NUTRITIONAL-STATUS IN APPLES AND JUNE DROP

Apple (Mains domestica Borkh.) trees are often affected by a severe Ju ne fruit drop, which is often correlated with competition phenomena in volving fruit nutrition. This research was initiated to determine if J une drop in ''Gloster''/M.9 apple could be correlated with a diminishe d nutrient availability in developing seeds and fruit. During the test period [30 to 62 days after full bloom (AFB)], the fruit that abscise d had a diameter similar to that reached by persisting fruit 13 days e arlier. Biochemical parameters related to nutritional status of fruit were measured when an abscission peak occurred 38 days AFB. Persisting fruit (control) and abscised fruit were compared along with fruit tha t abscise 13 days later. The cortex tissue obtained from the two kinds of abscised fruit showed a higher level of soluble reducing sugars an d sucrose and a lower content of K+, acid hydrolyzabte polysaccharides , and protein compared to the control. Further, the Ca2+ content was h igher in abscised fruit than in controls of the same age, whereas ther e was no difference when fruit of the same size were compared; Total a mino acid level was similar in control and abscised fruit at the same age, but there was a lower amino acid level in abscised fruit of the s ame size. Histological analysis of cortex tissue indicated that abscis ed fruit have larger cells with less evident nuclei and thinner cell w alls than controls. Compared to control fruit, abscised fruit showed t he same average number of seeds and a severe inhibition of seed growth ; seeds from both kinds of abscised fruit had the same or higher level s of the parameters measured. No positive correlations were observed b etween fruit abscission and nutrient content of seeds or fruit.