Microstructural changes in the fruit and pedicel of 'Wonhwang' oriental pear induced by exogenous gibberellins

- Exogenous gibberellin, which was treated at pedicel of pear fruit, promoted the growth in volume of fruit and pedicel.
- The increased size of the GA-treated fruits was dependent on increased cell expansion.
- Exogenous GA accelerated the development of pedicel via increasing in cell division.

This study was performed to investigate the anatomical reactions of oriental pear to exogenous gibberellins (GA). The development of fruits and pedicels, including the processes of cell division and expansion, at the direct GA application site was compared with that at distal sites. The growth of GA-treated fruits was accelerated approximately one month after treatment, and the differences in size between treatments were maintained until harvest. The final size of the pedicels did not differ between treatments, but the GA-treated pedicels attained their final size 20 days earlier than the non-treated pedicels due to the accelerated enlargement of the GA-treated pedicels shortly after treatment. The increased size of the GA-treated fruits appeared to be dependent on increased cell expansion, whereas the accelerated pedicel development appeared to be dependent on increased rates of cell division. In particular, the increase in the diameter of the GA- treated pedicels was primarily due to improvements in the sizes of xylem and phloem tissues as a result of acceleration of cell division. In addition, the effect of exogenous GA on the acceleration of pedicel development was concentrated at the initial stage of active cell division, and during this period, the sizes began to differ between the GA-treated and non-treated fruits. Thus, it appears that improvements in pedicel development, particularly the acceleration of the enlargement of xylem and phloem tissues, which are the direct passages underlying nutrient supply into fruit, is a result of increases in the sizes of GA-treated fruits.