- Spermidine application to young developing peach fruits leads to a slowing down of ripening by impairing ripening-related ethylene and auxin metabolism and signaling. Torrigiani, P., Bressanin, D., Ruiz, K.B., Tadiello, A., Trainotti, L., Bonghi, C., Ziosi, V., Costa, G. Physiol. Plant (2012)