An Ultrastructural Evaluation of the Relationship of Embryo/Endosperm Abortion to Apple Fruit Abscission During the Post-Bloom Period1

Comparisons of seed tissues from persistent and potential drop apple fruit (‘Golden Delicious’) 3 weeks after full bloom suggested that fruit commitment to abscise (determined by a reduced rate of fruit enlargement between 16 and 21 days after full bloom) preceded ultrastructural evidence of degenerative or functional changes in embryo or endosperm tissue. The results do not support the concept of ‘embryo abortion’ as a causal mechanism in natural fruit abscission during post-bloom.