Silicon influenced ripening metabolism and improved fruit quality traits in apples

The benefits of silicon against abiotic stress in different annual plant species have been described in many studies, however the regulation of ripening of fruit tree crops by silicon remains largely uncharacterized. Therefore, the present study aimed to explore the impact of foliar silicon application in the apple (cv. 'Fuji') fruit ripening traits along with the effect of silicon in the nutrient and metabolic changes in the fully expanded leaves, annual shoots, fruit outer pericarp (peel) and fruit mesocarp (skin) tissues. Data indicated that fruit firmness and apple peel color attributes, such as redness (a*) and percentage of red-blushed surface were induced by silicon application. Moreover, several fruit ripening traits, such as titratable acidity, soluble solid content and respiration rate were unaffected by silicon. Endogenous silicon level in leaves shoots and peel tissues were increased by exogenously applied silicon while several elements (i.e., P, Mg, Mn, Fe and Cu) were altered in the tested tissues that exposed to silicon. In addition, silicon increased the accumulation of total phenolic and total anthocyanin compounds in the various apple tissues. The level of various primary metabolites including sorbitol, fructose, maltose cellobiose, malic acid, phosphoric acid and gluconic acid was also notably affected by silicon in a tissue-specific manner. Overall, this study provides a valuable resource for future research, aiming in the elucidation of the role of silicon in fruit tree physiology.