Temperature is a key environmental factor that influences plant growth. Low temperatures reduce crop yields, while silicon and potassium help strengthen plants’ resistance to environmental stresses. The ameliorating effects of the foliar application of potassium silicate (K2SiO3) on the freezing-stressed (zero (control), -12, -20, and −25°C) barley plants at two stress exposure durations (SED; 2 and 5 h) were investigated. The results showed that when the temperature decreased to -20°C, plant survival rate decreased; however, K2SiO3 increased plant survival and improved leaf water status at temperatures up to -12°C. K2SiO3 also reduced malondialdehyde (MDA) content and electrolyte leakage (EL), and improved cell membrane integrity. The highest H2O2 activity was recorded at -20°C under the control at 2 h, while K2SiO3 at -12°C decreased H2O2 activity. The electron transport rate (ETR) increased over time by K2SiO3, and at 96 h of the recovery period, K2SiO3-treated plants showed ~ 47 times higher ETR than the control. The PSII potential (Fv’/Fm’) and operational (Fq’/Fm’) efficiencies were higher in the K2SiO3-treated plants than in the control. The results of principal component analysis (PCA) showed that flavonoid content, chlorophyll a and b, H2O2, total phenols, root and leaf EL, and Fv’/Fm’ were most correlated with the first component and plant survival, catalase and ascorbate peroxidase activity, dry weight, leaf relative water content, proline, and MDA with the second component. The results of cluster analysis showed a close relationship between the activities of antioxidant enzymes and the photosynthetic pigments. In general, K2SiO3 can increase the tolerance of barley plants to freezing stress, especially at lower temperatures and longer SED. These analyses can be beneficial in developing management strategies to improve plant resistance to freezing stress, including the application of K2SiO3.

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