TRANSPORT OF C-14 IAA FROM LEAVES AND SHOOTS TO DIFFERENT FRUIT PARTS

Transport of C-14-IAA was studied in apple spurs of a 20-year-old McIn tosh with one fruit and one shoot. Water solutions of IAA were applied to intact, pricked or scratched leaf blades, to decapitated shoots or to petioles (leaf-blade removed) at the end of June, July and AugUst. C-14-IAA (in an unknown form) was transported from intact leaves and shoots to pedicel, pericarp and seeds. Radioactivity of the pedicels i ncreased every month while that of seeds reached maximum at the end of July and then markedly decreased in August. Total radioactivity of wh ole fruit doubled, at least, with every month due to enlargement of th e pericarp. Pedicels deprived of fruits had their retention prolonged on spurs with leaves or shoots treated with 1% IAA in lanoline. It is assumed that auxin delivered from shoots or still growing leaves at th e time of its deficiency in seeds, restrains fruits from premature dro pping. At the same time seeds seem to be protected by a regulatory sys tem in pedicel against too massive flow of auxin from outside.