Abstract
BackgroundSilicon (Si) application has been known to enhance the tolerance of plants against abiotic stresses. However, the protective mechanism of Si under heavy metals contamination is poorly understood. The aim of this study was to assess the role of Si in counteracting toxicity due to cadmium (Cd) and copper (Cu) in rice plants (Oryza sativa).ResultsSi significantly improved the growth and biomass of rice plants and reduced the toxic effects of Cd/Cu after different stress periods. Si treatment ameliorated root function and structure compared with non-treated rice plants, which suffered severe root damage. In the presence of Si, the Cd/Cu concentration was significantly lower in rice plants, and there was also a reduction in lipid peroxidation and fatty acid desaturation in plant tissues. The reduced uptake of metals in the roots modulated the signaling of phytohormones involved in responses to stress and host defense, such as abscisic acid, jasmonic acid, and salicylic acid. Furthermore, the low concentration of metals significantly down regulated the mRNA expression of enzymes encoding heavy metal transporters (OsHMA2 and OsHMA3) in Si-metal-treated rice plants. Genes responsible for Si transport (OsLSi1 and OsLSi2), showed a significant up-regulation of mRNA expression with Si treatment in rice plants.ConclusionThe present study supports the active role of Si in the regulation of stresses from heavy metal exposure through changes in root morphology.
Highlights
Silicon (Si) application has been known to enhance the tolerance of plants against abiotic stresses
Si improves rice plant growth under heavy metal exposure The effect of Si and heavy metal (Cu and Cd) treatments on rice plant growth was assessed after different time points (1, 5, and 10 days after treatment – Day after treatment (DAT); Figure 1)
The results showed that Si application significantly increased plant growth attributes as compared with the control plants under normal growth conditions
Summary
Silicon (Si) application has been known to enhance the tolerance of plants against abiotic stresses. Heavy metal toxicity retards plant growth by marginalizing the cellular functions of proteins, lipids, and elemental components of thylakoid membranes. Cadmium (Cd) and copper (Cu) have been known to hinder the growth of crop. The uptake of heavy metals is influenced by metaltransporting transmembrane proteins, including Heavy Metal ATPases (HMAs), Low-affinity Cation Transporters (LCTs) and Iron-regulated Transporters (IRTs) [7,11,12]. These commonly known metal transport genes are located throughout the structure of plant which translocate a diverse set of metal ions [13,14]. Previous studies in Arabidopsis thaliana have confirmed the physiological functions of the HMAs (AtHMA1, AtHMA2, AtHMA3, and AtHMA4) that is to detoxify zinc from chloroplast and signal Cd accumulation in the vacuoles and plasma membrane [15,16,17,18]
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