STUDIES OF THE "TREE FACTOR" THAT INHIBITS THE RIPENING OF ATTACHED APPLES

Five experiments were conducted to study the tree factor (TF), an unknown compound(s) that was reported to be synthesized in apple leaves and transported to fruits where it inhibits ripening (ethylene production). In these five experiments, apples ripened on the same dates when they received photosynthate from normal leaves and from leaves that were six weeks older than normal. Delay in ripening and fruit growth were positively correlated with leaf/fruit ratios on ringed limbs. Auxin (IAA), cytokinen (benzyladenine) and gibberellin (GA4 + 7) did not replace TF on ringed/deleafed limbs. In comparison with apples on normal limbs, apples attached to deleafed limbs grew more slowly but had similar ripening dates. Attached and detached apples initiated starch loss several days before EC, indicating TF may repress sequential transcription for many ripening enzymes, not just the enzymes associated with ethylene production.