This investigation was carried out during two successive seasons of 1990/91
and 1991/92 to study the relationship between the anatomical structure of rachis &
pedicels as well as berry shattering of Thomoson Seedless grape clusters during
harvest and handling as affected by gibberellic acid. The study included 5 treatments and the control. Grape clusters were
dipped in 10. 20. 30. 40 and 50 ppm GAJ solutions before nowering and after truit-set. All G~ treatments induced berry shattering. since the percentage increased
with increasing G~ concentration. Also GA3 treatments increased the pedicel
diameter and number of secondary xylem cells. The higher levels of GA3 at 40 and 50
ppm induced more diameter and number of secondary cells along the radial rows.
lignin content in rachis and pedicels also increased significantly specially with G~ at
50 ppm.GAl at all concentrations used increased cellulouse content in the rachis and
pedicels, the increase was proportional to the level of GA3 applied. From this study it is concluded that using low concentrations of GAJ is
recommended to avoid berry shattering at harvest and during handling_ Thus, lower
concentrations of GAJ at 10-20 ppm can be used for elongation. while 30 ppm is used
tor increasing berry size.