Silicon-Induced Tolerance against Arsenic Toxicity by Activating Physiological, Anatomical and Biochemical Regulation in Phoenix dactylifera (Date Palm)

Taimoor Khan; Saqib Bilal; Sajjad Asaf; Safiya Salim Alamri; Muhammad Imran; Abdul Latif Khan; Ahmed Al-Rawahi; In-Jung Lee; Ahmed Al-Harrasi

doi:10.3390/plants11172263

Silicon-Induced Tolerance against Arsenic Toxicity by Activating Physiological, Anatomical and Biochemical Regulation in Phoenix dactylifera (Date Palm)

Plants (Basel). 2022 Aug 31;11(17):2263. doi: 10.3390/plants11172263.

Authors

Taimoor Khan¹, Saqib Bilal¹, Sajjad Asaf¹, Safiya Salim Alamri¹, Muhammad Imran², Abdul Latif Khan³, Ahmed Al-Rawahi¹, In-Jung Lee², Ahmed Al-Harrasi¹

Affiliations

¹ Natural & Medical Sciences Research Center, University of Nizwa, Nizwa 616, Oman.
² Division of Plant Biosciences, School of Applied Biosciences, College of Agriculture & Life Science, Kyungpook National University, 80 Dahak-ro, Buk-gu, Daegu 41566, Korea.
³ Department of Engineering Technology, University of Houston, Sugar Land, TX 77479, USA.

Abstract

Arsenic is a toxic metal abundantly present in agricultural, industrial, and pesticide effluents. To overcome arsenic toxicity and ensure safety for plant growth, silicon (Si) can play a significant role in its mitigation. Here, we aim to investigate the influence of silicon on date palm under arsenic toxicity by screening antioxidants accumulation, hormonal modulation, and the expression profile of abiotic stress-related genes. The results showed that arsenic exposure (As: 1.0 mM) significantly retarded growth attributes (shoot length, root length, fresh weight), reduced photosynthetic pigments, and raised reactive species levels. Contrarily, exogenous application of Si (Na₂SiO₃) to date palm roots strongly influenced stress mitigation by limiting the translocation of arsenic into roots and shoots as compared with the arsenic sole application. Furthermore, an enhanced accumulation of polyphenols (48%) and increased antioxidant activities (POD: 50%, PPO: 75%, GSH: 26.1%, CAT: 51%) resulted in a significant decrease in superoxide anion (O₂^•-: 58%) and lipid peroxidation (MDA: 1.7-fold), in silicon-treated plants, compared with control and arsenic-treated plants. The Si application also reduced the endogenous abscisic acid (ABA: 38%) under normal conditions, and salicylic acid (SA: 52%) and jasmonic acid levels (JA: 62%) under stress conditions as compared with control and arsenic. Interestingly, the genes; zeaxanthin epoxidase (ZEP) and 9-cis-epoxycarotenoid dioxygenase (NCED-1) involved in ABA biosynthesis were upregulated by silicon under arsenic stress. Likewise, Si application also upregulated gene expression of plant plasma membrane ATPase (PMMA-4), aluminum-activated malate transporter (ALMT) responsible for maintaining cellular physiology, stomatal conductance, and short-chain dehydrogenases/reductases (SDR) involved in nutrients translocation. Hence, the study demonstrates the remarkable role of silicon in supporting growth and inducing arsenic tolerance by increasing antioxidant activities and endogenous hormones in date palm. The outcomes of our study can be employed in further studies to better understand arsenic tolerance and decode mechanism.

Keywords: ABA; SA; antioxidants system; arsenic toxicity; date palm; organic acids; silicon.

Grants and funding

This research work was supported by internal research fund of University of Nizwa and National Research Foundation of Korea (NRF)grant funded by the Korean Government (MSIT) (No.2022R1A2C1008993).