The Impact of Silicon on the Morphological and Physio-Chemical Characteristics of Calendula officinalis Exposed to Arsenic-Induced Toxicity
Huifen Cao, A. Ghorbanpour, Abazar Ghorbani, Mahvash Zargar, Seyed Mehdi Razavi
Abstract
Arsenic (As), a hazardous metal, is widely found in industrial and agricultural wastewater, as well as in pesticides. Silicon (Si) can be crucial in mitigating As toxicity. This research aimed to investigate 0.5 and 1 mM Si treatments on Calendula officinalis under As toxicity (25 and 50 µM). As treatments significantly reduced growth characteristics, photosynthesis (Fv/Fm and photosynthetic pigments), and the accumulation of some essential elements (N, Ca, P, Zn, K, Mn, and Fe), while increasing the levels of H2O2, $${\text{O}}_{2}^{ - }$$ , and MG. Contrarily, the external application of Si to C. officinalis L. restricted As accumulation, leading to less oxidative damage and better accumulation of elements and photosynthesis. Additionally, the levels of sulfur-containing compounds (GSH, NPTs, PCs, and cysteine) increased, along with enhanced Gly I and Gly II activities and antioxidant activities (CAT, SOD, GR, and APX), leading to a notable drop in free toxic radicals and lipid peroxidation in As-stressed plants. Furthermore, Si supplementation regulated the thiol metabolism enzyme glutathione-S-transferase and improved cysteine synthesis by increasing the activities of serine acetyltransferase, cysteine synthase (CS), and adenylyl sulfate reductase. Therefore, this study showcases the significant contribution of Si in promoting growth, facilitating photosynthesis, and fostering As tolerance through various pathways, such as enhancing antioxidant activities, the glyoxalase system, non-enzymatic and enzymatic sulfur metabolism, reducing As uptake, and increasing the accumulation of essential elements.