fm ratio (above 0.80). Silicon reduced gas exchange at severe salt stress. The activity of ascorbate peroxidase enzymes and guaiacol increased in high-salinity stress, which resulted in a lower content of H2O2 and lipid peroxidation. Si induced the reduction of antioxidant enzymes activity in severe stress. Na+ and Cl− ions increased with the saline water, while K+ and the K+/Na+ ratio decreased. The limited accumulation of silicon in lettuce leaf tissues has not been sufficient to induce physiological responses that lead to increased production under high-salinity conditions. Keywords Osmotic effect. Sodium silicate. Gas exchange. Antioxidant enzymes. Lactuca sativa L
1 Introduction It is estimated that 20% of the cultivated land and 33% of the irrigated areas in the world present salinity issues (Shahbaz and Ashraf 2013; Shrivastava and Kumar 2015). This scenario has become more worrisome once this condition tends to increase with the intensification of anthropic activities. Salinity reduces crops yield due the osmotic and ionic effects, causing the reduction of plant-water uptake. Furthermore, it causes toxicity due to the accumulation of Na+ and Cl− ions in the shoot part, affecting plant growth (Munns and Tester 2008; Ashraf 2009; Oliveira et al. 2013). * Hozano de Souza Lemos Neto [email protected] 1
Center for Agrarian Sciences, Department of Plant Science, Federal University of Ceará, Fortaleza, CE, Brazil
2
Center for Agrarian Sciences, Department of Agronomic and Forest Sciences, Federal Rural University of the Semiarid, 59.625900 Mossoró, RN, Brazil
3
Center of Science, Department of Biochemistry and Molecular Biology, Federal University of Ceará, Fortaleza, CE, Brazil
Salinity triggers oxidative stress produced by reactive oxygen species (ROS) such as superoxide radicals (°O2−), hydrogen peroxide (H2O2) and hydroxyl radical (°OH), which in excess are reactive and toxi
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