The effect of pectic oligomers (OG) on ethylene biosynthesis, electrolyte leakage (EL), and CO2 production was studied in discs excised from zucchini fruit (Cucurbita pepo L.) and stored at 20 or 2.5degreesC. At 20degreesC, OG enhanced ethylene biosynthesis and had a transient effect on decreasing EL, but showed little effect on respiratory rate; both the amount and size of the oligomer were important in changing both ethylene synthesis and EL. At 2.5degreesC, OG increased both ethylene biosynthesis and respiratory rate with a maximum effect at 100 mug of oligomer and peaking at 6 h; shorter oligomers demonstrated an even greater effect on ethylene biosynthesis, but differences were smaller in respiratory rate. EL at 2.5degreesC was affected most by 1 mug of OG and by monomeric galacturonic acid, with transient increases that peaked at 8 h. We suggest a signaling role for OG in the early steps of cold acclimation or chilling injury. (C) 2002 Elsevier Science.