CHANGES IN CHLOROPHYLL FLUORESCENCE OF APPLE FRUIT DURING MATURATION,RIPENING, AND SENESCENCE

Trends in chlorophyll fluorescence for 'Starking Delicious', 'Golden D elicious' and 'Law Rome' apple (Malus xdomestica Borkh.) fruit were ex amined during the harvest season, during refrigerated-air (RA) storage at 0 degrees C, following RA and controlled-atmosphere (CA) storage, and during a poststorage holding period at 22 degrees C. Fluorescence parameters of minimal fluorescence (Fo), maximal fluorescence (Fm), an d quantum yield [(Fm-Fo)/Fm, otherwise denoted as Fv/Fm] were measured , During 'Starking Delicious' fruit maturation and ripening, Fv/Fm dec lined with time, with the rate of decline increasing after the ethylen e climacteric. During RA storage, all fluorescence parameters remained constant for approximately 2 weeks, then steadily declined with time for 'Starking Delicious' fruit, Superficial scald was detected after F v/Fm had declined from an initial value of 0.78 to approximate to 0.7. Fv/Fm was consistently higher for CA-stored fruits than for RA-stored fruits, We were able to resegregate combined populations of ''high-qu ality'' (CA) and ''low-quality'' (RA) 'Law Rome' fruit with 75% accura cy using a threshold Fv/Fm value of 0.685, with only 5% RA-stored frui t incorrectly identified as being of high quality. During: a poststora ge holding period, Fo, Fm, and Fv/Fm correlated well with firmness for 'Starking Delicious', but not for 'Golden Delicious' fruit, which wer e already soft. Fo and Fm were linearly correlated,vith hue angle for 'Golden Delicious' fruit, decreasing as yellowness increased. The accu racy, speed of assessment, and light-based nature of fluorescence sugg ests that it may have some practical use as a criterion to assist in s orting apple or other chlorophyll-containing fruit or vegetables on co mmercial packing lines.