Silicon-Mediated Enhancement of Heavy Metal Tolerance in Rice at Different Growth Stages

Abstract

Silicon (Si) plays important roles in alleviating heavy metal stress in rice plants. Here we investigated the physiological response of rice at different growth stages under the silicon-induced mitigation of cadmium (Cd) and zinc (Zn) toxicity. Si treatment increased the dry weight of shoots and roots and reduced the Cd and Zn concentrations in roots, stems, leaves and grains. Under the stress of exposure to Cd and Zn, photosynthetic parameters including the chlorophyll content and chlorophyll fluorescence decreased, while the membrane permeability and malondialdehyde (MDA) increased. Catalase (CAT) and peroxidase (POD) activities increased under heavy metals stress, but superoxide dismutase (SOD) activities decreased. The magnitude of these Cd- and Zn-induced changes was mitigated by Si-addition at different growth stages. The available Cd concentration increased in the soil but significantly decreased in the shoots, which suggested that Si treatment prevents Cd accumulation through internal mechanisms by limiting Cd2+ uptake by the roots. Overall, the phenomena of Si-mediated alleviation of Cd and excess Zn toxicity in two rice cultivars could be due to the limitation of metal uptake and transport, resulting in an improvement in cell membrane integrity, photosynthetic performance and anti-oxidative enzyme activities after Si treatment.

Silicon-induced thermotolerance in Solanum lycopersicum L. via activation of antioxidant system, heat shock proteins, and endogenous phytohormones

“…Plants have evolved an effective antioxidant system using POD, CAT, SOD, PPO, and APX enzymes to eliminate stress-induced excess ROS, thereby protecting the cells from the deleterious effects of oxidation reactions [81]. CAT, APX, and POD antioxidants are known for the dismutation of hydrogen peroxide to water and molecular oxygen in cells [82], as well as the elimination of stress-induced ROS directly or indirectly via the production of ascorbate and glutathione [83].…”

Cadmium Uptake by Wheat (Triticum aestivum L.): An Overview

“…The Si is a useful and probably important component for plants and has an essential role in plant growth and development [75]. The Si may control nutrient relationships in plants grown under environmental hazards [76].…”

“…The Si may control nutrient relationships in plants grown under environmental hazards [76]. Additionally, considerable evidence suggests that the utilization of Si in soils may alleviate Zn or Cd toxicity in various plant species [75]. Ismael et al [61] stated that applying Se to plants under Cd stress may reduce the ethylene level and increase proline accumulation; this method may also increase the activity of glutathione peroxidase and glutathione reductase which initially relieves Cd-induced oxidative stress.…”

Silicon and Its Application Methods Improve Physiological Traits and Antioxidants in Triticum aestivum (L.) Under Cadmium Stress

“…Another group of researchers who used Si as root application reported that Si in root application could alleviate heavy metal (HM) stress more efficiently than Si foliar-application due to (1) decreased HM absorption from roots to shoots (Dong et al 2019), (2) enhanced HM binding with root cell walls and delimited their apoplastic transport (Huang et al 2018), and (3) coprecipitate with HMs to minimize biological active HM concentration in soil (Lu et al 2017).…”