TIME COURSE STUDY OF THERMOREGULATION IN ETHYLENE BIOSYNTHESIS AND RIPENING OF "HAYWARD" KIWIFRUIT INDUCED BY PROPYLENE

Individual "Hayward" kiwifruit fitted with hypodermic needles were treated with propylene (130 μl/l) in a continuous flow-through system at 20°, 0°, 20°&rarrow;0°, 0°&rarrow;20°, 20°&rarrow;0°&rarrow;20°C and internal ethylene concentration was measured repeatedly from he same fruit during a 330 hrs storage period. In a parallel experiment, fruit ripening (firmeness and SSC), internal ethylene concentration, ACC and EFE activity were measured in fruit exposed to propylene with the above temperature treatments. Kinetic analysis of the IEC measured and the changes of ripening parameters in the propylene-treated fruit showed that: a. Kiwifruit is a unique climacteric fruit which lacks the ability for autocatalysis of ethylene production at low temperature and the limiting factor is rather the availability of ACC production than the activity of EFE, which is responsible for low ethylene production. b. Ethylene production follows the ripening changes and the commencement of autocatalysis of ethylene production proceeds in kiwifruit at 20°C with a relative long lag period (75 h), whereas the commencement of autocatalysis of ripening proceeds with a short lag period (<20 h).