Physiological and biochemical responses associated with chilling sensitivity of 'Fortune' mandarins and temperature conditioning

In this study, we have compared the levels of ABA in the flavedo of 'Fortune' mandarins harvested along the season with different tolerance to low temperature. We have also evaluated the effectivity different heat conditioning treatments to reduce chilling damage and studied the effect of the most effective one (3d at on abscisic acid (ABA), polyamines, ethylene production and phenylalanine ammonia-lyase (PAL) activity. No relationship between ABA and the susceptibility of 'Fortune' mandarins to chilling injury was observed (Cl). The increased tolerance to cold storage induced by temperature conditioning appears not to be related to the induction of ABA, but could be related to fhe increase of putrescine. Conditioning induced marked decrease in chilling-induced PAL activity and ethylene production, which appears to be related with the fact that the induction of ethylene and PAL activity are cold responses, rather than the cause of chilling symptoms.