Differences in cell proliferation and enlargement between seeded and seedless grape berries induced parthenocarpically by gibberellin

Abstract

SummaryA comparative study was conducted of cell proliferation and enlargement in seeded and seedless ‘Delaware’ grape berries induced parthenocarpically by pre-bloom application of gibberellin A3. Using paraffin-celloidin thin sections taken from the equatorial region of berry, number of cell layers and cells, and cell size were measured in the inner wall, outer wall parenchyma, subepidermis and epidermis directly by microscope or using microphotography. In the seedless berry, cell division and enlargement proceeded simultaneously in all tissues after post-bloom application of gibberellin A3. By then, in the seeded berry, cell division in the tissues, with the exception of the epidermis, was nearly complete. The cell numbers in epidermis and subepidermis collenchyma were fewer in the seedless berry than in the seeded berry. On the other hand, the number of parenchymatous cells in the outer wall of the seedless berry was approximately 1.4 times that found in the seeded berry. Cell enlargement rate was higher in the seedless berry than in the seeded berry, in all tissues. The cells in the outer wall parenchyma and the inner wall of the seedless berry were larger tangentially and radially, respectively, than those in the seeded berry. These results indicate that development of the seedless berry induced by application of gibberellin A3 follows quite a different course of cell division and enlargement when compared with the seeded berry.