Citation: Singh, P.; Kumar, V.; Sharma, J.; Saini, S.; Sharma, P.; Kumar, S.; Sinhmar, Y.; Kumar, D.; Sharma, A. Silicon Supplementation Alleviates the Salinity Stress in Wheat Plants by Enhancing the Plant Water Status, Photosynthetic Pigments, Proline Content and Antioxidant Enzyme Activities. Plants 2022, 11, 2525. https://doi.org/10.3390/ plants11192525 Academic Editors: Ricardo Aroca, Doan Trung Luu, Janusz J. Zwiazek and Gabriela Amodeo Received: 5 September 2022 Accepted: 21 September 2022 Published: 26 September 2022 Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affil- iations. Copyright: © 2022 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/). plants Article Silicon Supplementation Alleviates the Salinity Stress in Wheat Plants by Enhancing the Plant Water Status, Photosynthetic Pigments, Proline Content and Antioxidant Enzyme Activities Pooja Singh 1 , Vikram Kumar 1 , Jyoti Sharma 1 , Sakshi Saini 1 , Priyanka Sharma 1 , Sandeep Kumar 2 , Yogesh Sinhmar 3 , Dhirendra Kumar 4 and Asha Sharma 1, * 1 Department of Botany, Maharshi Dayanand University, Rohtak 124001, Haryana, India 2 Department of Botany, Baba Mastnath University, Rohtak 124001, Haryana, India 3 Department of Botany, Kurukshetra University, Kurukshetra 136119, Haryana, India 4 Department of Botany, Chaudhary Bansi Lal University, Bhiwani 127021, Haryana, India * Correspondence: drasha.botany@mdurohtak.ac.in Abstract: Silicon (Si) is the most abundant element on earth after oxygen and is very important for plant growth under stress conditions. In the present study, we inspected the role of Si in the mitigation of the negative effect of salt stress at three concentrations (40 mM, 80 mM, and 120 mM NaCl) in two wheat varieties (KRL-210 and WH-1105) with or without Si (0 mM and 2 mM) treatment. Our results showed that photosynthetic pigments, chlorophyll stability index, relative water content, protein content, and carbohydrate content were reduced at all three salt stress concentrations in both wheat varieties. Moreover, lipid peroxidation, proline content, phenol content, and electrolyte leakage significantly increased under salinity stress. The antioxidant enzyme activities, like catalase and peroxidase, were significantly enhanced under salinity in both leaves and roots; however, SOD activity was drastically decreased under salt stress in both leaves and roots. These negative effects of salinity were more pronounced in WH-1105, as KRL-210 is a salt-tolerant wheat variety. On the other hand, supplementation of Si improved the photosynthetic pigments, relative water, protein, and carbohydrate contents in both varieties. In addition, proline content, MDA content, and electrolyte leakage were shown to decline following Si application under salt stress. It was found that applying Si enhanced the antioxidant enzyme activities under stress conditions. Si showed better results in WH-1105 than in KRL-210. Furthermore, Si was found to be more effective at a salt concentration of 120 mM compared to low salt concentrations (40 mM, 80 mM), indicating that it significantly improved plant growth under stressed conditions. Our experimental findings will open a new area of research in Si application for the identification and implication of novel genes involved in enhancing salinity tolerance. Keywords: wheat; silicon; salt stress; KRL-210; WH-1105; phenol content; electrolyte leakage 1. Introduction Wheat (Triticum aestivum) is among the major staple crops produced worldwide, mainly for human consumption [1]. Due to the increasing population, the world is highly dependent on wheat for food. Globally, wheat provides approximately 55% of the carbo- hydrates and 20% of the calories consumed on a daily basis [2]. Various environmental factors affect crop production, with salinity being one of them. Salinity is a crucial form of abiotic stress that badly affects food crops [3,4]. Due to human activities and climate change, salinity affects around one fifth of cultivated areas and a third of all irrigated agricultural land area on which staple crops such as wheat are grown; this rate is increasing steadily [5]. However, research is ongoing to improve crop production under these stresses. Salt stress causes physiological, biochemical, and metabolic alterations in plants, resulting in poor crop production. Under high-stress conditions, the water uptake is restricted in the Plants 2022, 11, 2525. https://doi.org/10.3390/plants11192525 https://www.mdpi.com/journal/plants