The free movement of14C-labelled organic compounds from intact apple seeds to growing fruitlets and shoots

Indole-3-acetic acid (IAA-1 14 C, IAA-2 14 C) and gamma-aminobutyric acid labelled with 14 C were applied in lanoline to the surface of intact seeds or inserted into seeds of growing apple fruitlets or to the cut surface of the pericarp. Their translocation in trees was checked by means of autoradiography or by a low background Geiger-Müller counter. Auxin applied to the top of intact seeds, or inserted into the seeds was translocated and distributed within the pericarp, spur tissues and shoots below. The translocation of gamma-aminobutyric acid from seeds suggests that the capacity of apple seeds for extensive interchange with the surrounding tissues of the fruit and the spur is more general than suspected. A much poorer or no translocation to the spur was found when radioactive compounds were applied to the cut surface of the pericarp, while the seeds were left untouched. The results suggest two mechanisms of metabolite translocation in the apple fruit: two-directional for seeds and one-directional for the pericarp.