Effect of exogenous silicon treatments on cell wall metabolism and textural properties of tomato fruits

•Exogenous Si application (1.2 mmol L−1) enhanced tomato fruit firmness by.•Si application inhibited cell wall enzyme activities.•Ethylene production was also reduced by Si application.•Exogenous Si treatment can improve tomato fruit quality and shelf-life. This study investigated the effects of exogenous silicon (Si) treatment on cell wall metabolism in tomato fruits. The experiment was conducted with ‘Jinfan502’ tomato (Solanum lycopersicum L.) as the test material, which was cultivated in substrates with foliar sprays of the following different concentrations of Si treatments: 0 mmol·L−1 (CK), 0.6 mmol·L−1 (T1), 1.2 mmol·L−1 (T2), and 1.8 mmol·L−1 (T3). To study the effects of the treatment on the mature green, breaker, and red ripening stages of tomato fruit cell wall components, cell wall metabolism-related enzyme activities, textural properties, and the impact of ethylene production during the red ripening stage were assessed. The results showed that the cell wall components and textural properties of the T2 treatment were significantly higher than those of the CK treatment in the green mature, breaker, and red ripening stages. Among them, at the red ripening stage of fruiting, the content of cell wall components in the T2 treatment was significantly improved, and the contents of protopectin, cellulose, hemicellulose, and expansin were increased by 6.29 %, 10.04 %, 2.52 %, and 3.95 %, respectively, relative to the CK treatment; the firmness of the fruit was also significantly increased, by 13.23 %, compared with the CK treatment. Cell-wall-metabolism-related enzyme activity was significantly lower in the T2 treatment than in the CK treatment at the green mature, breaker, and red ripening stages. When Si (T2) was applied during the red ripening stage, the activities of cell wall metabolism-related enzymes were significantly inhibited; compared to the CK treatment, the activities of pectinase (PE), polygalacturonase (PG), pectin methylesterase (PME), β-galactosidase (β-Gal), lipoxygenase (LOX), pectin lyase (PL), and cellulase (CL) were reduced by 16.34 %, 19.37 %, 28.07 %, 10.73 %, 19.86 %, 8.47 %, and 6.53 %, respectively. Furthermore, the ethylene content of the red ripened fruits under the T2 treatment was significantly reduced by 21.59 % compared to the CK treatment. In addition, multiple sets of significant or extremely significant negative correlations existed among ethylene, cell wall components, and textural properties at red ripening stage. F