Observation of the anatomical causes of fruit softening during growth and storage periods in ‘Wonhwang’ oriental pear (Pyrus pyrifolia)

• Fruits in the growth stage were softened primarily by cell expansion and subsequent widening of the IS.
• Rapid softening during storage at room temperature was due to empty spaces resulting from cell wall destruction.
• Fruits stored at low temperature softened continually due to IS widening by cell contractions.

The objective of this study was to investigate the anatomical causes of the softening of Wonhwang oriental pear by digitizing changes in cell size and intercellular space (IS). We attempted to identify differences affected by growth stage, storage conditions, and harvest timing. Fruit softening was a process caused by changes in cell size, IS widening, and the breaking of cell wall concatenation. Fruits in the growth stage were softened primarily by cell expansion and subsequent widening of the IS. For fruits stored at room temperature, softening proceeded very rapidly; the reason underlying rapid softening appeared to be the empty spaces created by cell wall destruction. For fruits stored at low temperature, rapid softening caused by the destruction of cell walls was delayed, but the fruits softened continually due to IS widening. Furthermore, cell size exhibited a positive correlation with firmness, which caused IS widening and softening of the fruits due to cell contraction. Thus, decreased cell size and widened IS caused softening under low-temperature conditions, and the relationship between softening and cell size was different than that observed during the growth stage.