Sodium metasilicate solution enhances drought stress tolerance by improving physiological characteristics in apple stocks

Abstract

Abstract Sodium metasilicate solution treatment contributes to improved plant tolerance to drought stress. In this study, pot experiments were conducted to compare the effect of sodium metasilicate solution on Malus halliana and Malus hupehensis seedlings under drought stress. Principal component analysis (PCA) was used to evaluate the effects of sodium metasilicate solutions on gas exchange, fluorescence, and physiological characteristics. Forty days after transplantation, the control (75% field capacity (FC)) and treatment 1 (50% FC) seedlings were sprayed with distilled water, and the other treatment (50% FC) seedlings were sprayed with a sodium metasilicate (Na2SiO3·9H2O) solution at different concentrations. The results showed that the growth of M. halliana and M. hupehensis was inhibited when exposed to drought stress. This adverse effect was reversed by applying sodium metasilicate solution, and there was a significant concentration effect. Compared to the control, sodium metasilicate solution increased the proline (Pro) content. At the same time, the decrease in the SPAD values, net photosynthetic rate (P n), stomatal conductance (G s), transpiration rate (T r), initial fluorescence (F 0), maximum fluorescence (F m), photochemical efficiency (F v/F m), electron transfer rate (ETR), and superoxide dismutase (SOD) activity were effectively controlled. The increase in intercellular CO2 concentration (C i) and malondialdehyde (MDA) content was also restricted. Additionally, the PCA showed that the first principal component of M. halliana accounted for 80.42% variance, contributed by P n, T r, G s, Pro, SOD, F v/F m, and ETR. The first principal component of M. hupehensis accounted for 69.72% and mainly contained P n, SPAD, and F v/F m index information. The PCA evaluation showed that the effect of sodium metasilicate solution on M. halliana and M. hupehensis seedlings under drought stress was most significant (p < 0.05) at concentrations of 2.5 and 3.75 mM·L−1, respectively.