Delayed ripening of ‘Bartlett’ pears treated with nitric oxide

Abstract

SummaryPreclimacteric European pears (Pyrus communis L. ‘Bartlett’) were either untreated or treated with 10 μl l–1 nitric oxide (NO) at 20°C for 2 h and then kept at 20°C. Other lots were treated with 0, 10 or 50 μl l–1 NO for 12 h. In pears treated with 10 μl l–1 NO for 2 h the ethylene climacteric was delayed 4 d, maximum ethylene production decreased by 28% and firmness and colour changes had a 2 d delay. An additional treatment with 10 μl l–1 NO after 4 d decreased ethylene production even further (48%). In contrast, pears treated with 50 μl l–1 NO for 12 h displayed a 719-fold increase in ethylene biosynthesis 1 d following treatment. This sharp increase in ethylene emission, characteristic of a stress response, did not accelerate the normal progress of ripening-related events. In fruit treated with 10 and 50 μl l–1 NO for 12 h, yellowing was delayed 2 d in comparison with control fruit while the softening rate was almost unaffected. Thus, different ripening processes are not influenced in the same fashion by NO treatments. Results suggest a time × concentration effect when NO is applied.