Study on Cell Wall Composition, Fruit Quality and Tissue Structure of Hardened ‘Suli’ Pears (Pyrus bretschneideri Rehd)

Fruit hardening is a new condition in ‘Suli’ pear fruits that affects their commercial value. This study analyzed the cell wall composition, fruit quality and tissue structure of normal and hardened fruit. The results showed that the protopectin, cellulose and hemicellulose content of hardened fruit were not significantly different from normal fruit. However, in hardened fruit, the soluble pectin content was significantly lower compared to normal fruit, and the lignin content was significantly higher compared to normal fruit, especially in the hardened fruit top region. Hardened fruit also displayed significantly higher cellular lignin autofluorescence than normal fruit. Regarding fruit quality, the firmness and titratable acid content in the hardened fruit were significantly higher than in normal fruit, and the stone cell content in the hardened fruit was significantly higher than in normal fruit, especially in the hardened fruit top region. Fruit water, soluble solid and soluble sugar content in the hardened fruit were significantly lower compared to normal fruit. While observing the development of stone cells, the size and density of stone cells in hardened fruits rapidly increased at 24–34 days after flowering (DAF), especially in the hardened fruit top region. It was likely that a significant synthesis of lignin caused a rapid increase in stone cell density, leading to fruit hardening.